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Electronic Repair Questions/Answers And Testimonials- Part32

By on April 12, 2009

hi Mr jestine’


I’m still reading your ebook “LCD monitor repair”.

It is the powerful of information, and beautiful in the style of a step-by-step explanation.

Thank you for this great effort.





I had read your books,plain & match  for me TQ







I really enjoy reading your articles. Thank you so much for sharing!

Hope you are doing well.






Dear sir,

i have purchased LCD monitor repair book yesterday i found it is very useful for me


thanks& regards,






Hi Jestine


I can`t thank you enough for replying and for the information you gave me regarding the part I was enquiring about.I spent hours on the Internet trying to find any info on the IS225 SCR.With one click,you supplied me all the info I needed


Thanks again








Hi Jestine, Thanks a lot. i have downloaded your book and have staretd to read. Pretty interesting since i have just comnpleted a course in basic electronice. this book has already shown me a lot more insights into this field.

From what i have read to date the material is set out in a way that is very easy to understand. Thanks again






I just got the LCD monitor repair guide book and it has lots of helpful techniques.
I’m going to be putting it to good use soon as I have a few LCD screens to fix.



Hello Jestine,

I am very thanksful for having this fruitful electronics troubleshooting articles from a

good mentor like you. I really appreciate for spending your time just to respond my

queries. Your article really gives me a big help to fully enhance my knowledge. 






Hi Mr. JestineYong Good Morning

        Thanks for sending electronics newsletter regularly. Your way of describing the subject is very nice.Each topic you have done the practial work .      

 thanking you





Yesterday I measured the cut out wire from the mainboard to the CRT Tube, and the result is 7.3 V DC. So the heater voltage from secondary SMPT is still ok and the repairer changed the supply from the FBT.

Yes that’s right. That means the tube already have problem and the repairer try to boost up the voltage to make the tube to work again.

I got a Prolink UPS PRO600P from a customer which the battery is already bulged causing some of primary polyester film capacitor changed color from green to black. Seeing this a rather serious problem I borrow our church UPS which has exactly the same type. But looking inside the two UPS, they have different PCBs. Now, after checking the capacitor ( still OK ) and replacing the 12V 7A battery with new one, the customer’s UPS is OK. But to my surprise, our church’s UPS output voltage is only 193 V AC, with or without the battery ( the battery also needs replacing ). Do you know which section of the circuit has the problem?

Sorry no idea about this problem as i rarely repair UPS. Normally i change batteries and fuse only. The UPS nowadays is too cheap that’s why i did not spend my time to venture into this equipment repair. In my company, in a year we have less than 5 UPS sent in for repair but Monitors there are a lot.

Also, it’s interesting to know that when the line supply is off ( customer’s UPS powered from battery ), the output voltage is 258V AC, is this normal?

What i can see is that 193 volt to 258 volt is still normal because most of the equipment nowadays have the autorange. That means input voltage is from 100 vac to 240 vac.

About the coolant spray which I can hardly see in our local store. Could I use the Philips Degreaser Cleaner to use it as a coolant, because the liquid sprayed from it is also very cold.

I have not try that because here we can easily get the coolant. If the Philip Degreaser Cleaner liquid celcius is minus 10 or 20 than it can be use because the coolant have minus celcius which mean is very cold and not recommended to spray on finger and etc.





hi sir

i have download E book already.

and thank God i know about this work but i am new


sir  i have a 14″ lcd monitor and since last 2 weaks four white lines from left to right at different places are appeared and i can not read the smd capacitor’s values please please plaeas help about my probblem.


god bless u


Hi Tahir,

If you got lines across then the problem is in LCD panel. The best solution is to replace the LCD panel





Dear Mr Yong

Due to a small error on my part, I have misplaced the components I removed from my Philips 420p10/00 plasma. I need to know the part numbers.

They were removed from the power supply board where the mains is plugged in:

They are:
1. Electrolytic Capacitor – board reference 2663 (small cap)
2. Electrolytic Capacitor – board reference 2664 (small cap)
3. FET (Field Effect Transistor) – board reference 7610 (may be MOSFET)
4. Fuse – board reference 1500

The above are all from the power supply board (the board into which the main is plugged in). Please help or let me have a copy of schematic so I can see for myself. Help appreciated greatly.



HI Bimal,

Sorry i can’t help you on that because i do not have schematic. Try email Mr kent at fastrepairguide(at) to see if he could help you or not  and hope fully he has the schematic.





Is it possible to use higher capacity capcitar in microfarad . Say in place of 0.22 microfarad can we use 0.33? please ler me know . I am trying to send you money but I will have to wait for my pension money to come. I hope you can understand I do not want money from my son and send.

Thanking you  please reply  Yours faithfully



Hi Ramesh,

It depends on circuit. Some sensitive circuit like the oscillator circuit one has to use back the same value. While to other circuit it has no different. I guess you have to try it out and see.





greetings my friend. remember the mointor with the burnt ceramic cap. that I told you about. it was only 100 nano. I took a wild guess and checked around that burnt cap. found one just like it. replaced it along with the resistor and the monitor passed the test and the customer was happy with it. thanks for your help






Hi Jestine,
I have a lot of waste PCB with a lot of SMD components.But I could not find out whether it is a transistor or a diode.If it is a transistor I could not find out its part no.Please tell me hot to find these things.

With regards,


Hi Santhosh,
Look at the board location. If it is Q then it is transistor and if it is D then is is a diode.





good day! i would like 2 ask if what are the possible causes if d horizontal out was damaged? is there any chance that d flyback will damage also?



Hi Annie,
Please visit this link:





Hello Jestine,
Thank You very much for keeping this site informative and clean. And also adding me in your mailing list. I am A aged 43 as working as a Hardware Consultant.Your site is really making a great help to me .Thank you again,Jestine.




Can you tell me what is the best instrument but cheaper in price that I can use to check

the flyback transformer and where I can buy it.  Many thanks.


The Blue Ring Tester and please visit this article







I can’t say that i have little i have archived since i became a friend to you i would really say that i have a lot i have gained out of the repair guide lines you always send me. But then there is one thing that troubles me and that’s a small problem i have with a TV i recently repaired and the next day i found it only with a red light indicating that it was on but the screen was not lighting, and there was no any sound. I measured the board but found that the circuit seemed okay to me. When i tested it again, the flyback was hissing and in a short time it was a gain off. So the TV won’t start, What would you think the problem is?     


Hi Elagu,

You need to isolate the problem by visiting this website:




thank u! and i read that one of the causes of shorted HOT is shorted internal capacitor in the flyback transformer and i just ask if how can i checkor test the internal capacitor in flyback transformer?




Hi Annie,

Use a digital capacitance meter.





About measuring the heater voltage derived from the FBT, could we use our oscilloscope to measure it, since my oscilloscope can withstand up to 300V peak and up to 100 Mhz bandwidth?

You can try that but i have not tested it with scope before. Perhaps you could tell me the result.

What is the normal range of the G1 voltage?

– 10 to – 70 vdc

What is the voltage when the display is normal ( shows something )?

Depends on monitor

What is the normal range of the 3 cathodes ( R,G,B ).

30 to 80 volts and depends on Monitor circuit

What are the voltages when the display is normal ( shows something )?

Depends on Monitor circuit

Are the three voltages should be close to each other?

Yes normally should be close to each other

What is the normal range of Focus voltage?

From 2 to 8 KVDC and depends on Monitor

Is taking the focus voltage measurement has any significant meaning to us?

Yes to check if the flyback divider is okay or not.

What is the high voltage component ( like tantalum capacitor and has light brown color ) located in the CRT board?

Normally i don’t see tantalum capacitor in CRT Board. What is the board location and which area did you found these caps in CRT?

I always see the CRT board has some of them. In the schematic they are connected each from RK,GK,BK, G1, G2 to ground. What is the use of them?

Are you referring to spark gap?

When I see desoldering process of SMD IC at youtube, they always brush the pins first with liquid, what exactly is the use of this liquid? Do you also use this liquid first before desoldering?

If i’m not mistaken it is like a kind of liquid type solder flux paste where when you want to apply to the ic pins, it will automatically stick on the pins-easy job! I do not use that type of liquid.

Do you ever have to replace the CRT socket when servicing,

If it cause intermittent problem then i will replace it.

is this CRT socket easy to get?

I normally salvage from junk crt board and crt socket rarely give problem.

I can hardly find this socket at the local store.

Even my local supplier also do not have but they do have the TV CRT socket.

When accepting the monitor from customer for repair, do you usually say to the customer when will the repair be done?

Normally i will tell them 3 to 4 working days excluding saturday and sunday

Do we always need to say this?

I say this only to new customers.

Also, do you usually tell the amount of cost first to your customer?

I have fixed the price for Monitor repair so that this will easy for them to quote customer. That means if i can fix this Monitor you need to pay this amount and if i can’t fix the Monitor then is FREE OF CHARGE.

Do we always need to say this?

Say this only to new customers.





greetings, hope this message finds you well. I have a question for you. a monitor came to my shop today with the problem that something was buring inside it. I checked it out and found this ceramic capcitor was was half burnt next to a resister that 2ohm that has a whole in it and the colors changed on it because of the heat. any way, my question is, the capacitor that is half burnt has this writings on it. 250MEF1. what does this mean. I found another capacitor that almost matches the original but some differnces 250MPP1. my question is can this be a replacement for the burnt one? please let me know. Thanks


Hi Waleed,

That stands for the working voltage which is 250 volt and you need the capacitance value and it can’t be substitute  with another 250 volt cap with different capacitance. In other word you need to find out the capacitance value thru schematic and etc.





Hello Mr Yong,

I have another question.   I am working on an older Funia television.  The HOT is an D2333.
This Q has a damper diode,  I understand normal transistor tests ( ohm & diode) are not accurate when there are dampers and biasing resistors.

I am using a homemade VI Curve tracer and it shows that this HOT is shorted B to C , B to E and C to E.

My question”  is a VI curve tracer an accurate test for these types of transistors? “


Hi Laplante,

From your description it is obvious that the HOT already shorted. However  i suggest that you compare with a known good HOT and jot down all the important reading of a good transistor. With this way you will know if your own home made VI  curve tracer is accurate or not. I have the Huntron 2000 VI curve tracer but i did not use it to check on HOT. Normally i use analog meter to test it. Hope this helps!





I talked to Samsung Company and Rep said 2 motherboard (Board with power port) has P/N or (Board with VGA port) has ?? P/N ??. I need know what problem “Not Optimum Mode: Recommended Mode: 1280 x 41024 60hz” do you know which one motherboard?




Hi Daniel,

The board with the VGA port and the P/N number you have to read it from the board printed either in front or the back of the board.





HI Andria,

So I have to remove the capacitor from the board first and then discharge it? I’m just thinking about what you said about connecting the 100 watt light bulb directly to the 2 pins and since they are in the board it sounds like in order for me to get to the pins they must be removed first?

No need to remove the cap, you can discharge from behind the board and directly to the two pins of the filter cap.

I would think you’d want to discharge it before touching it.

Yes you have to discharge it before doing any repair work.

But it doesn’t seem right to flip the board and put the light bulb over the sodered capacitor eithe. Can you elaborate on this a little further?

If you can access from the front then you discharge it on top of the board without flipping the board. Remember, after the discharge make sure you test it with your voltmeter before starting doing the repair work.

Also must I discharge all capacitors even the ones that are not faulty? Thanks

Discharge only on capacitors that have rating of 100 vdc and above. Some caps will discharge by the circuit itself after power off.

By the way i will be on holiday starting tomorrow and can only check on the email on Sunday night.

Best regards,




Hi Yachad,


You really helped me.

Sorry i have “missed ” out your email


I got my first real customer who sent me 12 ATX PSU’s to repair.


They were relatively easy – just replace all the bad caps with new ones, and they worked all OK.


After a month, he sent me another 6. 4 were just cap replacements, now the 5th one was a real challenge.


Picture attached.


The fuse had exploded, so I put in a new one, and connected AC in series with a lamp.


I switched it ON, and as expected, the lamp illuminated.


So, there was a problem in the primary side.


I traced the problem as follows:


One of the 2 680uF/200V filter caps was open circuit, which apparently caused a failure of both the D13009 BJT Power Transistors and one of the 4 RL207 rectifiers in the bridge.


I replaced the 680uF, the D13009’s with 2SC5763’s, and the one RL207 with an RL205.


Then I switched on again, no lamp (good – the primary is now OK), but a bad smell.


There was a burnt resistor.


I measured it at 22Ohms, but I don’t think it was 22Ohms, because the first stripe looks brown. The 2nd and third stripe are completely burnt.


Anyway, I put in a 22Ohm resistor, just to test.

In the picture, you can see a Burnt Resistor 22Ohms


That burnt also, and after I removed it, I measure it at 12 Ohms now.


One pin of this resistor is connected to the AZ7500BP Pin 12 Vcc, and the other pin to the Cathode of a diode which comes off the transformer at the left-front.


All the caps are OK on ESR.

Diodes around this resistor check OK.


Any ideas what to do – now I am lost!

It could be a 100 ohm or a 10 ohm resistor since the first color band was brown. Try remove the 7500 pwm ic and check whether the resistor burn again or not. If not then replace the pwm ic and retest again. Since the pwm have internal circuitry that links to external component, you are require to check on those corresponding componenst too.

Many of the smsp are quite similar except that the designers may just have place the circuit the other way round but function is the same. That meeans you can compare with other type of SMPS that use the same pwm ic which is the 7500 and trace it at pin 12 of the ic.

Hope this helps!

Best regards,





Yes, I could be measured with my scope. It originally had two turns around the FBT, so I took the measurement also with two turns. It read about almost 6V, the freq was also written on the display. See the attached photo.

Wow! you got a very nice scope. May i know what is the brand of the scope and how much you bought it?

Sorry, the designated SG38X components located in the CRT board looks like tantalum cap, but they are not tantalum capacitor.

Since I had reassembled the monitor, here I show you the components in the schematic, they are connected each from RK,GK,BK, G1, G2 to ground. What components are they? What is the use of them? Please see the attached photo.

They are the spark gap and use to prevent any arc over in the internal electrode in the picture tube.

Are there many types of CRT sockets being used in CRT monitors?

There are only few types for the 14/15″ and 17″. Basically the different is the diameter as some tube have smaller diameter.





Hi Dwayne,

I have been through your website and i found that it were really
interesting base on the books which you have published.i am now thinking about ordering
one of your book

Thanks for the support!

i am now working on a TV set in which the flyback transformer is overheating
i suspect that the problem is with the HOT D2539 when testing it shows continuity
on all three pins

If show continuity on three pins this mean the HOT already shorted. Please check on other components too like primary winding of flyback before put in a new replacement and “On”.

can you test SCR ,IC and capacitors with the ohm and diode range on the DMM?

Yes you can but not accurate.e-cap i test with ESR meter, IC using scope and SCR with analog meter.

i guess when i buy your i would not be asking this question.

If you have bought my book i will encourage you to ask me more question to make yourself a professional electronic repairer.





Hello Jestine

just wanted to say again thankyou for your books they are great

I have a question about laptop inverters.

What usaly goes bad on them and how can i track it down with a volt meter

Any help would be great


and have a great day.



Hi William,

It can be dry joints or bad components the best is to make sure there is supply voltage to the inverter ic.





hi Jestine

Saya ade CRT monitor Benq 17″,masalah display kembang dan kuncup,harap dapat beri tips.Terima kasih

Hi Ahmad,

Kemungkinan internal capacitor dalam flyback dah rosak ataupun kerosakan pada filer cap dekat smps power supply.





Thankyou, Mr. Jestine Yong,

I am beginner in repairing monitor. For this time I tried to repair my computer’s monitor.

The problem is: The screen of 15 inch Dell computer’s monitor always blinking fast ( cannot stop). I tried to change and adjust potensiometer near the flyback transformer it seems OK, but if I swith off then switch on again, the monitor again blinking (still not solve the problem). It seems signal from computer is good because I saw, Windows can start normally but the picture on the monitor always blinking.

What components or how to solve my problem ?. It is  1.5 months I cannot repair it.

Thank you for your kind answers.


Best regards,


Medan, Indonesia


Hi Burhan,
Try use the isolation method in this link:





It did actually work and it did help me a lot. Am sorry that i may seem to be bothering you but i have another small problem i would like you to help me with. It’s a 21inch TV when turned on it brings a green color and after sometime the pictures are back to normal, the color covers the whole screen.   


Hi Albert,
From your description, it seems more like a dry joint in the green section of the CRT board.





Dear Jestine,

please teach me the best way to work with rework station….


The best is to try it out on used motherboard.





Hi Joe,

Can one test an Integrated Circuit Chip before soldering it to a PCB?

Yes you can but it is not accurate because ic consists lots of components in it. The best to test is to power on the equipment.

If so how does one test a chip and what instruments are required to test it? Are there any internet sites that deal with this subject?

Best regards,




HI Hendrik,


i already buy your lcd repair ebook.

Thanks for the support!

by the way physical book talk about what? hope about lcd/crt monitor.

It is troubleshooting and reparing SMPS


i have question for lcd repair ebook page 21 understanding power supply board .


why after smps transformer back to feed control circuit and swtihcing power ?


for what purposed all back to switching power  not power output 12v , 5v ?

To maintain its regulation. Without this feeback circuit the output tends to increase or decrease and will affect the picture and overall performance.

Best Regards,
Jestine Yong





hai jestine


i forget to ask. my friend have scope analog and digital but price digital twice expsein


which is better to use? analog scope brand tektroin us$100 and digital i not sure what brand  us$200 .


usuall mr jestine use what scope?  analog enough?


give me suggestion?





HI Hendrik,

I have the analog scope and no intention to get digital scope because analog scope already serve my purpose of measuring waveform. If you have the budget yes you can get the digital scope and make sure the frequency is 100 mhz and above.





Hi, Sir

 Thank you for your info about CRT Monitor Blur solving method.

Currently Im working as technician in Molding field,the m/c panel monitor using CRT monitor and already 30 over years old.

At present we’re facing screen blur and the colour not in order ,I had adjusted the B,R&G Cutoff regulator to optimize the colour back to original and also rotated the magnet on tube which secure with two clip.I cannot get clear colour and picture compare to other monitor.


As you mention about fly back transformer modification,isit can apply for this type of problem or please advice.


Hi Nantha,

From your description i guess the picture tube may already weak and my method would not solve this kind of problem. My method is for the screen that is in good condition except that it slowly get blur.





I am currently working on sony T29MF8S. When turn on the unit it has sound and no video, it went to standby in 2 sec. before it went to standby I saw green spot on the center of the screen. what section or components should I focus on?? Thank You


Hi Michael,

Try check if the pc tube yoke coil is connected to the board or not and also dry joints in the area too.





Hi Jestine,
Thank you for the nice offer, definite I will rely on you for guides . I have just finished reading the “first” round of the e book yesterday and am reading it again this morning. It’s like a new frontier to me eventhough I did have some lessons on electronics 25 years ago. Wow can’t stop reading it, very very informative . It was not like this when I tried to pick up the subject when I was “young” then.
I remember in 1984 when I once worked in a hotel, we have tvs in every rooms, 409 in all to be correct. After the warranty period the tvs was down one by one. So we called in the TV technician and we tried to catch what he did to the TV.
After that when there are units which showed the same symptom like the last unit, me and my colleague play “tikam-tikam” (guess work) to repair the TV. Never in our life thought of the dangers of being electrocuted – (kay kiang). But after reading your e book I am more carefull. Thanks Jestine for the reminders.
I am going to finish the e book and read the rest of the bonus reports.

Cheers and best regards




Hi Jestine,


Just got my first PC Monitor in for repair – AOC 17″.


I was quite lucky – I diagnosed the Horizontal Deflection Transistor short-circuited, in about 2 minutes.


It is a Toshiba 2SC2855.


2 questions –


1. Is it OK to replace it with a Philips BU2515?

2. Should I be looking somewhere else on the circuit to see if something else caused the HDT failure, and if I put in a new one, then maybe it will fail again.




M Yachad


Hi Yachad,

Try this link

I’m not sure about the replacement number-i guess the best is to use back the original number. I think the original part number you have given was wrong, it should be a 2sc5855.

Have a good day!

Best Regards,





Dear Mr. Yong,


We have a car dvd player with a 7″ screen, the player plays sound, and works fine with an external monitor, the problem is that built in monitor only shows a white screen and the buttons connected to the white screen also do not work. On the other hand, the buttons connected to the bottom of the player (not the screen) work fine, I have tried the solutions for white screen from the E-book, but I can not manage to fix this.


Now there are a few PCBS, two inside the player and one behind the screen, could you please help me out and tell me what can be causing the problem?





Hi EZ,
If the voltages and waveform from the mainboard are present to the lcd controller board then suspect a bad LCD panel. The cause of the problem were mainly the lcd controller chip that do not process any signal to the LCD DRIVER ICs thus only white screen appeared. If you have other question please do email me again.





I hope all is well Jestine

I am reading through your manuals and am looking for help on a LCD TV
problem. 19″ Unit and it works just fine until about five minutes.
At that point, only the sound goes away and the rest of the TV works
okay. Picture and channels are all good and just no sound. I am
trying to find what area of the board to focus on to test. Any advice
would be appreciated…thank you and happy new year.


Hi Randy,

I suggest that you trace back from the speaker until the audio area. Check for supply voltage to the audio power ic and if possible check for the waveform too.

Best regards,




hi jestine !!! i am rizwan from pakistan and also your one of the member
i have a lcd monitor L1800 from HP the problem is that when i powered the lcd monitor the interferrence lines in magenta appears and it is running in between lcd screen or whole screen i dont recognized this problem is this the problem of emi filter because the lcd power supply is connected with EMI filter or this the problem of dc supply adaptor or this lcd circuit problem .can you plz explain me to this problem why these interferrence lines appear in lcd screen and how i corrected this problem.


Hi Rizwan,

The best to solve this problem is to use a scope and check on the secondary output side. If you did not see any interference then suspect a bad main board or even a bad lcd panel. If you could see lots of interference then check on the power side. Hope this helps!

Best regards,




Dear Mr.Jestine,Problem with Canon Printer SMPS. The printer cannot turned on,
after I checked, the problem is at the power supply.
The healthy SMPS has 7.1V on the output, but the fault one only have 5.6V on
the output.
I have similar power, and I already exchange all of the component, but still
the faulty one never got 7V on the output.
I already test each of the component, exchange it one by one from the
healthy one, but still cannot solve it.
Would you please help me sir?

Thank you very much.

Best regards,


Hi Julianto,

Have you test the filter capacitor with ESR meter? As bad filter cap could cause output to become low. What about the primary side current sense resistor? If the resistance of the current sense resistor increase it will cause the output power to become low.





hi jess,
i am  so impress  to  your generosity of giving support to upgrade young technical man
like me, again my warmest salute on your open-handed heart for us,”







Dear Mr. Jestine Yong,


Good morning, I received and read your mail.

The First, Thankyou very much for you.

Your infomation supplied for me, is excellent. I don’t know to express one’s deep gratitude to you. I only know thankyou and thankyou … you


Best Regards,




Hi Jestine,


Terime Kasih kerana tips, Saya nak tau samaada IC 4600 (LCD Samsung 15″) boleh didapati dipasaran tempatan, Terima Kasih


Hi Ahmad,

Saya ada kawan yg jual IC ini tapi sekarang sudah tiada stok.






HI JESTINE, whaid i need your help,iam working on power a power supply for a samsung plasma 42″ tv what happen is it has two FET s burst open the # is FQPF9n50C the problem is i can not locate any in our countary any sugession what i could use . ………….thank you


Hi Whaid,

Try to find from the list of eelctronic suppliers here:





Thank you Jestine.  That gives me something to use as guideline.  When I email you, it like your suggestions instead of telling me what’s wrong.  I fix monitors for fun and to make a few dollars so learning each problem and how to fix it is important.




Hi Randy,

You are welcome  and if you have other question please do email me again. Many times electronic problems are dynamic that’s why we need to learn how to find out the fault instead of just direct to the component. There was a saying “If i give you a fish you will eat for a day and if i teach you how to fish you will eat for life”. Have a good day!





HI Zed,

Good pm sir, may you enjoy your trip to relax and unwind.

Yes it was a fabulous trip!

i would like to ask if it is the test B861 SILICON PNP TRIPLE DIFFUSED IS THE SAME TEST of a normal transistor or not?

Yes it is the same test like normal pnp transistor.

it is said in the data that it is for vertical function?

From experience this transistor mainly locate at the secondary side of power supply. Perhaps the designer may use it in the vertical section.

i test it in the diode function of my digital tester when i get the base to collector(flange) it read .567 and base to to emitter it read .566 but when i put my probe to collector to emitter .000 reading even you reversed it. even in analog meter if i get the base i have low reading both on the collector and emitter. but when i put the probe to collector to emitter i get near zero evn reversing it. does it mean it is shorted.

Since i do not have this transistor at the moment i can’t tell you the result. The best is to get a new transistor and compare the result and jot down all the readings be it using digital or analog meter.

i find it in a crt monitor AOC the led light to green but there is no display. it has a history of curving the display in both side and you said if that is the symptom look to pincushion circuit. i find the other pin their that is cracked so i resoldered it again and when i turn on the monitor again the display curve gone and no display at all. this transistor is located in pincushion circuit  if im not mistaken near the horizontal circuit it is attached to the heatsink where the ff. components are attached also to the heatsink F08A80 DIODE where the negative pin or cathode of the diode is going thru the collector(flange) of B861. I would ask for some technique how to troubleshoot this kind of trouble.

Yes it is true if curve then look for the pincushion area but the monitor problem now is no display with green led on. Does the Monitor have high voltage? Is the B+ voltage entering the flyback pin? What about h. drive waveform to the base of the HOT. Without these two signals there will be no display.

The flyback is good i test it according to your three step. the HOT is ok also. this b861 i am doubtful.

Normally flyback will not cause pincushion problem. HOT is okay because you already got the display.

Best regards,
Jestine Yong




HI Jonathan,

hi sir jestine, this is jonathan from philippines,

Nice to know you.

i don’t have enough knowledge on repairing laptop but i do repair PC, i hope you can share me some idea on how to repair Laptop..

Ok no problem

because of my busy days, i don’t have much time reading your blog..

No problem-but read it when you have the time as the tips will greatly enhance your repair knowledge-after all it is free.

.my problem is, i have a laptop here it is HP Compaq presario 1240.the problem is no dispaly on LCD, but the VGA out is operating what is the posible cause of that trouble?

It could be loose connection internally. The best test is you must make sure the inverter ic in the inverter board is getting voltage. No voltage means the display will be very dim and you may thought it was no display.

hope you don’t mind sharing me some idea sir jestine… and what is the output voltage going to the filament of LCD..

LCD backlight do not have filament inside. It has gases just like our house fluorescent except that it runs on a higher frequency so that it is flicker free. The output voltage from the inverter to the backlight should have several hundred volt.





HI Hendrik,


what scope do you use?

I’m using a Kenwood 50 Mhz bought more than 10 years ago. I did not upgrade the scope because it already serve the purpose. However if i got the chance to get a cheap digital 100 mhz scope then i will go for it.


my friend offer  me scope teknorik 100 mhz analog us$100 or japan brand digital scope 100 mhz us$200?

If you have the budget get the digital 100 mhz scope.


can you please advise which one suitable for me in printer repair and monitor repair ?

Both scopes can be use on any electronic equipment repair.


i am in printer repair field have any ebook about printer repair?

Since i’m writing my fourth book, William have to put on hold his ebook project which talks about refurbishing printer head because he needs to take care of the company while i’m at home writing the book. . Once i have completed my book then only his turn to write his book and i will take care of the company. He also told me that once he had completed the refurbishing printer head ebook he will continue to write on laser printer repair ebook but i do not know when he will start on that project.


Best Regards,





What are the common spare parts used repairing LCD’s.

Capacitors-again it depends on what kind of brand you are repairing

From your experience is it cheaper given the cost of spare parts or to recommend purchase of new LCD.

It depends on the problem as some problem only caused by dry joints and few cheap components like capacitors


What should i look at when buying a second hand or used LCD or

Laptop from Europe to AFrica?

Look at the screen and the manufacturing date. Make sure the screen is not scratch and the date of manufactured is not more than few years.


Printers: Considering the cost of ink, would there be a new technicology )not refill because this one damages the cartridge over a period of time) where ink can be cost effective. What are tomorrow’s printers where small business are concerned that will be economic to the small business and for community work? We need design economic printers. Any solution please advise.

So far at this moment the best color printing is still using the cartridge technology.

Best regards,




Hi Zed,

thank you sir for your answer. i buy new b861 transistor and it show that the old one is shorted bcoz the new one has no reading of .000 on  c and e even if you reversed.

Remember to jot down the reading for future reference.

but when i install the transistor and turn on the monitor  the led light to green but there is still no display and some tic tic tic sound on flyback. i check on the primary again thru dick smith flyback tester and it has only one red light i think the flyback gone into its final life.

If after the removal of the flyback from the board and still got one reading then the primary winding had shorted.

i check on the internal capacitor and it show 2.69 nf and it is range according to your tip. i check also on x10k of analog thru anode cap of fbt and its pin and its show no reading at all.

That was a good reading for the internal cap.

i think the primary winding has given up. is my test accurate even i did not disconnect the wire of focus and screen on crt circuit when i did the test of my fbt?God bless you and your family.

You are welcome!

Best regards,




Hi Jestine!

Even though your monthly news letter is very helpful on board repair, I still have to come back to you for a little help. I have a driver board for a drive which is VFD. Every time I powers it up, this little voltage regulator IC chip goes bad. It is a three-terminal low current positive voltage regulator with a part number 78L00A Series. Some times I hear it burn, some times I don’t. The burn comes from the input leg which makes me wonder, there is an over current coming into the chip. I tried to trace it back but no luck. Can you please advice me on this. I know you are an electronics doctor.



Hi Ermias,
Try remove the voltage regulator and check the voltage upon power “On” the equipment. The voltage should not exceed 38 volt and test it with analog meter because it can capture the reading faster than digital meter. If it exceed the voltage then check on the power supply side. If it does not exceed, try connect a few ohm 2 watt resistor in series to the input of the voltage regulator to limit some current upon switch “On”. If it still burn try  remove the third leg and power on, if the ic did not burn then suspect the load have problem and this you have to use your repair skill to find out the leaky or shorted component. Have a good day!





hello and thank you very much for your monthly news letter..sorry i am still earning money to buy your ebook…can you help me again sir for my problem with my benq lcd monitor? the problem is that when i turn on the unit i can see reddish video and after few seconds the unit will turn off..i check all capacitors and its okay the transistors are okay what  is the problem ? thank you and hoping for your response….lito 


Hi Lito,
reddish screen and shutdown usually indicate problem in the backlight. Hope this helps!





Yes Mr. Jestine, I agree with all your ideas,.

Honestly, what I know after read all from your website are:


1. Soon… I saw your photo, I believe you are a good man & smart. Your photos makes me to remember to see again the many kinds of Malaysian people. I was in Malaysia for two months a year ago.


2. Your letter in website makes me get some hopes to increase my knowledge in repairing electronic. You are also a good teacher.


3. I downloaded all your letters in your website, saved it to my flash disk  and last night I read it all at  my home. Slowly,  I read and understand what you meant in your letter. As you know I am not so good in English but you can explain with an easy language to understand. That is I thing your another good point.


As what I have written in my letter before,  I am a beginner even I have learn long time years ago from the book & tried to repair my self  electronic equipments. But still cannot understand how the easy  way to increase my capability. It is very difficult to me to find the secret to become a talent electronic repairer. Yes .. many books just explain the theory.  I have never seen a book like your letter in website to guide me an easy way to understand electronic repair. Thank you  for your kind to share your experience to all peoples in the world.

Nice to know you and thanks for the compliment


The other things thats makes me sometimes frustrated to concentrated to study in repairing electronics are:


1. Now, many electronic manufactures makes the PCB not only 1 layer but also 2 or 3 layers. How can I solder components into all the layers?. Do you know how to solve this problem?.

Use a  solder gun like hakko 981 that have 130 watt and also apply some soldering paste too.


2. How the easy way to redraw the PCB into a paper if I cannot get from internet?. Studying the wiring diagram more easy for me to understand the princple of PCB operation.

It will be difficult as this kind of board have so many layers-only the manufacturers have the diagram and most probably they would not share out.


3. Electronic components become more-and more small in size. It is very difficult to soldering by hand. How to overcome this problem?.

Use a rework station with the help of tweezer.


If I am not wrong, your book’s price is $120, is it?.

Yes the Testing Electronic Component ebook price is RM120.00 and LCD Monitor Repair is RM150.00.

Hopely I can buy your book at beginning date next month.

Thanks for the support!






Hello sir,

I have a SAMSUNG LCD monitor with a red color dots(2 to 4) in the that normal or is a fault??

I bought it before 3 weeks…
plz advice me..



Two red small dot means stuck pixel and try use your hand with the help of a cloth and gently press and rub on that area hopefully it will go away. Please do not use force until the screen could crack. Hope  this  helps!





Hi Yachad,


Thanks for your reply.
No problem!


As I mentioned, this is my first monitor repair (AOC FT700), so I am learning with every minute.


Attached is a photo of the PCB.


You can see that I desoldered the 2SC5855 HOT (you were right – my typing error) and on the flyback transformer, I have marked in Red, where I think there is a short.


Pin 1 – 2 is 0.82 Ohms

Pin 1 – 3 is 0.71 Ohms

Pin 2 – 3 is 0.42 Ohms


All the rest of the Pins are in the kOhms range.

Pin 1 and 2 is the primary winding and not shorted and pin 3 is not connected (NC).


I don’t have a Ring tester, but would you agree that there appears to be a short here, or are these Ohm resistances on pins 1, 2, and 3 normal and OK?

Resistance check is not accurate and you need a ring tester to check it out. Pin 3 have no connection.


On my AADE LC meter, which I use instead of a Ring tester:


Pin 1 – 2 is -10uH (Minus)

Pin 1 – 3 is -7.8uH (Minus)

Pin 2 – 3 is 0.17uH (Plus)

A shorted primary winding can have a good inductance reading and due to this i never use inductance meter to test out the winding.


If you look closely, the solderjoints on Pins 1 & 2 look cracked – I resoldered all of the Transformer joints.


If the flyback is shorted, I’ll have to junk this monitor, because I can’t get such a spare flyback!

You have to get the ring tester to check it in order to confirm it.


I’d like your opinion on this possible short, before I replace the HOT, so I don’t just waste it.


Well it can be other problems that cause the HOT to short as mentioned in my blog but if you know that the primary winding is good then you can concentrate on other circuits or components. If you are doing full time in electronic troubleshooting then i guess you need to invest on one of the ring tester to save your precious time in electronic repair.

Best regards,




hi jestin.

thank you very much for your informative site.

one question:

is the blue esr meter best way to test electrolytic and ceramic ( highter than 100nf) capacitors?

have a good time.


Hi Saeed,
Yes from my experience the Blue ESR meter is most suitable to test the caps you mentioned.





HI Maung,

Hi! My name is (Maung soe myint). I just join your team. Mr. jestineyong: Thanks very much for all the information and ebooks. It was very helpful. I am start learning about repair LCD & plasma tv.

Nice to know you.

I do have one Zenith 50″ plasma: not working: model-P50w26b: I just get from my friend its not working. When I took apart and check the fuse was blown (open). It was 250V 8amp fuse. I put new one and as soon as hit the swith On. its blow the fuse and shut down.
I would like to work on this Zenith: If possible please help me for information about (Service manual-for Zenith 50″ model-P50W26B). If you have please let me know, Do I need to buy for download or any potions.
Also if you have time: some hint for start troubl shooting.

Sorry i do not have the schematic. If the fuse blow again have you check the bridge rectifier and the power IC/FET for short circuit? Sometimes a shorted diode in the secondary side could also cause fuse to blow too. Hope this helps!





Hi Jestine


Thanks for the info in your book.Helped me a lot since i downloaded the book

Adriaan C.



Hi Adriaan,

Glad that you like my book. As for the replacement part i guess this website could help you on this:

Best regards,




Hi Jestine,  I am back here in New York trying to solve this problem with a Dell TFT LCD flat panel monitor. Usually when I have a problem, it is the 2SC5707 transistors that drive the backlight inverter transformers. There are several similar LCD monitors made by BenQ for Dell Computer.

The monitor I have now is made by Liteon for Dell. It is a Dell model E172FPt and there is an additional model number of CN-0J1806-71618.

The problem is when you turn the monitor on. The front panel light comes on and then flashes on and off and the backlight for the LCD panel won’t come on.

Usually in this case I replace the 4 inverter transistors and resolder any cold joints, but I was wondering if you had any other experience with these monitors?


Tom in New York


HI Tom,

Led flashes usually indicate problem in the power supply. Try remove the pico fuse (if have) and power it on again. If now it doesn’t  blinks anymore then suspect power problem and if still flashes then suspect the inverter board problem.





 please send me some information about the fuctions of electronics parts, for example: a transistor; what does it do in a electronic circuit and so on… I will be very thanks full to you in future and will be keeping contact to you..


Hi Rajan,

For all the electronic components theory you can find it at google just type in these keywords like:

“how transistor work”
“what is transistor”

and you will get lots of information there. hope this helps!

Best regards,




greetings to you my friend. something really strange happend today and it would be nice if you can explain it to me.

I had this mag monitor that worked really good with my computer but when I tried the same monitor on other computer, the screen was red and it shuts down. but on my computer, it worked fine and for sooo many hours. the only thing that I noticed is when I turn the monitor on, it has a redish color but it gets better later on. any explanation for it? I have fixed an lcd monitor with reddish color which was due to a bad back light but I did not see anything wrong with this one. please help


Hi Waleed,

Most probably could be due to the graphic problem. I had the same problem like yours which was a Likom Monitor and after downloaded the latest software from their website the Monitor worked perfectly good.





Hi Saeed,

when a rechargable battery is discharged is the esr of it increased or the esr only increased when the battey is expired?

It depends on what type of battery you are testing. The best is to compare a good battery with a bad one.


2) can i find an electrolytic capacitor with leakage problem with the blue esr meter in circuit? ( do leakage increase the esr of capacitor?)


Yes you can find a capacitor with leakage problem with blue esr meter if the leakage already become severed. If it just slight leakage it may not be able to detect it. Normally when i see a leakage capacitor i did not test it with the esr meter instead i will just direct replace it and retest the set again.





2nd Question:
I have a meter called “Protek 506” is a nice meter, i been using it for a about a year.
the meter can test Resistors, Diodes, Capacitors, Coils, Logic, and a lot much more, etc.

There is one feature i like about this meter, the Diodes and Transistors measurements.
So when i test a diode or transistor it give me a reading as fallow: Short, Open, Good.
i been doing this for about a year now and i been able to fix few electronic components.
But then everything changed for me when i started to measure “Schottky Barrier Diodes”.

When ever i test a “Fast Switching Schottky Barrier Diode” i get a reading like if the
diode is bad even if the diode is OK, the same thing happen if i use my analog tester,
i get a reading on both directions, i always used my analong tester specially to test
diodes, but i have never come across with this kind of readings, this is something new
for me now, i know schottky diodes have a very low tricky voltage and can confused any
tester. So to get arround this guessing problem when testing these diodes, i got me an
“Peak Atlas DCA”. Now here comes my question, can you please tell me how exactly can i
tell when a diode or transistor is bad or good just by pointing to their drop voltage?
Please continued reading…

I have a Schottky Diode i am testing with my analog tester and also my Protect 506.
on both tester i get a faulty reading telling me the diode is bad, but i know is not.
So here is a reading i am getting with the Peak Atlas DCA:

Type of Diode: Fast Switching Schottky Barrier Diode.
Reading: Diode or diode juction(s) – Foward voltage VF=0.19V – Test current IF=5.26mA.

I would like to know the lowest forward voltage drop of real schottky diodes or the
highest voltage drop of diodes so i can be 100% the diode is good or bad.

I also get confused when i test some diode networks or some led transistors, i been
wondering what exactly have to be their drop voltage in order for me to tell is they
are good or bad. my confusion come when ever i see a reading of a drop voltage like
this example right here:

LED or diode juntion(s) – Foward voltage VF=3.52V – Test current IF=1.61mA

I liked the “About C5707 Transistor Replacement In BenQ T705 (Model Q7T4) 17 LCD Monitor.
there you explain about using the Peak Atlas. something about the: HFE reading in the Peak.
You said that replacing the one with the reading of 350 to 400 solved your problem.
so in this case you know what to espect when it have to do with the HFE, well the same thing
i would like to know when reading the Foward voltage drop and also the Test current.

I will be very happy if you can teach me about the “Foward voltage” and “Test current”
when using my Peak Atlas DCA.  Thanks Jestine.

Normally i do not test diode and transistor with digital meter because i had come across these semiconductors were tested good but failed when i test it with analog meter. The output voltage from the analog meter is higher than the digital meter. I don’t always look at the forward voltage or test current but always jot down the experience after comparing the result between the analog and the digital meter. My conclusion was that test the schottky diode with analog meter set to X10 k ohm and it should have two readings but not shorted reading. The best is to compare the reading of a leaky/shorted schottky diode with a good working one.




3rd Question:
I have a tester called “The Capacitor Wizard” is an analog ESR capacitor tester,
I also have a digital capacitance meter specially to test any capacitor except esr
like the capacitor wizard, but then after using these capacitance tester for more
than a year, i started to have a doubt about the reading in esr ohmn in capacitors.
So i end up getting me an “Atlas ESR”. Now i don’t know if you are familliar with the
Atlas ESR, but here comes my question, I have 5 16V 470uF Capacitors that i took out
from a TV, i get the same reading from all these 5 Capacitors, so here is the result
from the Atlas ESR:… Cap = 506.6uF – ESR = 0.04 Ohms

Acording with the Atlas ESR table, a 16V 470uF should be: 0.35 Ohms
so what do you think about this measurement?   Thanks Jestine.

Here is a chart that is very good for reference and any value that less than the one in the chart is consider good.

so in your case 0.04 ohm esr for the cap is good.


And finally my last question:

“The Ceramic Disc Capacitor Leakage Testing Secrets”
I liked this example you gave on how to accurately measure high voltage capacitors.
in this page you advise us to use this tester: “Kyoritsu 3111V Insulation Tester”
but even on eBay this is a hard to find tester and if you find one still expensive.
so i find this other tester that it does almust the same thing as the: Kyoritsu 3111V.
Here is the link if you want to take a look:
My question is, what do you think about this tester? do you think is a good second option?

Yes it is good after reading the spec.

Best Regards,




Hi Jestine,


How are you?


I am working on Panasonic TC-14L10K and found the Zener Diode was shorted. However, the is no number on the diode itself only only white color around the cathode side. ( this diode is really small)


so, I look around other same size zener diode has the same white, and some of them are light blue. How do I determine the voltage. Should I use resistor color code??



light blue–6v


Please Advise


Thank You




HI Lee,

Since you have the same type of zener diode then measure the reading and jot it down. Then get few zener diodes like the one you mentioned 9 volt and etc and compare the reading. If the reading is the same with the one that you have jotted down then you will know the zener voltage. Hope this helps!






KIA431 can’t be test with meter measurement unless it is directly shorted. The best test is the direct replacement

Best regards,




Dear Jestine,

I’ve just got this monitor from customer, the problem is the display off the centre, and cannot the positioned in the middle even using the position function and the left edge is not straight. To my surprise, only two of the display functions can be adjusted, they are contrast and bright; every time when I switch to the position function to centre the display, the relay works and it cycles again to the contrast function as you can see from the photo attached. Could you give me a hint about where & what could be the problem.

How could we know exactly which circuit is associated with each of the display function; especially if we don’t have the schematic or manual? I think this info is very important if we want to solve the problem faster and to excel in this monitor repair field.

Hope you could help me with your reply, as I’ve already opened my repair shop and begin to receive the bad monitor from customers.

Thank you very much.



Hi Bailing,

Congrat on your new repair shop and hope more customer sending their bad electronic items for you. About the Monitor, it seems that it could be eeprom problem because so many other functions were not functioning. However please confirm that the cpu and it related circuitry does not have any dry joints and make sure also the cpu is receiving a stable 5 volt supply.

As for your other question “how could we know exactly which circuit is associated with eash of the display function especially if we do not have the schematic?”

The answer is to if posible get  a Monitor that have a schematic and do your own research like by removing components and see what the display like. For example, try remove a capacitor in the vertical ic area and see how the display look like. Of course this will take some of your time but i can say its worth it. In some analysis you may shorted some of the components but never mind you have the schematic to help you fix back the monitor besides you could learn from the problem too.

If you have other question please do email me again.





I hope this email finds you in good health.  I am trying to diagnose a Logic CRT TV.  The source (outlet) AC voltage (220V) is present every where on the primary side of the power supply.  All the four pins of the single packaged bridge rectifier measures that 220V AC (to neutral), including the two pins of the large smoothing capacitor.  The large smoothing capacitor measures 6V DC only.  What might be the problems.  I am realy stuck and frustrated.

Try measure the input and output of the bridge rectifier. It should have 220 vac at the input and about 300vdc at the output. If it does not has output then replace the bridge rectifier.


Also how do one test a 3-pin relay and a package bridged rectifier.

Sorry never come across a 3 pin relay before but i do come across 4 pins and above relay. Since i never come across 3 pin relays i can’t show you how to test it. As for the bridge rectifier set your meter to x 10 k ohm  and measure each diode in the rectifier and it should show only one reading and if you got two readings then it is consider shorted. Do this test on each of the diodes inside the bridge rectifier. Test + to AC1, + to AC2 and then – to AC1 and – to AC2. AC1 and AC2 is the ac input pin while the “+” and “-” is the output pins. Hope this helps!






Hi David,

Wanted to give you an update on two monitors i have been working on that you have helped me with via email and also to ask you about another monitor.

First, i was working on two monitors and i have fixed one of the two.  I could not fix the Westinghouse L2046NV but i have not given up on it yet and i think it is actually the BIT3713 device that is bad.  But i am still working on it.  I will keep you udpated.

Thanks in advance.

The monitor i did fix was an old Viewsonic 15 inch monitor and the inverter board was bad.  I troubleshooted the inverter board, found a bad device, replaced it and now it works.  I plan on giving this monitor to a friends little girl for her birthday.  Thanks.

Congrat on your success and keep up the good work!

I am now working on another monitor and this one i have NO CLUE as to what the problem is.  I was hoping you could provide some insight.
Monitor:  Viewsonic VP150m
The unit does power on but the image is kinda “fuzzy” or “hazy”.  If i let it stay on for a few hours some of the “fuzziness” goes away but not all.  I am not sure what the problem is.  I think the lamps and inverter are ok since the image appears on the screen but i am not sure if this is a good assumption or not.  I have visually looked at the boards and all look ok.  Just not sure what to do.  Normally the monitor i work on are “dead” so its easier to pinpoint the problem and then focuson on a specific area.  But this time i am not sure what to focus on since the monitor does work but the picture is just kinda “fuzzy”.  Do you have any ideas on what to try?  Anything at all would be appreciated.

I have come across many lcd monitors with this kind of problem. If you found that all the output voltages are good then lcd panel is the biggest culprit.

If you have other question please do email me again.





Hi Silvio,

Hello Jestine, my Best regards to you my friend… I hope your business is going better and better evry single day…


i have a question for you, am having hard time trying to find some information and maybe you know or have heard about it.

The four IC (transistors) the drive the step up transformers in the inverter board for a Dell 1707FPVt with part numbers U402 BE5Y46, U402 BE513A (two of these) and U402 BE513U i would like to get some pin out configuration or datasheet. i google it, went to archive datasheet and nothing… i don’t see to find any info from these “little puppies”

if you have something please let me know or another componet that can be compatible, i would really appreciate it… thanks my friend and have a great day

Sorry i could not find that data too from the internet. I guess the manufacturer did not release the information to the public. Since i could not get any data i can’t recommend any part number for you.





Hello sir,
I am very glad for the news letter received from you on electronic repairing because am also a computer engineer by profession with little of electronic knowledge am working on sharp model TVafter troubleshooting i discovered that  the filament tube light did not come up and the TV is given out sound but no display and the line transformer is boosting i also used  another working   CRT but the problem persist.I want you to teach me how to test line transformer with the aid of DIGITAL MULTIMETER because i dont know how to used ANALOG METER. Thank you i will order for your book as soon as i get means, bye for now.


Hi Agboola,
Try visit this website:

Best regards,




From Santhosh,

Does all SMPS sense the load and give output according to the load?

Depends on the smps design. Most smps will sense the load

Does mobile chargers sense load and give

Depends on design as not all mobile charge use smps. Some still use linear transformer.

Does commercially available SMPS boards for projects sense
load and give output?

Depends on the design. You have to open up to see if the smps have optoisolator ic or not. If yes then it can sense the load. However some design use the secondary winding in primary side to sense the load.





hi justineyong good morning.

        Now a huge amount of smd components is used in electronics product like mobile phone .Defective smd components is to be removed from and resoldered  to the pcb is not as easy as conventional components.There are many smd rework station is in the market but the right desolder and solder is a question . So what technic should take to perform this job



 thanking you


Hi Suresh,

The best is still use the rework station which is fast and easy to solder and resolder.





Hi,sir jestine

                Asking only how can got the copy of a book,by HOMER L.DAVIDSON trouble shooting and repairing solid staes tv,because in my country they have no available a copy of this text book,thnks nilo..


Hi Nilo,

You can buy it from





I have a sony model #kv-24fs100,it has low voltage but won’t power up.


Hi Richard,

Try isolate the problem using the method in the link:

and if the problem still persist then you have to check all components in the primary side and if possible replace the power ic and retest again.







Thank you for sending me this month newsletter regarding repair-microcontroller circuit, I called it in my own as system control IC.Although I have a little idea on how it works,  still I’m grateful enough for your additional infos about it especially the circuit function and operation including of course the trouble shooting.It is really very helpful.

You ask me before what about my passion?  Well,  still planning for it when I quit working here in Saudi Arabia. As I said, I want to open my own electronic repair shop when I came home to my place in  the Philippines.


Thank you very much.





  Hi Mr. Yong:

I am thanked by the bulletins that you send me.
I read today the information about the microcontroller, EEPROM, cristal circuit, reset signal of the microcontroller and other
troubleshooting of the monitors.
Now I know more tests to solve most monitors troubleshooting.
Excuse me I don’t speak english very well .

Have a nice day

Miguel Acuña Fallas




Hi Jestine!!

Pls help my tv set

I found there is a resistor which connected in parallel across with the degaussing coil and in series with the thermistor (ptc) burnt,the first color still can be seen that is yellow color ,the second .third and fourth color are burnt.
Any body knows the value of the burnt resistor?

Is 4Xohm.4XXohm,or 4XXXohm…?

Best regard



Hi Yong,

From my monitor repair experience the value usually in the hundred ohms range so try 470 ohm and see how it goes.





hi, jestine thanks for ur support i just got the job done by the help of ur ebook  there was a diode 4007 short on the back side of the verticle ic n when i change the diode the tv was working fine so thanks again waiting for ur next article next month.





From Bailing,

Thank you for this month newsletter and posting in your blog about my order with the BIC.

No problem but so far not much feedback from the member.

About the monitor, I haven’t managed to find the supply pin of the microcontroller, but I do find 1 dry joint in the eeprom and resoldering 6 pins of the microcontroller ( the solder is too thin ). And also found some components are bending almost touching other components, so I put them straight. I also noticed that the ground cable screwed into flyback body ( through the big heatsink around the flyback already had a crack, do you think this will matter? Please see the attached photo.

As long as the wire touches the heatsink (cold ground) it should be okay

After reassembling the unit and power it up again, the display has only one horizontal bright line ( see the attachment photo, it was somewhat inclined to right side as before ) and I cannot test the display function at all now whether it could cycle through all the functions. Why do you think this could happen? Could it be that the vertical IC had broken?

Check the supply voltage first and possible dry joints. It could also be the IC have problem.

If I keep powering the monitor on ( for voltage testing for example ), could the bright horizontal line cause the picture tube to go bad?

Yes, please lower down the brightness or the screen control in the flyback so that it will not leave a burnt mark at the screen.

How do you see all the phenomena above, is it worse than the previous condition or maybe you could see the problem more clearly?

I have seen many old monitors, one after another problem appear the moment you repair the monitor. Just make sure all the voltages are correct and the microcontroller have the necessary signals and also make sure no dry joints in the board. Try knock it using the handle of the screw driver.

Congratulations for breaking the 60,000 visitors. All the best to you!

You are welcome and thanks for the support!





Hi Behzad,


thank so much of all reportes and guides so far but let me tell you what are problem in this country as electronics repairer:

1-  all brands  like  LG  SONY  TOSHIBA   SAMSUNG …..ETC they have thier own  service center and for one year they give free repair to all customers

after one year they repair but you have to pay ofcourse after 3-4 years they do not accept

your set and says that it is out of range and is not repair able and is old model but still we have problem

they do not sale the main parts( microcontorol ic for example)out of repair center and  i can not find in shopes  to buy from .  out side the country is coastly more

2- no schematices at all  because everything is monopol of the factory even services

3- the coast to buy a shop is very expensive in side the town out side the town no costomer

4- to rent a shop also due to infaltion in this country is higher than income?

That’s the same problem we are facing here but to those who can source parts, they will be making lots of profit from it. Have you try check your parts from this link:





From Reynaldo,

I am working on a 17″ AOC monitor unit Model no. 7En the unit came in with no
power right away I check the HOT (C5521Z) and found out that its shorted so before replacing it I have check Horizontal circuit and the sorounding of the HOT and I have also check the primary side and the secondary side specially the diodes all check and ok I grab my ECG book try to check it if there is a replacement no luck not listed so I went to the NTE semiconductior cross reference site to look for replacement again no luck so what I did I went through the circuit again and look at the collector and emitter side of the HOT and found out that there is a diode connected and diode is ok so judging from these I have concluded that the HOT is NPN w/o damper diode so I went out to buy the parts and found that only c5521 is available in our area so I decided why give it a try which I did the monitor was ok back to normal but it did not last long it only lasted around 3 – 4 days.

Have you check the internal cap at :

Try get C5411 for replacement. On for few minutes and then off and touch the HOT with your finger. If it cool then carry on to let the Monitor run longer. If it hot then it could be a wrong replacement or some other problem.

My question is can u recommend a replacement of the C5521Z and do u have any idea what site is also giving cross reference aside from NTE site

Try C5411, BU2525AF and BU4522AF. Sorry no idea on other website that provides cross reference.

My sister is not yet around they are still in vacation but she and his husband enjoy Malaysia very much.

Thanks for the info.

P.S. will you also include where can I buy some Semiconductor Cross reference aside from ECG which I already have the 18TH edition and the 1996 edition.

So far there is no websites selling any latest semiconductor cross reference. However if i found any new replacement book in local supplier i will post it into my blog and you can order from me.

Best regards,




Hi Jim,

Thanks for your April newsletter.It upgraded my knowledge about Micro controllers.Related to this,do you have the schematic of MC part no   TDA9370PS/N3/A/1665 ??

Sorry i do not have such information.

what is the difference between the capacitors 562J/1k & 562J/2k ?

Different in Volt. One is 1000 volt while the other is 2000volt.

can i replace a 562J/2k with 562J/1k ??

No you can’t but you can replace 562j/1k with the 2 k one.

what is the use of startup resistors in a circuit ??

To limit the high dc voltage to a lower value that is suitable for power ic to use.

If u don’t mind,can u please send me the original file of “A view of damai laut resort“(i saw it in u r blog).I love this picture and wanna keep it as my wallpaper. 🙂


God Bless..




Thanks Jestine,
The information you provided about the LCD monitor power supplies was very
helpful. The unit I’m having trouble with overheats the lamp transformer,
though. I think there may be a short in the lamp. But both lamps light up.
Would it be possible to to cross the lamp connectors to verify if the lamp
is the real defect? The cables won’t reach to the other connector position
so I would have to extend them. The wires seem to be insulated in Teflon or
some other slippery substance. I assume that is because of the high voltage
involved. Would regular wire work for a quick test or do I need to find
some of the heavy-duty stuff? Thanks again,



Hi Gene,
A regular wire for a fast test should be no problem.





Hello Jestine,
Thanks for keeping me on your mailing list.I find your articles extremly
interestng.I like to learn new things.
Best regards to you also,





Yap sir jestine I did the check the internal capacitor of the flyback using my digital meter fluke 189 and its ok again thanks sir I will try your advice sir
the C5411, BU2525AF and BU4522AF and I will also check your blog I have learned so many things by reading your blog.




Hi Jestine,


Today, I came across 1 Samsung Colour TV, in which when the power of the set is switch on, the power LED blinking on and off along with ‘tic’ ‘tac‘ sound (power relay clicks), and after few blinking (say 6 to 7 blinking) finally the TV turned on .


According to the owner, sometimes it stays blinking/clicks for a long time and the set cannot turned on.


Jestine, is these due to the leaking capacitors of on power section of the TV or its protection circuit had triggered the shutdown?


Any comment.


Thank you.




Hi Richard,

You have to open up the casing and see and most probably due to dry joints or cap with bad ESR value.





From Jehan,

I recently bought your e-book for testing electronic components.  (nice book)

Thanks for the support!


I have a Toshiba CF30E50 model 30″ television set.  This set is about 13 years old.  When I plug in the TV and press the power button, nothing happens (no picture, no sound) except for the power button led light flashes (I think it goes in standby mode).  I have already tried unplugging the set and replugging it to the voltage outlet.


Which components should I check first and in what order as I do not have the service manual.

Try this link to isolate the problem at


My guess would be The SMPT, filter capacitor, Horizontal Output Transistor, and flyback transformer for starters ?

Yes it could be those components that cause power blinks.

Secondly, what is the safe way to remove the flyback transformer and the anode wire that goes to the CRT ?

Discharge the anode voltage first using a screw driver tip and connect the tip to cold ground. Once you could hear some spark this indicates the high voltage already drained off.

Best regards,




Hi Sir Jestine, thank you very much for the another newsletter repair tips,it really help me a lot and thank you also for the repair tips about Laptop, i;ve already seen the trouble, it was the backligth,both end of backligth is darken.the inverter board is operating  i checked the output using a multi tester.again sir jestine thank you..god bless you and your family




Hi Jestine

Thanks  for your  the continuity of the newsletter I  have been receiving on a monthly basis. it has been extremely helpful and I  am forever grateful. However
I have been experiencing a problem recently which does not seem to go away. I am repairing a Panasonic Stereo, SAAK 220 which   continues to display F61 on the screen. I have exhausted all options which is known to cause such problems.

In this regard I solicit your professional advice in this matter, thank you for all of the courtesies you have extend to me, and await your speedy response.


Ezrol W


Hi Ezrol,

This message only could be read by those who are working in the service center. I guess you may need to send to them for repair.





From Kingsley,

Ok, I want to start my LCD monitor repair business.Can you help me>

Yes no problem.

How would I advertise?

Flyers to housing and business area, Inform friends and relatives, visit computer shops (most important), advertise in local newspaper, magazine and etc.

If I was to make a business plan,or if you made a business plan What would be in it?

Depends on your aim. What is your aim of starting a repair business? to get more profit, to support your existing customers and etc?

What equipment and tools do I need(this is very IMP-I will be getting money to do what I need,so please provide a great place with very good prices)

analog/digital meter
digital capacitance meter
blue ring tester and
blue esr meter

You may visit ebay dot com to get some used equipment and for the last two test equipment you may get from but currently their website been hacked and now trying to restore back.

.I need to know the set up,what is need,

repair bench
isolation transformer
solder gun
tools like plier, cutter, desoldering tools, smd rework station and etc.

What spares parts and cupacitor and other this I should have in my shop.Strictly LCD monitor repair for now.

Guess you have to keep some parts like fuses, transistor C5707 and different types of resistors and capacitors value. The best is if you have lots of Junk lcd monitor where you can salvage them. As time goes by you and many monitor comes in for repair you will know what to buy and keep in your spare parts compartment.









hello thanks for the good information in your website i have lg f700b crt monitor the problem is the colors are mixed together but when i turn the monitor off and then on it works good and the screen comes and is good besides if i turn it off for longer time and i turn it on again colors mixed together can you help me with that?


Hi Ahmad,

I suspect is the posistor fault. Check for dry joint and if possible direct replace the posistor and retest it again. Solder also the vertical ic section too.





Hello Mr. Jestine

I have the case or question,
If on power supply / equipment power source,
when check with multi-tester voltage is properly ( voltage found ).
But after conection with load voltage drop.
What any part ( capacitor, transistor or resistor ) usualy caused on the
or any others part ussualy caused this problem?

Thank yuo very much.




Hi Ari,
Normally cause by bad filter cap that have high ESR value. Sometimes if the load have some problem also could cause the power supply to shutdown.





From Abualgassim,

I would like to thank you very much for helping people in repairing electronics equipment.

You are welcome!

Really I have aproblem in dell lcd monetor model E172FPT, in invertor and power supply board, the  mosfet transistor 7n60b is short and also there is SMD IC which drive this transistor burned and I couldnot read its number, this smd ic has 14 pins. So,I would like to know the number of this IC , from your great experience or if you have circuit diagram for this model. I guess that it could be UC3842B , but iam not sure. thank you very much.


Since i do not have the schematic i can’t get the part number for you. It can’t be us3842 because uc 3842 has only 8 pins and not 14 pins.






From Russ,

Thanks so much for what you are doing. I know of no other site that
provides the practical electronic troubleshooting help that you provide.

You are welcome!

There are many sites with electronics information on repair but it mostly
revolves around theory and is not always helpful when you are actually
trying to fix a monitor or power supply. I think I have purchased most of
your guides that apply to my industry and they are all great and well worth
the money.

Thanks for the support!

I have a question on troubleshooting that I am not sure you
have covered but would be very helpful if you could provide some insights
into the subject.

No problem!

Lets say you are looking at a pcb of most anything. Monitor, power supply,
controller, etc. Using a DVM is there ever any general information that can
be learned from taking voltage measurements of any component. Can you ever
tell if there is a problem with a component by just measuring the voltage.

Yes if you know the circuit well. For example along the B+ line in some Monitor design there may be a fusible resistor (very low ohm resistor) along the same line. That means before and after the resistor there will be not much different in voltage measurement because the value is small. If one side have voltage and the other do not have then you can conclude the resistor have open circuit.

Without having any schematics. On a transistor should there most always be
a .7volt reading from base to emitter


Or if you measure from emitter to
collector should you always read a positive voltage and if it is not there
does that mean anything?

It depends on the circuit design. I suggest that you test on some working equipment and jot down the result for future reference.

What about a diode or zener diode. Can you ever
tell something without knowing having the schematics just by measuring
across the leads?

For diode you need to know the spec and zener diode you need a zener diode tester. Please visit this link:

Same with a cap. Is there ever a case where a capacitor
will have an AC or DC voltage on it that can lead you to suspect it might
have a problem?

You have to understand the circuit function. For example caps in the secondary side of power supply are mainly filter cap to remove ripple and cap in the amplifier circuit is for coupling purposes and etc. Different circuit need different technique to repair it. May i know what sort of equipment you are repairing?

Or maybe an absence of voltage might lead you to suspect a
problem. I think I know that the answer is no, but I am hoping that you
might have some experience with this kind of thing and might have some
general guidelines if there are some cases that it does apply. I ask
because sometimes I get stuck fixing something and I have no paper and no
idea what to do next. I just sit there looking at it and poke around with
my meter. Even with a Huntron and a good board it is still hard to tell
what exactly the problem is. Thanks very much for your help.

If you have other questions please do email me again.

Best regards,







  1. Allan

    November 30, 2009 at 4:31 am

    can you supply me with a schematic of a Kyoritsu 3111v insulation-resistance tester
    please Mr Jestine? As i opened the unit for maintainance, the red wire from the battery supply broke off from the PCB, and there are no physical signs of where it came from. Can you please help?

  2. Tojo

    January 27, 2010 at 9:46 am

    Hi jesting, i've also send this message but its very important so i resend it, i have ups pro600p that doesn't backup at power failure and i've just replace the battery but no result. what do i do?AT power failure beeping sound ring continuously such as the battery is empty or after testing, its full

  3. admin

    January 27, 2010 at 10:10 pm

    Hi Tojo,

    It could be the problem of a bad eeprom data.


  4. Tojo

    January 28, 2010 at 10:21 am

    Hi Jestine, about the problem of the UPS that doesnt backup, you say that it's a problem of eeprom but i think that it isn't. i can see no eeprom inside, the integrate circuit that i see are timer comparator and nand gates

  5. admin

    January 29, 2010 at 8:44 am

    HI Tojo,

    I came across a APC UPS before and after installed new batteries, it still won't work and the LED flashes. Once the eeprom been reprogrammed (smd 8 pins eeprom) it worked great. I forgot about the model that's why i suggest that you check for the eeprom.



    March 25, 2010 at 9:25 am

    Iam looking for circuit diagram for prolink monitor model PRO-1986.
    Please help,

  7. admin

    March 25, 2010 at 9:49 am

    HI Philippe,

    Sorry, i do not have this schematic diagram. You may try to find from this link:


  8. norma holmes martin

    January 22, 2011 at 7:37 pm

    hi sir, i have a 50" samsung plasma tv model pn50b450b1d vers sl04 that screen went black & cut off while viewing vcr tape, tv led went blinking & i could hear clicking. i tried turn-on w remote but same symptom. i unplugged it & on turn-on led on, blk screen, no sound except 4 what sounds like safety shutdown clicking & then stopped. i was e tech on gov contracts in & i used to repair tvs, stereos, etc. i suspected hot w damper prob. i bought this tv cash just 12 mos ago. would u know hot 4 this? i am assuming by pix & sound going together that damper is part of hot package trans. if u no of schematic that would b great. would appreciate any help.

  9. admin

    January 26, 2011 at 6:25 am

    HI Norma,

    Sorry i do not have the schematic. Is all the output voltages from the smps good and stable? If it is not stable it can cause many weird problems.



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