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Electronic Repair Questions/Answers & Testimonials- Part 33

By on May 5, 2009

Thank you very much for your help. I truly appreciate your absolute dedication and complete sincerity for wanting to help.

It’s very, very rare to come across people like you Jestine. You are obviously driven by  a great passion for electronics and not only that ,but also a passion for helping those who are stranded accompanied with lots of encouragement.

Thanx  again  Jestine.








Dear Jestine,


    Thanks for creating such a great e-book with all the information we need to fix our LCD monitors. I am completely satisfied with the information it contains and I know it would be of enourmous help now and in the future. Hope you are making more of this material in the future :).






Hi jest Hope that U fine as I`m good. I would like to take this oportunity & say thank U very much For the info I`m so greatfull to have known a person who is so generous as U are.
It is difficult to get such valueable info from people especialy in our field, it gives me great pleassure to say thank U & I`m very greatfull, U must know that I say this from the bottom of my heart as I highly appreciate your effort in giving us the proper knowledge of doing the job excelently. I`ve also told my Friends about U so unfortunately they dont have access to the net but we all happy to have such a great teacher as U on our side.

We would like to thank you very much for your kindness, keep it up.

Looking foward to our next mail.

Yours faithfuly
Bain Xolane Nyati.




I must complement you on your book Testing Electronic
Components for I learned a lot of things in it.






Hi Jestine ,

Today i have repair 1 set lcd monitor AOC model LM520i , the problem is power “ON” few second , the display black , no backlight ,. Then i change 1 pc condenser & board dry joint at inverter board . Thanks for your ebook , Thank you very much .






Hi Tani,


Here are your questions and answers:


Also how do I trace the fault source of an under voltage output from the secondary side? example: 12+V has only 11.9V output, what can cause this low voltage output,

The 11.9 volt is consider good because output power supply voltage have tolerance.

and how do I read the real DCV output from the secondary side of a power supply?, cause, I believe wiring color code are not always the same.

You need to schematic of the power supply because all output power supply produce different output voltage except the computer ATX power supplies that have standard output.


Sorry to ask you so many things Jestine your the only one I know who can easily help me. I am learning alot from your books but it will take me some time of testing and evaluation before I can really do it well.


More practical will only make you perfect. Keep up the good work!





Thank you Jestine!


I have learned many things since I first purchase the test electronic component pdf file. I have repaired a couple of keyboards and some other small electronics. Computer power supplies are easy to fix if the problem is visible if not then not worth it considering the amount of components and time it takes. Have a great weekend!






hie  Jestine Yong ,hope you had a good easter.

At my workshop I am confronted with malfunctioning DVDs,in most seems the sensor can no longer detect an inserted disc,it reads -NO DISC. How do l go about this.


Hi Ronald,

Thanks! As for the DVD try check the spinner motor as if is slow or open circuit will cause the no disc symptom.





Message: i need a contac to buy a maim board for parker electronics lcd tv lcd20sy3ba



Hi Trevor,

Sorry no information on that.  Have you try ?











Since i’m not in this field i can’t give you any expertise advice on this topic-sorry!





Hi Brian,

Here are your questions and answer:

Thanks for your contact number.

You are welcome!


What do you mean by Assembled kitset, what the different?

Assembled kitset means we have fixed the meter for you. Kitset means is not assemble yet.

And the blue ers meter can test those capacitor value?

Please visit this link:

or i need to get one of those digital cap meter instead?

Digital cap is meant for non polarity caps like ceramic and etc

 where can i get digital cap meter?

You can get it from pasar road or any electronic supplier shop in your area.


Another query of mine, I saw some of factory using power transfomer step down to 220v – 240v, and the ground cable from a pcb board connected to the device cover casing with a screw, will it be dangerous if we touch it the casing?

 it that harm us fro your point of view? as it is using 240v power spully for a machine, and the transfomer ground cable just connect the casing with a screw, how safe it is? It make me scare to touch those transformer.
Ground means earth and you can touch it. It is just like computer casing. However if you are not sure whether it is a ground or not then do not touch it.


This phenomenon also happen to a ABC shaver, I saw the ground cable just screw to any part of the shaver body. Is that really safe? I thought it will shock, as ground connecting to the power for circulation. am i right?

Try visit these links for more information about grounding:




Thanks for your time. Even you busy for your stuff but still take time to reply my email. really appreciate.

No problem.





Hi, Jestine,


Thanks for your reply.  To be more specic about my problem, I was testing the components in the rpm circuit as it is fully electronic. I tested one resistor which on colour code was 5.2K  it read only 3.5 K. But when I change it to a new one, and soldered it on the reading was still 3.5K I am curious as to mwhy it is so. / Hope you could shed some light on this.





Hi firdaus,

Normally when resistor have problem the value is either increase or open circuit and very rare i see resistor value drop. Could you confirm the resistor code?





Hi Jonathan,
Here are your questions and answers:


Thanks for your news letter,

You are welcome!

a while ago I asked you if you had any Idea or help you could give me regarding a 17″ LCD Monitor I have, only make and model number I can find on it are Model: L-171, Input 12V DC 4A, and the site name is, its in Immaculate condition and was working fine untill I accidently plugged my Toshiba laptop power supply into it which is 14 V DC, now when I plug the 12V supply to it all I get is a green neon at the monitor on and off but nothing else happens, I’ve looked at the board at the back but can see no trace of burnt components or no inline protector fuses which I could replace, any ideas justine would be greatly appreciated. Yours Faithfully Jonathon.

Connect back the original adapter and check all the voltages to the mainboard and inverter board. If you get good voltages then it could be the mainboard bad. If the voltages are low then start checking on the pc side where the dc jack area is located. If you have other questions please do email me again.





HI Jestine,

I`m doing both but more to monitor repairing…
Hope you can help me to make me more understand of this b+ circuits..



Hi Wan,

Modern Monitor B+ circuit consists of only two types ie boost circuit (boost the dc voltage to supply to flyback ) and buck circuit (buck down the dc voltage for the flyback). About 90% of CRT monitor in the market are using the boost circuit and it consists of n-channel fet, B+ coil, a diode and a capacitor while the buck circuit normally use the p-channel fet, b+ coil, diode and a capacitor. For more information on how both circuit work you need to click on the below link:

Best Regards,




Hi Jestine….
Bantu saya…apa sebab2 nya yg berlaku begitu…thks Isa


Hi Musa,

Kemungkinan kerosakan mainboard. Samsung model biasanay ada masalah ini.





Hi Jestine,


I am suprised myself. The colour code is  reen,brown, red and silver.The old resistor when it was taken out from the circuit also measured correctly on the multimeter. How ever when it is soldered on the circuit  and measure the ohms it drops in value. Other resistors  even measure withot taken out measure correctly. I further discharge the capacitors just as precaution.


I noticed there were some zener diodes connected in the circuit. Could they be affecting the readings?




Hi Firdaus,

To check resistor one has to remove one leg from the board for accuracy. Checking on board will usually cause the value to drop due to parallel circuit.





hi there,

i thankfull to receive your newsletter every month.

it’s help me to understand electronic circuit implement more detail.

hope you keep this great job to share your knowledge to everyone else.

thanks alot.





Hi Jestine,

Thank you very much for sending me about the microcontroller troubleshooting guide it help me a lot in dealing with microcontroller troubles and problems.


Best regard & more power





Hello Jestine Young

if I have problems or finding it difficult in repairing any electronics items, should I please consult you for solutions? If the answer is Yes, should you please help me out with this problem.

Have a faulty monitor:

  • ViewSonic G655, Model # VCDTS21468-1A, S/N # IP93500056. The power is ok but no display. Opened the cover and found two small blown electrolytic caps (description: G-LUXON, SM105 degreeC / 9065 (M), 10microFarad/50V), plus 1/2W resistor burned. What is the cause? Is there some other components that may also go faulty that need to be checked? What are the repair steps I can take to repair the item?

thanks for your time



Hi Bob,

May i now where were the faulty components located? In power supply side or other circuit? If you found the bad components the best is to check all corresponding components before you turn the equipment on again.





Hi Wael,
Here are your questions and answers :

hi   mr  are  you   .

I’m fine thank you.

have  youj  heard  about  the  new  piezo  inverter  for lcd  monitors  they  say  in the internet  that it can be used as  a general replacement for all lcd  lmonitors  ccfls  lamps  no matter what the shape  or the voltage  requirment  of the lamp the inverter  can power the lamp  effectively …

I only heard of inverter board that suit most lcd monitors.

.but  some  websites  say that sooner all lcd  will  be  using  leds  as  a source  of light instead of the ccfl ..

Yes that’s true but it will take couple of years more before it will reach to our repair bench.

.but  according to what  i know  as  a technicians  that chineese  manufactrures  does not  care about the  fact  that  a led  consumes   less power than ccfl  as i know as long as the ccfl  is cheaper they will continue  making  lcd panels based on ccfl  as back light  because there is no  significant  difference between the pictue  quality of  monitor  that uses  ccfl and that one that uses led …actually  if they  will change  soon  to led this means more problems to technicians cause  led have no inverter  just small  unrepairable  dc to dc boost  converter that powers the led  bars that replaeces  the  ccfl   …and specially with this good new that there is  a piezo inverter that  can replace all inverters  now if you cant repair the inverter board you just  plug  in  piezo inverter  to complate the job …with no inverter  there  is nothing  left to us to repair  but the switch mode power supply

You got a very good info but need not worry as there will sure a solution for all electronic problem. For your information, in this coming June i will be going to China Shenzhen to visit the electronic hub and try to get as much information as possible. If the visit is fruitful then i may go there more often to source for information, parts and etc.

Best regards,




jesting,I’m so glad to meet with someone like you,you are empowering me really,however could you jenting teach me how to repair tv(ray cathode tube type)show me how tv works ie voltages pathways,resistance infect i only know to repaire power supply beyond that stage i am having a problem and poeple need their tv’s and tey trust me.teach te stages of tv I dont know whether what I ask is clear or not.please help poeple bring their tv’s to me saying I know how to repair,and I telling them that I dont too much so I také tv’s to a certain guy to help me with repairs but thi is costing me,my I hope you will understand my problem and offer me this assistance.
GOD bless u


Hi Monwabisi,

Try visit this link as it has lots of tv repair information
I used to read from this website too.





my computer had a start up problem so i have changed my power supply. but once i changed my power supply, it still cant be on. there is a start/ power going in and the procesor fan turning but less than one sec, the supply gone.(turned off buy itself) please advice me wat to do. thank you.


Hi Puru,

It could be eitherthe power supply itself have problem or there is something shorted in the mainboard that had caused the power supply to stop working.





Hi Jestine


I really wanna appreciate for sending me those news-repair, it really helps me a lot. Now i am able to distinguish between microcontrollers and microprocessors. As you have told me that being a student at a university or a college doesn’t mean you know everything.


Thanks Jestine, I am looking forward to read more from you.






Hi Sir Jestine Yong..


Jika tuan masih ingat lagi, saya adalah salah seorang customer yang membeli ebook tuan tempoh hari.

Disini saya ada beberapa soalan berkaitan ebook yang saya tidak fahami.

Saya harap tuan dapat membantu dan membimbing saya dalam hal ini.


Soalannya :


1. Saya masih belum faham apakah yang di maksudkan dengan “hot ground” dan “cold ground” ?


2. Bagaimanakah saya nk kenal pasti yang mana satu “hot ground” dan yang mana satu “cold ground” ini di atas sesuatu litar elektronik?


Segala bantuan dan pertolongan tuan saya dahului dengan berbanyak-banyak terima kasih.



Mr. J


Hi Mr J,

Hot ground adalah ground di bahagian primary side of power supply (SMPS). Sekiranya anda jumpa satu capacitor besar (nilai biasanya 220 uf 400 v) kat bahagian power, kaki negative capacitor besar itu adalah hot ground. Untuk cold ground adalah ground dari plug building kita ataupun ground kat bahagian secondary of power supply.





HI Amos,

Here are your questions and answer:

 Good night to you and your family.

Good night!

Thanks a lot for your help regarding the vcc pin of the power ic. I just confirmed it tonight by testing it. It reads 15.1..Volts according to your Book (Lcd monitor repair). Now i know where the vcc pin locates. Thanks so much.

You are welcome!

Now I’ll continue with my practical on testing voltage on the secondary side since on the primary side is OK.

And My next question is, If there’s no voltage present on the vcc pin of the power ic, which suspect components will I check along that circuit area?

It could be line resistor open circuit, shorted power ic or even shorted corresponding components.





Hi Bailing,


Here are your questions and answers:

Sorry for the late reply.

No problem.

About the vertical IC of this monitor LA7838, I’ve checked all the supply pins. According to Acrisoft I should check pin 1 which I got 10.7V, pin 8&13  I got about the same 21.9V. So the supply voltage is indeed within range, but I wonder why I got a horizontal line in the center of the display?

Have you check the resistance of the vertical yoke coil? An open yoke coil could cause one horizontal line problem. Does acrisoft provides support too. Did you get their monitor repair manual? How’s the information in it? Have you replace the Vertical IC?

As for the CPU, I still have difficulty in searching for the supply pin because there is no Regulator IC ( 7805 ) on the board, but at least I checked the voltage of the electrolyte cap in the vicinity of the CPU, and as expected I got stable 5.7V. I also checked the Xtal with the scope and got the sinus wave.

If the crystal go the sinewave most probably there is a stable supply to the Microcontroller.

As you say earlier that this monitor might have bad eeprom, but I keep the monitor for sometime to do some checking and measurement. Though I can’t repair it, I wish I could have learned something from it.

Yes you should do your own testing.

Every time I open the case of a monitor and look around the deflection yoke of pc tube, I always see some cable bound around the neck.  What if I turn on the monitor with the cable tie cut open? That is the black cable is not around the neck to stretch that cable so as to do the troubleshooting with the mainboard easier. Would this affect the convergence or magnetic field? Please see the attached photo.

If i’m not mistaken the cable is for controlling the horizontal centering and yes you can cut it and see the different

How do you manage to see the display while taking some measurements?  Do you use  a mirror beneath the table?

Sometimes yes but most of the time i just place my head lower in order to see the display.





HI Terrance,
Here are your questions and answers:


I have got a problem with my TV .When I was physically checking it I
found that the fuse has blown;so I replaced it and then the same thing
happened (blown).

You need to check the bridge rectifier and all the semiconductors in the primary power side.

I used a multimeter set on diode(with sound) test and tested several
parts but I met a three leg IC which suspect it to be faulty.What
might be the problem?

What is the part number of the ic?

How to test a voltage regulator.

You need to power on the tv in order to check the voltage regulator. Assuming you have the power check the input and output pin of the voltage regulator. If the voltage regulator spec is 15 volt then your probe should measured 15 volt at the output pin and the input pin should have higher than 15 volt-maybe 20 over volt.




Hi boby,

Here are your questions and answer:

Firstly would like to inform you that while waiting to save up money to buy the E-book that I am trying to buy,  I would at times consult you for some advice regarding electronics item repairs.


1).  Anyhow, I am bit confused or finding it hard to test any type of transistor, both that have labels and without labels as base, emitter,     collector or drain, source and gate.


should you please advice me on how to test the transistors especially those without labels and identify whether bad or good  using analog and digital meters.

I wish to help but testing transistors (fet, bipolar, hot, darlington and etc) are big subject thus i have compiled it into an ebook.


2). When measuring voltages on the main power capacitor, our power rating is 240V AC/ 60 Hertz, therefore will I put positive probe on positive terminal and negative probe on negative terminal, and when using digital meter, will I switch to DC or AC sign for measuring? Please advice.

If you are checking on the electrolytic filter capacitor in power supply  yes you should select DC and positive to positive pin and negative to negative pin of capacitor.


3). When measuring voltage on HOT and power transistor, will I switch to AC or DC sign on the meter? And also positive probe to which and negative probe to which. (both for analog and digital).

Normally technician check on the B+ voltage to the HOT and you should select DC where positive to B+ pin and nnegative to cold ground.


4). lastly, no power in the LCD monitor. Description: Vusys lcd monitor, model # HD 15A, S/N 512NML5010037, 12VDC / 3A maximum. Tested power switch Ok, please advice me what is the fault?


If no power i guess you have to check the fuse, bridge rectifier and etc. If possible check all the components in power side and if all tested ok then direct replace the power ic and retest it again. Check also the secondary side diode as this could cause no power symptom too.





Hi Jestine,

I recently purchase your LCD repair package and starting to learn to repair LCD monitors. I have an Acer 19″ Monitor that wont stay on. The screen would only be on for 2 seconds or so then go off( The screen display perfectly). Here are the steps taken so far.

1. After I opened the LCD screen, I found that the top back lights were bad.

2. I replaced the back lights.

3. The LCD stays on now for good but I have a new problem.

4. There is an area that won’t display anything on the screen. This area is black initially and then turn to white later. Please see attached picture.

I made sure all the connections are tight and that the TCPs are not ripped.

Please help.

Thank you,
Tom N


Hi Tom,

Thanks for the support on my ebook. From your description i guess the problem is in the lcd panel and there  is no way we can solve this kind of problem. Probably could it be when replacing the backlight had caused a tear in the tcp package? Please recheck the area again especially on the top part.





Hi Jestine

Your instructions are very useful and wonderful. I have two questions. First I did as told about dell E173fpb monitor and changed those four transistors (C5707) and it worked fine in three weeks then back again in same fault namely power on button blinking but display is black. Is there some help or it is useless.

Kind Regards



HI Moris,
Check for dry joints in high voltage transformer pins as it could kill the new C5707 transistors again. t





Hi Marc,

I have an PCB board, that i wish to reverse engineer. The components on the board are diodes, capacitors, resistors, and 1 crystal. May i ask what does a Crystal do?

Crystal is use to generate a precise stable radio frequencies

Well I want to test them to purchase the EXACT ones for production. How would i go about this process?

You need to power ” on” the equipment and test it with scope or with a frequency counter. You can also test it with a crystal oscillator tester.

Do you have a service where you can test them for me? Because i know your company have the proper tool to accomplish this task. Please its no more than 15 components. Thank You

May i know where are you from? By the way crystal oscillator rarely have problem.




Hi Jestine,

Thanks so much.

Can you show me how to test for voltage from the on/off or 12 volts switch to the inverter ic please?

(something like placing of meter probes to cold ground and meter probe to vcc pin of inverter ic etc…..)

Thank you and hope to hear back from you

Best regards,

Amos Kaili


Hi Amos,
Yes that’s right place the negative probe to cold ground and the red probe to vcc of the inverter ic. First you need to get the datasheet of the inverter ic. Once you have found the vcc oin you can trace it backward to see where the source from. With few experience and writing down the journey will make you become easier to test on any voltage point for measurement purposes.





Your Name: sankarakuthalam
Message: your articles all are fine and very useful to me




Hi Jestine,
Good afternoon.
Thanks for your guidance through the practical voltage test. Now I understand little when you mention something about troubleshooting (tracing backwards) – to do with testing of components and finding the fault.
Million of thanks to you. you are so helpful and kind.
If you have any other valuable information or report on critical voltage test, you can send one for me to have alook at it.
Thanks once again.
Best regards,
amos kaili




Thanks Justine…..   Mission accomplished   I am already very pleased with my purchase   Bill




hello mr yong.

how can i replace cpu ic in electronic device ? ( for example: cell phone)

do i need specially tools ?

please help me.

thank you.


Hi Saeed,
If it is a smd ic then you need a rework station.






Dear Jestine,

About the original  vertical IC, what do you think is the problem. Was it because the IC broke down under full load? After desoldering it off the board, I had compared all the pins resistance to ground pin ( 11 ) and they have exact resistance with the good one.

Thanks again,


Hi Bailing,
Since deep inside the ic have lots of circuit and components by comparing resistance does not help much. I have many personal experience where comparing resistance were okay but fail when power on.





Thanks Justine for your good information to me, I appreciate, i would like to know how you can mesure / test an IC


Hi Egbert,

You are welcome and to test ic one need a scope to test the input and output pin but first you must know the spec and you can find the datasheet from the internet. To some technician they use a tester call as huntron to compare its signature. please visit for more information





Hi Jestine,

Good morning to you and family.

Thanks a lot for confirming my questions. I already traced the vcc pin of inverter ic. I placed the black probe at the cold ground and the positive probe at the vcc pin of inverter ic and it reads 12 volts. Its very interesting reading your Ebook. It helps alot.


Is there any other critical voltage test to be perform apart from Bridge rectifier(Ac volts), filter capacitor(dc volts),vcc pin of power ic, secondary voltage test(cathode of diodes), on/off switch to main board and voltage –  vcc pin of inverter ic?


Thanks and hear back from you soon.


 Amos Kaili


Hi Amos,

Actually there are only few critical testing points in any equipment. Once you found that one of the testing point is not according to what you are expecting then you know where you should begin to start troubleshooting. Assuming if you did not get 12 volt from the inverter ic and there is supply of 12 volts from the power supply, with these information you know that you have to trace backward from the inverter vcc pin and see where the voltage has lost. This are just one of the thing that had made the troubleshooting so fun and exciting!





Hie Jestine

I stumbled across your name and its big reputation from an electronic technician friend of mine.  We thank God for the blessings of people like you. I believe I am going to greatly benefit from an engineer of such a big repute. May God richly bless your future.





Hi Bailing,

Here are your questions and answers:


Today I spend quite some time checking the vertical section. The vertical yoke resistance is  7 ohms,  it has 3  led bars  when checked  by the blue ring tester, I thought this should be ok.

Yes the winding is okay.

I also checked  most  of the diodes, transistors and optopcoupler on the mainboard, all were good. So I decide to change the vertical IC and then power it on, now the display is back to the condition where the customer gave it to me. Thank God, that I don’t make it worse!

Yes sometimes in troubleshooting out of sudden additional problem could appear especially on older Monitor.

About the Acrisoft book, I don’t think they give support to the their customer, because they don’t even give the support e-mail. I like the way they write the book ( most of them telling about analyzing the study cases of typical circuit in each monitor section and of course the tips in troubleshooting ), but I don’t like the writing ( language ) because the writer mother language isn’t english and I don’t get what some of the explanation means and it seems that they didn’t even do any proofreading before releasing the e-book. And as you had said to me, the e-book is not able to be printed, so I had to use capture software to make it printed. Still the worst, 40% of the schematic diagram they provide is hardly clear to see ( blurred and too small ), and last but not least all the schematic they analyze are old samsung monitors.

Thanks for the complete review of the ebook-appreciate that.

Last time when my sister came from Taiwan, I asked her to bring some parts. Here I attached the photo of N-Ch K3264 Mosfet. I wonder why the manufacturer isolate the source pin? Have you seen any type of Mosfet it source pin being isolated like this? What is the purpose of doing this way?

That small bead was use to keep the fet from mild spike/interference. I have seen many in HOT and also in the power FET especially in the ACER model.





hi i have a question i am tring to fix my screen it died but i cant buy your guide i have little to no money but i need my screen for school its a gateway and it seams one of the compacitores is bad but none of them look bad on the out side but the screen comes on then turns off after displaying the gateway logo for maybe 1 sec. thats it if you could please help a poor man out it would be great thanks



The problem could be in the inverter board and a bad backlight. make sure the inverter ic is receiving supply voltage even though the display already shutdown.





I have a trouble when repairing printer HP F380.
There’s a dioda in mainboard. there’s a code “S4”
Then I looking at, I found :






npn vhf 15V 0.1A






low fwd V schottky 40V 0.1A






low fwd V schottky 40V 0.1A

but I can find schottky in my region.
May I change with a different kind of dioda?
what kind of dioda may I used?



Hi Andre,

Yes you can try another number but make sure the spec is equal or higher than the Original one. The best is to use back schottky diode. Assuming if you can’t find the smd diode then the only choice you have is to use a bigger diode like the UF4007 as replacement. You have to think of a way to fit it in. Hope this helps!





I do not have a Problem with the crystal. I wish to test it to fine the exact part to purhase about 100. The Part Number of the 2 crystals Mark:
XTAL1 – 6,00C6X
XTAL2 – 20,0C71

Do they look familiar? Are you able to read off the Part number? Please let me know Thank You


Hi Marc,

If i’m not mistaken the XTAL1 is 6 MEGAHERTZ and Xtal2 is 20 Megahertz.





Hi Boby,

Here are your questions and answers :

1).   When this components at the flyback area blew up, bit frightened to power up the monitor and check the voltage on the blyback transformer, so what other steps can I take, or how can I check the voltage on the flyback transformer?

To check voltage of flyback you need to power on the set. If you can’t power on the only way is to test all the suspected components like HOT, b+ fet and etc. Once you found the components then you can switch on again.

2).  Tested a FET, (a transistor at the output of a PC power supply), on all its terminal and all gave peeping sound so does this mean that it is bad?

If all terminal have sound (have sound means the resistance is less than 200 ohm) then the fet is shorted.





Hej Jestine
Thank you for posting the articles about microcontroller,these web are very very good,thank you and the web about electronic and technology are more useful for me.Thank you.




Hi Annie,

Here are your questions and answer:

good day! i have a computer monitor which only display a horizontal line in the center or at times will just display the lower half of the screen. if i will bend the monitor forward and see to it that the board’s plastic spacer will not a touch the table there are times that it will display full. i already re solder the IC’s in the board and the socket of vertical wire on the board that is connected to crt.(the 4 wires .. brown and yellow for vertical which is smaller than the blue and red of the horizntal )….


And i even tried to return it to the casing its still same.. you need to bang the casing  many times before it will fully….


what is the problem?

what is the loosen component on this?

 how will i solve this?



Try gently knock the vertical section area with the plastic handle of your screw driver to see if there is any effect on the display. I had came across if not dry joints problem then most probably is the hairline crack in the circuit line. You need a good magnifier glass to find such crack! Make sure also the vertical output IC is receiving a good supply voltage.






Hi Dennis,
Here are your questions and answers:

How are u hope u are fine as i am here,anyway thx for ur free April reports and the article is very educative

I’m fine thank you.

but i wonder how it can help me on my field b’cos i’m an auto electrician and as i went through the questions,answers and testimonials is all about fixing of tv’s, lcd’s, monitors i want to know from u is the application same to that of car electronics repairs or is there any way u can help me acquire some little knowledge on how to test and repairing of car electronics especially the electronics control units (ECU) etc.b’cos the cars manufactured now are full of electronics hoping to hear from u soon thx with
warm regards,

Actually all electronics are the same is just that how the designers form it in many different type of circuits. If you wanted to be good in the auto electronics repair then you have to get many different type of car electronics schematic and analyze it. It still has to come back the basic of how electronic components work and how to accurately test them.

In other words if i’m interested in TV repair then i will go full swing in getting only information about tv repair and so on. From what i know it is a bit hard to get information in auto electronics repair because this is a very niche field.

Best regards,
Jestine Yong




I have an electronics question, I have some boards with a J220 FET that receives 18 volts on the gate, the defective boards are receiveing 24 volts on the gate, there is a resistor in line that takes the 24volts in and drops it to 18 volts then it is fed to the gate. The resistor does test good on the defective boards but yet it does not have a voltage drop. Any ideas? I can fax you a hand drawing if that would help. Please respond with your ideas on this matter.


In your case you need to check the components corresponding to the drain and source pin of the FET. It could be an open current sense resistor and etc.





Hi doctor j.yong,a 21″ tv sumsang is showing green picture only,sound ok.what could be the problem?


Hi Frank,
Compare the voltage or signal in the CRT board between the Red, Blue and the Green circuit. It could be dry joints and bad components in the green circuit at the crt board of the tv.



Hi Harun,

We obtain your information form web site. After visited your website we are
very interested include a LCD Monitor/LCD TV service center with our
current business. Please be inform you that now we are dealing computer
hardware items and some electronics items.

Good to hear about your business expansion.

I would like to request you pls. let me know which kind of support we may
got form you in order to setup a LCD Monitor/LCD TV service center in here
and we need what kinds of Equipment , Manual , Book … etc.

Support in term of electronic repair questions

we need what kinds of Equipment , Manual , Book … etc.

You need the LCD Monitor Repair ebook and these testing equipment:

Blue ESR meter

Blue Ring tester

Analog/digital meter

Oscilloscope and

Digital capacitance meter

Best Regards,


HI Vic,

Congrat on your new scope! As for books, i can’t suggest any books because i learn reading scope from experience. However if you search from you could see there is variety of scope topic but i do not know which one is more on the practical side unless you see the review in each book. I have one scope guide by Dr Arnold Banks but that books have lots of theory and do not have much real photos in it.



HI Saeed,


1) how much increased esr is symptom of defective capacitors? for example: normal esr for 100nf/400v capacitor is 15 ohm,should i replace a capacitor with the same value but 17 ohm esr?

If possible replace the cap with equal or lower than the original value. Please visit this link:


2) can i test primary winding of linear transformers with the blue esr meter?


If it has a major short between windings then you can test it however if it has partial short your blue esr meter can’t test it and only by using Blue Ring Tester you could test it out.



Hi Rilles,

Dear Mr. Jestine, I have problems with a Samsung SyncMaster 705S CRT monitor. The monitor came to me with no display, but the green power LED indicator is light normally (not blinking). The owner said that if he turn on the monitor, the display is rather dark and it needs a few minutes until the display shows picture. I don’t have HV probe so I can’t measure the voltage, but I’m sure there is no high voltage output from FBT because : 1. There is no “high-frequency” sounds from FBT and, 2. when I discharge the anode, nothings happened (I mean no sparks).

I’ve build a Dick Smith LOPT/FBT Tester project I’ve founded from internet and using it to test the primary winding of FBT and it’s OK. I also checked the HOT it’s fine. I’ve measured the capasitance of HV cap of FBT with Capasitance Meter to find out if there is a short or open internal capasitor, it’s measured about 2.6 nF. Using Ohm meter to test it, not shorted, so it’s OK too, right?

If it has display then the Flyback is generating high voltage. You can’t discharge the high voltage because once the monitor had been turn off the flyback itself will discharge it.

I’ve checked the output voltages from the SMPS and it seems everything is fine as well as the B+ voltage on the HOT. But suddendly, when I’m measuring the voltage from the Horizontal/Vertical Oscillator IC pins (IC401, TDA9113) I hear a high-frequency sound when the probe meter touch one of these pins (the one with the infinity symbol). After that, I found that there are no more output voltages from secondary of SMPS trafo as I mentioned above. Now the monitor only give me a continues “tic-tic” sound with duration about 200-400 ms from the SMPS trafo. The power indicator is now off. Am I doing mistakes?

I’ve no idea what’s wrong? I’ve downloaded the Repairing Guide (PDF format) from the internet and following the instructions, but currently I don’t have a scope yet so I can’t see the wave form from the measuring points. Please give me some advice, may be your experience in repairing CRT monitors you have ever found the same problem. I’m stuck now, so your help would be nice. Thank you. Regards, Rilles E. Prianto

It may have cause something shorted that had caused the tic tic sound. Use this method to isolate the fault:

Check all the semiconductor again like the HOT, b+ FET and etc.

Please let me know about your progress.





Thanks very much for the quick response, I did fix one of them by replacing a CY644 fet from a scrap board. One more question, have you seen or heard of any components that start with the prefix CY? I did a google search and found no information on this part. In the same location on these boards some have CY644/CY520,CY 648, I assume all of these have the same specs because they are all in the same location but I cannot find any information on these to order new ones.



HI David,

Sorry never heard of such board location starting with CY. For your information some manufacturers just do not want to follow standard marking of board system and this would make us as electronic repairer have difficulty in finding the spec of thecomponents.




Hi Ari,


Firstly I say thank you very much for yuors support.

No problem.


Mr. Jestine I need your advise :


1. How to check capability dioda zinner.

    when chceck with digital multi tester polarity Ok( not leakage ), and point value on

    multitester  0.420 V.  But after install on PCB power supply not function.

    Second step I change dioda zinner type 3.0B2 ( point value multitester on  0.625 V )

    and than assembly at PCB ( Result OK. Power supply out put propperly ).

    For referensi voltage in put in line 20VDC.

For your information i do not test zener diode with digital meter because a bad zener diode the digital meter could tell you it was okay and this could waste your precious time I use analog meter to test on zener diode and different zener voltages have different reading. All these testing method i had compiled it into my ebook Testing Electronic Components.


2. What meaning marking on dioda body like this  Type 3.0B2 ?

It is a 3 volt zener diode.


I am worry after install or change this type ( 3.0B2 ) , can’t protect power supply if over load.


If you replace with the original voltage then you sould not worry.





Hi sir Jestine i am very much interested in all technical repair especially in electronics and computer as of now sir i have my own repair shop at home but i still love reading your technical know-how expertize.helps feeding my mind and i realy appreciates your kindness sir Thanks a lot sir and God Bless you and your Family






can the EEPROM be repaired oe replaced


Hi Jerry,

You can replace but you can’t repair it if it is shorted or have problem. The replacement must have the same exact program in it. New eeprom usually blank and you need to put in the data using a programmer.





Hi Wan,



How are you,hope youre doing fine,

I’m fine thank you.

Your esr tester and ring tester helps me a lot and save me lots of time…

You have invested on a good testers

I just wondering to buy a dc power supply,i think this can help me more…

I need your advise on this,is it worth it to invest in this dc power supply?

It depends on your budget and your field of repair work. I do not use it all the time but when i need it then it will be very helpful.

Want kind of power supply should i choose?

analog type would be cheaper than the digital one.

Do you have a dc power supply to sold?


Sorry i do not sell dc power supply, i guess you get one from your local electronic supplier. If you want to buy then get a at least 30 vdc with 3 to 5 amp dc power supply. The 30 vdc can be vary from 0 to 30 vdc to serve on different type of circuits.





Your Name: clive Message: One of the things that would be useful on here would be a component recognition sheet . many components although colour coded are faded or burnt and the circuit beneath them also obscuring there function ? was it a cap or was it a resistor ?.. without the circuit diagram how do you tell sometimes with new components it’s not allways that easy ? especially with micro surface mounted components .. what are your views on this ? … Regards Clive uk


Hi Clive,

If i come across such problem i would check all the corresponding components. It could be cap, resistor or other electronic component problem. As for the recognition of the part number, if i can’t get other information, i will trial on error by using some higher spec of component. Hope this helps!




Hi Jestine,

I am looking for a way to fix a horizontal or vertical black line in an LCD monitor and come across your book that says how to fix it. Can you really fix a horizontal or vertical line in a LCD monitor? Or there is a way to fix problem in LCD driver board? From my research people are saying it was caused by a failed transistors in LCD driver board. Can it be fixed? I am working in a company that sells LCD TV and monitor and we have pallets of this and the company is selling it for a cheaper price and if its fixable then its a business for me and as well as for you.

I am based in USA by the way, time is sort of gold here compared to Malaysia so repairing is kind of loss ends. But if horizontal line in LCD monitor is fixable then its a worth it venture.

Please let me know if your book provides the how to or you sell another book that does it.




Hi Jackson,

Thanks for your email. If the problem is a permanent vertical and horizontal line then there is no way to fix it. A replacement of new lcd panel is the best solution. However if the vertical and horizontal line intermittent then there might be a good chance to solve it. Please click on this link for more information:



Hi Saulos,

Many thanks for the April, 09 newsletter on microcontrollers.I have taken note of the findings and advice.

You are welcome!

I am wondering if you have researched and written on loading/ spindle motor servo drive IC for DVD and hometheater players. I’ve encountered a few appliances with a problem of this IC whereby the loading motor does not receive any voltage from the ic whereas the sled motor is power allright.

For your information, since i don’t repair much on those equipment i can’t write or provide any expertise advice on that topic. However troubleshooting is just the same-that means if the loading motor does not receive the voltage from the IC and the IC have supply voltage then chances is high the ic may have problem. Sometimes you have to check on those corresponding components too.

Since this is a surface mount device and I don’t have tools to remove this ic and it is not found on Malawian market, it becomes hard to repair such appliances.

Those SMD ic the best is to use smd rework station and since your side do not have it will be a little difficult to remove them.



Hi Boby,


1). no power through LCD monitor: (power rating: 12Vdc). Tested switch OK. tested power connection to the main board ok (power coming through adapter). It has a small compact main board and the other board that has some sort of coils on it. I suspect it could be any of this two boards and the power indicator or LED. What is the possible cause and what I can do, & can you tell me how I can test the LED (3 terminals) to proof it faulty.

If the Mainboard have all the voltages and the led does not light- this prove that the mainboard have problem and you can test the LED using an analog meter set to x1 ohm.


2). Can you show me how I can test the power on the Flyback transformer when the power is on, and on which specific terminls. Sometimes the terminals are not indicated, or sometimes labeled with numbers, eg. 1,2,3,4,5,6,7,8,9,10.

Please visit this link:

you need to find out the B+ voltage from the smps to the flyback. Usually the B+ voltage for tv is about 110vdc.


3). Last time I told you something about two caps plus a 1/8 W resistor blown at the flyback area of a CRT monitor! I tested all the components at the flyback area and all seems to be ok. I then replaced the two caps with same volt rating but different cap values, and for the resistor, it was burnt that I just replaced with an 1/8W of a similar resistor. I powered on the monitor, the power came on for some time ( however no sign of display) and it blew up one of the capacitors again. Please any tips?

It could be cause by a shorted internal capacitor or even flyback. please visit this link again:


4). Please I need help to this CRT TV, CRT monitor problems:

  • power Ok, no display on screen

Make sure the B+ voltage is entering the flyback pin.

  • no power

You have to test out all the primary components and secondary diode too.

  • blurry screen

Flyback problem and you need to add in monitor blur buster

  • only white horizontal line showing on screen

Check the vertical section especially dry joints and missing supply voltage

  • some colors more vivid than others (one color dominating others on screen)

Check the color circuit in crt board and compare the voltages and it should be roughly the same.

  • picture or screen moving, not steady

Make sure all the voltages to all the IC’s are good.

  • picture or screen goes up to the top, botom, or side side, not displaying on full screen.

It may be eeprom ic problem.




HI Andrew,


I am a student at Laurentian University in Sudbury Ontario. Recently my roommate put this add up offering to pick up used computer parts, to our surprise we received several emails, and incidentally got alot of free stuff. The reason i write to you is that we have a bunch of monitors our biggest problem is a Gateway 900G that wont power up.I would like to have the ability to fix up myself. I really like the way you go into detail with your description in you book. However I am more a hands on person, knowing how to do something and actually doing it are 2 seperate things. Do you know of any courses such as yours that are offered a little closer to home (I reside in Canada, but i would also consider anything in the United States). Bottom line I really wanna learn about something like this, but it has to be in english and it has to be somewhat close to home in order to minimize expenses.

Thanks for your email. There is one in USA-please visit this website


Thanks for your help

Ohh and do any of your books cover troubleshooting for the Gateway 900G, we’ve taken it apart and found no burned capacitors as you described you the 17″ BenQ monitor….any insight would be greatly appreciated


For your information my ebook does not cover the gateway900g model because i can’t cover all models found in the market because there are just too many model. What i cover was about the principle. That means once you know the principle you will know the rest. May i know what is your lcd monitor problem?



dear sir,


             i m viral dhangar. one problem in lcd monitor.



problem:-   lcd  puroview monitor is very low briteness.. how i can repar this problem.



please give a answer sir.


Hi Viral,

It could be a bad backlight problem.




good day! i have a computer monitor which i can not adjust the H-SIZE (horizontal size) in the menu button. but all the other functions in the menu button are working properly except for the H-SIZE..


how will i solve this one? hope you help me.. thnx!




HI Annie,

It seems that it could be a modulation diode located next to flyback have shorted or it also can be a shorted pin cushion transistor too. The pincushion normally attach to a heatsink and located around the flyback area. Check also for dry joints in the flyback area.



Hi Jestine,


Thanks for your info,maybe i will go survey at some electronic shops around.


Yesterday i just repaird i unit monitor chasis 29”, the problem is the image become so blur,

After doing some check up,found that got some resistor value is not so accurate as it should be,

Then after replacing the resistor…the image is quite o.k,so i thought mught be the flyback ransformer…

After replacing with a good flyback…the image focus is so sharp…

I have read your artical about `Blur Buster`…its is so interesting,since i have this spoiled flyback i think i want to try thins method..

Where can i get this `Blur buster`,is it suitable with 29″ monitor?


Hopefully i can learn more with you…




HI Wan,

My company do sell the Blur buster and the price is RM35.00 each excluding transport. If your 29 inch tv flyback have two knobs then it can be modify into it. If it has 3 knobs then it would not help.




Your Name: desmond yap
Message: i wonder where i can get spare parts from a reliable source. ic and smt components.thanks for the time


HI Desmond,

Try check some of the electronic suppliers here




Hi  Wan,


It is good to hear that you sell the Blur Buster ,

Do you have the double anode cap to?(i read this one from your articel too)

Yes the blur buster comes with the double anode

Please refer to the attachment that i given for the picture of the  flyback model..

If the Blur Buster can fit with this kind of flyback i will definitely need to have the blur buster,

but i need your help in explaining more detail how to install this blur buster perfectly as this is my first time..

I have not tested on this monitor before but from your photo it seems that it can work. And no harm trying and let say it cannot work you can keep the MBB for future use. Once you got the MBB just email me and i will explain how you can connect it.


I also have several model of monitor chasis thas has this kind of problem from size 21 until 33,

Can i still use the same method,with the same model of Blur Buster..?

If the flyback have two knobs then chances is high it can use but test on the unit first.

If the flyback transformer itself has a crack on its body (also very blurry image),is it safe to use this kind of modification or

need to do something to cover the crack body first?or its is too risky to do this modification…

If the flyback have crack on its body then the flyback may not last but then again it depends on where is the crack located. It worth trying to install one and see the result.




Hi Waleed,


The problem is no display on the screen but raster is okay(I hear the high voltage sound) .

I measured the primary and secondary section voltage and result was :

1- I found 280 volts on filter capacitor.

2- The outputs on secondary section : 7v ,50v,80v,14v,and -14v .

    I found 6.73v, 52v,82v,14.58v,and not found -14v.

3- I measured IC 201(42 leg) on leg 11(vcc) =4.89v.

4- I tried search of data sheet for IC 201 but I failed .I don’t know any part number is right, these numbers as U625,DM024,M_LEJKL7-1004,and JFD38.what is the meaning of these numbers.

5- I touched leg 13 X-OUT,14 X-IN,19,21 on IC 201and I found leg 13 (2.4v),leg 14  (I hear weak sound)and the monitor shutdown immediately, leg 19 (4.17v),and leg 21 (2.0v).

6- I measured on IC 601 Vcc leg about 33v and drain leg about 278v, the number of IC written as ( DP904C ) .

7-I measured with only digital meter ,but I don’t have oscilloscope.    

8- what is the meaning of  F.B?

thank you for help me.


Look like the smps is okay because you got a good output voltages and the meaning of F.B is feedback and in the high voltage area Fb means flyback.


Your problem is have raster but no wording. You must check on the video pre amp ic with scope for the rgb signals. If you do not have scope then direct replace the ic and retest again. The IC is located at the CRT board. Could you read to me the part number of the IC’s found in CRT board?





Hi Ian,

Thank you, yes, I have read the interesting book you let me download.

You are welcome!

I wish I could say I have solved my problem with an Acer AL1714 monitor which
shuts down on start up. It has an external power supply and I have not
been able to find any electrolytics with “blown” tops or any other kind of
damaged components. The backlight seems to be working normally as the
screen was showing an image for a few seconds before shutting down. I
cannot find a fuse in line or elsewhere to check and I don’t know what to
do now. It seems such a shame to dump what was a perfectly good monitor
before the shut down. And no one is interested in repairing monitors now
saying, that it is cheaper to dump it an to buy another.

Shutdown could be due to few reasons like bad backlight, bad components in inverter board, dry joints and power supply output problems due to bad filter caps.

I suggest that you check for dry joints first before you compare the back light with a good working unit.Since now the economy was not that good more people opt to repair their equipment compare to buy a new unit but again it depends on which country. In my country customer still sending monitors for repair.

Have a good day!




HI Mario,

     I’ve read a lot of your articles regarding electronics repair and was indeed convinced that I could refresh again my knowledge in repairs, particularly in the new present era of LCD monitors-dealing mostly with SMD technology.

Hope you like the articles!

     I graduated from a 2 year Electronic Technician course last 1988 and started my way out dealing with repairs/servicing of car stereos,radio casettes, TV -black n white/color,basic design/assembly and installation of VHF/UHF antennas.
After a year dealing with repair job, went to college and graduated from a 3 year X-ray Technician course; but still continue doing repairs on my free time.

Nice to know about your background in electronics and yes do not give up as electronic repairing is fun and could make us money part time

     At present I ended up as factory worker in Japan, and at present my main concern is to really learn on troubleshooting LCD monitors. Actually, through your article I was able to troubleshoot 1 LCD monitor with no power symptom,by just changing 1 electrolytic capacitor! Junk LCD monitors here in Japan are cheap(but not all) and right now I’m having a hard time dealing with the rest of 4 LCD monitors.Can I ask for your help in troubleshooting these monitors…DELL 172FPt>white screen only

White screen is usually lcd panle fault.

/ EIZO Flexscan L355>NO POWER

You have to check the components in the primary side  and also secondary diodes too.

/ SHARP LL-T17D4-H>white screen w/ deteriorating gray-black shadow/

Also suspect lcd panel fault

MITSUBISHI RDT1710VM>powers ON then turns off after about 2secs.

Check filter cap with esr meter and make sure all the output voltages are good and if the voltages are good and still shutdown then suspect main board problem

/ HYVISION MV177AN>top 3/4size screen OK,bottom 1/4size screen pure black!

Might be LCD panel problem

Already checked and changed some of the suspected capacitors via analog multimeter but I think I still need to buy an ESR meter for me to be sure in dealing with capacitors accurately.

Yes you need one

   Can I have your opinions regarding ESR meters,I’m trying to choose between Atlas ESR60 / Capacitor Wizard / Cap Analyzer 88A / & Blue ESR meter. Would it be right for me to buy the Atlas ESR60 meter,cause this is the one available here in Japan.

I have not use atlas esr meter before but the BLUE ESR meter is real good. Again it depends on your budget.

   About DMM (Digital Multimeter) which do you prefer between SANWA 510 and FLUKE 179? As I try to venture in electronic troubleshooting.

Actually both are good meters and you can use either one and again it depends on your budget

   I would like to know also your opinions about the Leakseeker 82 from EDS, Sencore LC103, Sencore TF46 super cricket VS Atlas DCA55.

Leakseeker is good for you if you repair a board that have lots of IC’s, Sencore is good for testing caps and coils/inductors, TF46 good for checking transistors and DCA 55 i good to identify spec and type of components

   I’m planning to invest on the best accurate and reliable test equipment I could afford in the future for my plan electronic repair shop in the Philippines,thats why I’m asking your help/opinion and advice on these matter,and hopefully you could help me.

Good to hear that.




thank you so much of all efforts you have done for me so far.

the good news is i assembel the zener diod cheker and it works strongly and check all zener diods in islamic republic of iran. i want to say thank you for good digram and practical  and useful kit like this one. and please send me such as this kit if you have any more to me. i will be much thankful of you . i will send you a picture of that i just change the diods to a bridge diod as a sustitution of 4 diods 4007 and works like bullet also i change the place of panel and test wires

hope to get the esr this time i will be at your service.

best regardes




Hi Jestine

Saya ada Monitor CRT ViewSonic, masalah ialah tak boleh adjust Tilt, bila saya adjust kat OSD tiada fungsi

Terima kasih


Hi Ahmad,

Masalah tilt ini sukar nak baiki. Kamu kena cari pin kat microcontroller yg control tilt dan lepas itu trace dari sana dan harap kamu jumpa komponen yg rosak.




HI Waleed,


1-I found IC’s part number as A81DC , Q524 (IC 241) 8 legs , leg no.1(Vcc 5v ) .


This is an EEprom IC.

2-I found IC’s part number as U526, DM024, M_LEJKL7-1004, JFD38 (IC 201),42 legs, leg no. 11( Vcc 5v),


This is a Microcontroller IC


3-I found (IC 401)32 legs , leg no. 4 (Vcc 12v), but I found a heat sink on it and I did   see the part number but I see number on the a heat sink as BH63-00124A .


This could be the horizontal/vertical oscillator IC.





there is no problem in display, but sometimes it seems that the screen is going far and comes front with the intencity of the picture. all power is ok. one more thing is that I run my computer about 14hrs per day minmum. somtimes 48hrs. but at the first the CRT didn’t become so hot like now. but running time have not incresed than before. I’m afread of about the burning smell. do I fit a colling fan? is it so much necessary to use a cooling fan?



Hi Mithun,

I suggest that you open up the cover and clean up the inside (with brush and vacuum cleaner) and apply fresh solder to the joints. Normally it won’t be too hot till you have to fit a cooling fan. If you have the meter check all e-caps as a bad e-caps could make the HOT to run a bit hotter than normal.



Your Name: kraig socci
Message: hi, i have a sharp aquos and it keeps shutting off after about 10mins… i have never repaired a tv before… will your book help me do this or is for someone that kinda knows what there doing? please help…thanks kraig


Hi Kraig,

My book is for beginners and once they are  good in testing electronic components then they can venture into any electronic repair line. That means if they wants to be in the TV repair trade then they can buy a book in tv repair so that they will know which section that give problem. Once they have identified the bad section then they can use the knowledge from my book (testing electronic components ebook) to test out all components in that section and they will definitely find the culprit. Same goes if they wants to venture into LCD Monitor repair, audio repair and etc. However to some after reading my book they immediately try out the repair on their own  with the help from some of the websites below.

In your case it could be many problem from bad flyback transformer, dry joints, to bad electronic components. I suggest that you visit this link:


to isolate the problem.

If you have other question please do email me again.



Hi Boby,

I went to western union services yesterday and found that my name was not amend yet. Please let me know once my name had change-thanks.

Okay back to your question:

  • You have showed me how to measure HOT with an analog meter to the 100 ohms scale, but can you also show me how to measure with a digital meter using diode symbol. (can I also use 200 ohms scale with analog meter to measure HOT since my analog meter ranges from 200 and up)

It is not accurate to use digital meter to test out HOT as i came across digital meter test good on HOT but fail when test with analog meter.

  • To measure voltage on B+ of the fly back transformer, how will I identify that pin if there is no indication or labeled.

Trace from the output of smps. Usually it has about 45 volt then to the B+ circuit (that consist of FET) to boost the voltage up to 60 till 70 vdc. The voltage also depends on the monitor design.

And ” the power supply will increase if the B+ pin of the fly back is removed from the PCB”. What does this means? does it mean to desolder it from the PCB board? If B+ pin is desoldered/removed from the board, will I still power on the equipment and test, how will I measure or know that power supply has increase or not?

The B+ will increase a little bit because there is no load (no current draw) but again it deends on where you test the voltage. i suggest that you remove the B+ coil and test the b+ line voltage and not remove the flyback pin otherwise the B+ fet will burnt due to no load condition.



and i have one question  i am using a (DT 9205 M ) china digital multimeter and when i found reading of 100 ohm resistors select 200 ohm selector on meter there is no reading display on meter screen resistors which is less than 200 ohm this is meter fault or another


plz help me

 i will be thank full to u


shahid siddiq 


Hi Shahid,

If selecting to 200 ohm and can’t test a 100 ohm resistor, it is either the resistor or the meter have problem. Try test on other resistor value lesser than 200 ohm and still no reading suspect a bad meter.



hai sir,
i receive you guide report thanks.i have some confusion how to troubleshoot suppose television vertical line or horizontal line problem.

You should get a book on tv repair or visit this link:

and i need to know how to test the nonelectrolytic capacitor pf,ceramic capacitor,with digital multimeter or analogmeter.

All these testing method i have compiled into an ebook Testing Electronic Components

now iam working in saudi arabia may soon iback to my country i hope i want to open electronic repaire workshop.

Good to hear about your plan.

i want to buy electronic data book and what else you have i mean all type of books for repairing.

It depends on what field you are interested. If you like Tv Repair then buy TV repair book

but i do’nt know in riyadh from where can get your books and if i can get here tellme how much [saudi riyal]and from where.

My ebooks only available online and can’t get from any  bookstore.

and i have one more question television or any power supply unit suppose i inspect and found some diffective parts and replace it.but iam not sure may be still some problem how can i recover this problem without demage replaceman parts

This depends on the skill of how you test the electronic components and how well you understand about TV circuit.

.because its happened to me i tried to repaire power supply for receiver i checked and found some resistor and thyristor are shorted power supply unit.after replacemet i checked with power but again shorted resistor and thyristor so how i face this problem
without demage replacement parts.please give me some suggestion thanks.

Once you found bad components you need to check on corresponding components as well.



dear jestine i must ask you something about this problem in my brothers moniter a daewoo model since im more on tv line than moniter im askin your help have you ever came acros this problem? those mixed colours in the right side and left side only of the screen but the midille is ok as you can see in the photos i was going straight to the video amp ic on the rgb board, do you agree or could be an open resister? thanks



This suggest a bad tube and you need a tube as replacement.




Hi Bailing,

Welcome you back from the fantastic fishing trip.

Thanks and yes it was a very good trip!

I’ve read the Desposito’s Computer Monitor Troubleshooting & Repair Book, but I was not satisfied, because the monitors the book explain were too old, only two or three deflection frequency, not the modern multi frequency. Could you please introduce some modern CRT monitor books for me, I’d appreciate it.

Since after launching this book back in 1997 there seems to be no more authors for the CRT monitor repair. I suggest that you read from the Sam Goldwasser Monitor repair articles.

Today I practised my skill to open the cover of my working Samsung CRT  SyncMaster 765MB monitor. It has only two screws at the bottom, has no screws at the top. I’ve seen the service manual of similar samsung CRT monitors, they use what they call “opening Jig” to open it. But I can’t see clearly what it really is, so I use the split open tweezers ( as described in your LCD monitor repair e-book ) and blunt screwdriver to open the cover at the top, yes after spending about 2.5 hours the cover did open, but the joining part was really broken into pieces. Please see the attached photo. Do you use the same tools to open the cover of CRT & LCD monitor cover?

Yes, but in your case i will use the sharp point to poke open the cover instead of using the flat metal. Sometimes the plastic could break easily even though you are careful about it. Normally after the repair we would apply super glue.

Once I also used the split open tweezers to open my own LCD monitor but they also didn’t help me much. Could it be my split open tweezers is not good or could there be a skill that I haven’t mastered? Please also see my split tweezers photo. Could you elaborate a bit on how to use the tool?

Try sharpen the flat metal plate of the tweezers and since there are so many types of lcd monitor casing in the market, sometimes i also face difficulty in opening the cover because we do not know where the internal clip was.

The other day I repaired an AOC monitor that had a dry joint. The display will flicker when I knock the cover. This problem is simple, but the monitor has a tilted display and there are no tilt function to adjust. How do we solve this kind of problem?

Adjust the four screws that secured the picture by the side. I use to do that when repairing CRT Monitors.

Reading your repair Q/A part 32, about buying second LCD monitor; Could we see the manufacturing date of the screen without opening the cover?

No unless you can enter into the monitor service mode and open up the cover. Okay got to start my lcd monitor course now-talk to your later.



Hi Gilbert,


I just want to  correct something I wrote to you about. Pin 5, output stage of control IC is not connected to the Gate of FET. It’s actually connected to 2 resistors in series( a 10K and a 47 ohms) and on to the primary of SMPS, and yes, I do get a good reading of 297VDC . The  IC Vcc  is  at  pin  6  and it’s also ok. The gate terminal is connected to pin 8 of control IC. The Drain of the K1118 FET is connected in series with a( L501  on the PCB) and directly to Primary of  Transformer and Source connected to ground.  The Rectified power on the positive rail is taken directly to the primary of T1.

I suggest that you use the method in this link

to isolate the problem. It could be something shorted in the flyback area that had dragged down the B+ voltage. If after you have connected a light bulb according to the information from the website and it still did not light up then suspect problem in the SMPS. if it lights up then suspect the flyback area-may be a shorted primary winding or a shorted horizontal yoke coil.


Why doesn’t the stanby led light come on? 


The Stand by LED comes on when the CPU is receiving 5 volt. Have you check whether the cpu have 5 volt or not?


There are 4 voltage regulators and not one of them carry voltage more than 0.07volts.?


You the mean the 4 voltage regulators in the secondary side?



 As I explained before, the 60W light bulb does not burn brightly but does fade out after 7 seconds later.


This proof that the main components in the primary side did not have short circuit.


I really don’t know anymore. But I must say, I have done a lot of research and as a result have pick up a lot of experience.


Jestine, deep down , I don’t want to give up, I just need more experience.


Infact  every failure only made you come closer to the solution-keep up the momentum!



I do have an Oscilloscope 20 MHZ Bandwidth and I am not Sure How to connect it in circuit to take voltage measurements.?


To take voltage measurement, a digital meter will do. unless you wanted to check on the ripple of the DC output line.


Anyway, thank you for taking time to hear me out .


No problem!






Hello Jestine,

I’ve decided to keep the electronic repair guide and study from it.  Can you please help me?  I have a Maxent MX-42HPM20 Power Supply that keeps blowing the T4AH 250V P fuse on the Z-SUS board. 


The power board part number is:  3501Q00201A.  The Z-SUS board part number is:  6871QZH056B / ZSUS / KP42063K006469.


Can you please tell me how I can find the problem with the power supply board?  Or is there a common failure point with this power supply board, and a fix for it?  


Thank you for your help.  I do appreciate it.  I look forward to hearing from you soon.  I have attached pictures of these boards.   


Sincerely,  Vincent 

HI Vincent,

Normally when the fuse blow then you have to put more concentration on the semiconductor especially the power FET and power IC. Try remove the power transformer and turn it on again but this time you have to connect a 100 watt light bulb across the fuse holder (with the fuse removed) and if the light bulb still very bright and did not dim down suspect semiconductor fault (may be a shorted bridge rectifier, power fet, power ic and etc). And if it has dimmed down then suspect a shorted primary winding in the power transformer. Hope this helps!






  1. nonoy

    May 9, 2009 at 9:37 am

    Jestine Yong,


    I am fixing Philips FW17personal mini system, totally not working 2 days
    ago, i checked power supply its working, but no standby power.

    Thank you Jestine,

    Nonoy Abilar

  2. admin

    May 9, 2009 at 11:54 pm

    HI Nonoy,
    Is the CPU receiving the supply voltage?


  3. chaotic

    May 13, 2009 at 5:34 pm


    i have a crt colored television but the color of the display is red only..what is the possible troubles and repairs for i have to replace all the transistors in the crt board?

    thank you...

  4. chaotic

    May 13, 2009 at 5:39 pm


    i am repairng a sharp television but it has no power..and the plyback is producing a sound like a high voltage is present but it has no power..what is the remedy for that?

    thank you..

  5. admin

    May 14, 2009 at 10:09 pm

    HI Chaotic,

    I suggest that you isolate the problem by visiting this link:


  6. admin

    May 14, 2009 at 10:12 pm

    Hi Chaotic,

    I suggest that you check the red circuit which include the driver transistor. If possible compare the RED circuit with the Blue and Green circuit by using voltage and scope testing. From there you will have a guidance on what to check.


  7. Martin Harrold

    October 24, 2009 at 1:20 am

    I have an Acer lcd monitor model AL 1714. The power supply is correct @ 19 volts
    but I have no display. I found an open circuit 3 amp fuse on the invertor pcb. When this was replaced, the monitor indicator lamp was flashing on and off,(Orange) but still no display. Can you tell me if the capacitors that feed the individual output supplies could be at fault? and also the value of these capacitors
    Very many thanks Martin

  8. admin

    October 24, 2009 at 10:10 am

    Hi Martin,

    It can be the capacitor but the value is printed on the body and you can read it from there. It can also be some shorted semiconductors along the inverter circuit that you need to check too.



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