Electronic Repair Questions/Answeres and Testimonials- Part 45
This December 2009 article is really helpful.
I particularly liked the section on “Where to get ideas to create the
Thanks for your suggestion on how to make my goal a little more attainable.
I read your book and it was one of the intresting books i’ve ever read thank you but most af all i thank God for giving you such wisdom and guidance, i know i’ll become a proffessional electrician through your assistance. thank you and may you have a wonderful and blessed new year.
Sir good pm!!
Sir can you give me the links about the video on “how to crack bios password”?.i have seen it in your website few weeks ago but its all gone now!
Try this link:
Sir i am planning to build a LOPT/FTB tester but i have some few problems for now,can i use ceramic or mylar or just any non polarize capacitors in the same value of 0.047 and 0.01uF instead of .047uF MKT & .01uF MKT..Coz there is no stock of that type of capacitors in our local store here..and i am not also familiar on that caps too..thanks sir
Yes you can try that.
Bingo you are absolutely correct the Toshiba Boombeat 29″ TV that I send for repair came back to me and the fault is dry joint wow Jestine Thx for your consultation. So now I would like to share with you about amplifier systems. I have a set the right speaker with sound but the left speaker without sound, and also my PC system amplifier right with sound left no sound can I ask for knowledge what’s the problem??
Thanks for valuable knowledge.
The easiest way to repair the speaker that one side have no sound is to do comparison between the circuit especially checking the circuit with scope ans voltage testing.
I like to ask about how to use a rework station with good?
I mean about the speed of the fan, the temperature, how long to blow the component, and what should we give to the component so we can take the component fast without burning on it.
This you have to test it on your own by using different junk board. As for my setting to remove a spider chip, i would usually set to 450 Degree celcius and the wind speed to 6 or 7.
When i first repair my monitor BENQ T705 it has no power problem. When i heck it, i found 3 components that are shorted. Two transistor C5707 and one P-Channel fet. I replace the 2 transistor with the same part number but the fet i replace it with FU9024N coz i can’t find the FQU11P06. I also found one pico fuse open. I also resolder the inverter transformer just to make sure that no dry joints on this pin of the transformer. After replacing all the faulty components, i test and switch on the monitor. And now the power is on, the LED power indicator turns into green ligth, the BenQ Logo start Display appeared also and follows the no signal detected because no computer connected to the monitor. After this condition the LED indicator became orange. So i pressume it was normal. When i connect to my PC, and turn on the power it start to boot and i can see the display on the screen then after a while it goes black. I think my monitor now have a Shutdown problem. Can you please give an idea what causes this trouble?
Have you check the tuning cap around the high voltage transformer. If i’m not mistaken the FU9024N cannot be use to substitute for FQU11P06. YOU need the original part number.
How are you, Ihope you are well, I need to ask how I can test PF Capacitors in DMM.
You need a digital capacitance meter.
Thanks for the knowledge for the amplifier sound problem, but as I know my friend technician doesn’t have a scope, so how he repair I know not.
If he does not have a scope then i guess he may need to do voltage testing or just test out all components in the faulty section.
Another fault I like to share is the Toshiba Boombeat that was repaired OKay , but now after a few days the problem is the vertical problem. When I switch on the vertical line fills 1/3 screen but when after about 5 to 10 minutes it fills the whole screen and it’s normal again, I mean it’s okay when it’s hot I mean warm up. So may I ask Jestine Sir what’s the fault before I send it back for repair. Thanks Jestine for all the trouble that I gave you, you are really patience with all that I ask for.
The problem could be a dry joints in the horizontal side area especially the flyback and the horizontal yoke area. Guess you may need to open it up and check for the dry joints.
I test the secondary winding of the chopper transformer which I think its OPEN with the use of flyback tester but only the first light is ON. but when I check with analog tester set to x10k still no reading. I forgot to tell that I remove the chopper from the circuit.
Flyback tester can’t be used to check on secondary winding because it has less turns. How to you know which secondary windings to which-do you have the transformer diagram? If you have then Yes it has an open circuit if no response from your analog meter.
i want to ask you question about logic probe
you said that the truth table is important to use logic probe
i cannot find the relation both of them i read in many forums that when green led light up that mean low voltage
red led means hi voltage and i didnot use logic probe ……………………..and i donnot know how the truth table is important to do this job
You need to get a logic probe to test on board that have the TTL ICs.Find the IC part number and then to see which type the IC belong to whether is OR GATE, NAND GATE and etc. From there, refer to the OR GATE, NAND GATE truth table and test it with your probe with power On to the board you are testing.
Thanks for the info.
Actaully yesterday i already test the tuninng capacitor and my capacitance meter reads around 224. The actual value of the capacitor is .22 160. What kind of capacitor is this? A rectangular in shape and color gray. Is it .22microfarad 160V?
Yes, that’s right. It is a metallized polyester film capacitor:
Today i check it again and found out Leaky and i see a bulge beside the cap. I take out to the circuit and check it with the capacitance meter it’s now no reading. I also check it with my analog tester and set it to X10K the meter move a little i think it’s leaky, compared to the good one the meter does no move at all . Since i have the same BenQ monitor with the same model, i take out the known good capcitor and replace the faulty one. Again i test the monitor but still it shutdown.
Sometimes it could fail when test with Blue ESR meter.
Now my only supect is the inverter IC and the inverter transformer. Since it’s not easy to remove the IC because i don’t have the SMD rework station. First i check the inverter transformer. Unpluging the monitor and touching the inverter transformer one by one, i found one transformer have a little hot compared to the 3 transformer. Now i already have the clue. This transformer is the area where the faulty transistor and fet components are connected. It also control the top backlight. I removed it from the board and check it with my analog tester but i think it’s good. I check first the secondary winding setting my analog tester to x10 and i got 60 ohm. testing the primary winding, I set my tester to X1 ohm range and the meter reads to almost zero. I also test the primary and secondary winding for short, fortunately there is no short circuit on the winding. Since i don’t have a blue ring tester, the only solution is to take out the inverter transformer from the good inverter board and replace it to the board that has trouble. After replacement of inverter transformer, i test it on. Switching the button the BenQ logo appers followed by the no signal connected and observe the display if it ‘s quickly disapper. From my observation the the No Signal Connected displays a little bit longer for 20seconds compared to last time in which the display comes out then quickly shutdown. Now i connect it to my PC and test it on. Presto!
Now the monitor don’t shutdown anymore and the display was so clear. By the way, why the primary winding has 6 pins?
What are the pins that are connected to each other?
This is the way it suppose to be connected by the design engineers so that it can drive the push pull transistors.
The transformer number is 19.26048.001 under this number is T0115A5100541. What is the right part number on this transformer?
So, the culprit is the inverter transformer, thus causing the monitor to shutdown.
Again i would like to thank you for your guidance and the full support for us. Long Live and God Bless!!!
Most Tvs i handle do not use an IC in the primary but rather have two transisors or one and a FET.For example a tv may have BU809 and C3870.Have you ever come a cross such like?Kindly help on how the switching starts.
Yes i had but those were very old models. The switching start from the components that forms the oscillator circuit.
Thanks for your fast reply!. can I please ask you another question, I have this monitor (CRT) the problem is
when switch on the green led blinks on and off and you can hear a flickering sound. when opened and checked the components I found the HOT shorted so I replaced it with an exact new Hot, when switch on again it only worked for 3 seconds and shorted again, I am suspecting a bad Fly back transformer I guess that the flickering sound is coming from it. Thanks in advance for you Help
Please refer to this link:
Hope you are doing great!!
Yes, I’m doing great-thanks!
I’m using a Philips 104E 14” monitor. When I use it, it goes off suddenly (no even standby LED) and then it couldn’t be turn on. When it’s working I can’t control the horizontal width even with the control battens. I did following troubleshooting steps :
1. All dry-joints were soldered.
2.horizontal transistor TIP122 and H-Out transistor were replaced with new ones but problem still remain same.
3 .then in order to check the voltage at H-out transistor, 230V bulb was connected to the points where E and C of the H-out transistor were connected. (and H-out was removed from the board )When I turn on the monitor I found the bulb is blinking (this is abnormal and fixed voltage should come to the h-out Tr, I think.)
******After removing the H-out transistor amber color LED came up.
Can this be a Fly-back issue? Please guide how to troubleshoot this
I suggest that you visit this link to isolate the problem first.
It may be flyback or power supply problem.
Check this link also:
I came across the width problem was caused by bad modulation diode, bad flyback or even corrupted eerprom data.
I’m confused with my monitor repair.In your previous email, you told me to remove the IC and check the voltage,if not then replace the IC.
Yes, check the dc voltage to see if it still fluctuating or not.
Today I try to buy the IC,but my fiend said that this KA3842B IC if it is deffective the monitor would completely dead,
No not necessary as some bad ic could cause display to have problem, power blink, and fluctuating in the supply voltage to the power IC.
If there is still a voltage than the IC is okay,but the surrounding component is the problem.
Made sure the supply voltage is stable.
It’s very hard to find that IC in my city.I direct replace the ceramic capacitor at surrounding,but the result is still the same.
Try use UC3842.
I’m sorry Mr.Jestine,it’s not that I doubt you, but can you give me an explanation why this IC can make the voltage fluctuating?
Any shorted or leaked semiconductor could cause the line to fluctuate. Let’s take a shorted HOT for example, it can cause the B+ line to fluctuate or no voltage at all.
Don’t you think it’s not because of shorted secondary area?
It is good to check the secondary side as a shorted component in secondary side can also cause the primary side voltage to fluctuate.
Cause the secondary area is 0 voltage.
The fluctuating is fast at first, and then get slower and the power led is on and off also.
If the power LED is on and off that’s mean the secondary side have output (not zero volt). Have you isolate the power supply by using the light bulb?
Dear Mr Jestine,
I have already download your free report. Nowdays almost every television manufacturer using chips components in their circuit, It’s quite difficult to repair it. Do you have some suggestion to solve this problem?
I am from
If it is the chip problem than yes it will be difficult to buy parts. The actual fact is that not every time the problem must be the chip. It could be dry joints, bad caps, open resistor and etc.
If you need to start your business, i suggest that you secure your customer base first before coming out. Once you already built up the base, it would be easier for you as you don’t need to worry about where to get customer because now your overhead will be high. Hope this helps!
Thanks a lot for your e -mail.I have always envisioned myself in a good workshop and getting equipments for repair because of what i am able to do.I always have a dream that one day i will be in a position to be a qualified technician.The challenge though here is the cost of a tool kit and books.They a very expensive.An oscilloscope for example is an affordable for a common technician and i have never come-by any in other workshops.I do not know whether it is still possible for one to do well in repairs with only a digital and analog meter.
Thanks for your email. Meters is just like our helpers and without them it will take a longer time to find out the fault. In this repair field, time is money and the faster we solve a problem the more time we will have for another repair. Save your money first as a succesful repair tech can’t afford to have no good meters on their repair bench.
i really thank you
and i say some notice in order to comment about it
-lets say that pin which i test is AND gate thus my truth table is this
in out put i have three 0=L=GREEN LED
and one 1=h=red led
then i should see the green led light three times and redled light once …
ok or i am wrong
****i put the ground wire on known ground
positive wire on voltage line 5-15volt
Okay don’t be confuse. Let’s take the AND GATE for example. If the input a and input b reading are high (1) then expect the output to have high (1). In the next case where there was an inverter at the output thus if your input A and input B are high (1) then the output is High but because it go through the inverter, so your output will become low (0).
hi sir Jestine can i ask? what kind of part is J598 (Q751 and Q743) thats all thank you very mush…
J means 2SJ which is a p-channel FET.
Selamat pagi En. Jestine,
Merujuk kepada buku En. Jestine bilangan muka
Nilai 195? tiada, yang ada hanya 180? dan 220? nilai yang terhampir, adakah yang lebih besar nilainya
Lebih baik daripada yang kecil itu. Terima kasih banyak.
Anda boleh menggunakan 2 perintang dalam siri untuk mencapai nilai 195ohm. Guna 180ohm siri dgn 15ohm dan anda akan dapat 195 ohm.
Two days ago a customer sent me a super big CRT monitor that I have ever seen for repair, this is a professional monitor and has RGB input.
Every time I check a big professional monitor problem, I find that their circuit ( especially HOT section ) is a rather different from usual small monitor. Like this one is using C5584 as a HOT, but its collector doesn’t connect to any pin of the primary winding of the FBT. Do you think this transistor is really a HOT, or maybe another transistor which I haven’t found on the board?
This type of design is different than the common Monitor. One HOT to drive flyback and the other HOT is for horizontal yoke coil. Try read joe desposito monitor repair book at page 111 starting from the first paragraph.
The mainboard circuit is really full packed with components, and I found a small board stacked on the mainboard in its power section. Analyzing this kind of circuit is really time consuming since I haven’t got the schematic. See the photos.
Yes, it will consume lots of time to repair such Monitor.
The problem of this monitor is arcing heard when turned on, and I found the internal capacitor value is only 0.9 nF. What is the normal internal capacitor value for this big monitor?
I think is about from 3 to 4.5nf.
Is it possible that the FBT is driven a MOSFET instead of a bipolar transistor? Have you ever found this kind of circuit?
Please refer to the first answer. Sometimes the P-channel B+ fet shorted could cause a higher than normal voltage to the flyback thus causing the flyback to arc.
I got difficulty in analyzing this monitor circuit. Do you know where are those two primary pins connected?
Once you know how this circuit work (base on joe desposito book) you will be able to trace the primary pins.
Your Name: Agung K.W
Message: Jestine, thank you for all tips you’ve sent to me. Those tips trully incredible. I can practice my ability in managing all the repair works, inspired by all of your tips and trully they give positive inducement especially for young beginner. Thank you Jestine, for your good advice all my friends know spend more of their time to learn electronic and how they can make use of it as their primary source of living. GBU
In some monitor that I repaired, I only see the Posistor but there is no relay in its vicinity, only relay marking on the board but no relay component installed. Do you think the degaussing coil circuit would work without this relay?
This circuit do not have the push button degauss and it will degauss automatically the moment you turn on the power. I believe this is an old Monitor.
Also I see in some older monitor, the posistor has 3 pins; but in the newer monitor the posistor only has 2 pins. What are the difference?
Good question. I actually did not break these posistors and see the difference thus i could not answer you this.
Could I use the 2 pin posistor in a 3 pin’s posistor circuit or vice versa?
I have not try that since i could easily get the 2 and the 3 pins posistor. However, i believe it is not the same because the 2 and the 3 pins posistor have their legs connected to circuit.
Could we check this posistor using analog meter?
No you can’t as i came across posistor that blow the fuse have a good reading when compare with another good posistor. If you suspect the posistor have problem you have to directly replace it.
Today when I repair LG 15″ Studioworks 505G monitor, I didn’t work with 1024×768 resolution with 70Hz refresh rate, the display says “out of frequency”. Do you think this is normal or a repair fellow had made it so? It’s rather strange to me because I often repair this model of monitor, only this one got the error message. See the photo.
Sometimes a same monitor have different version. It may be the problem of bad eeprom and cpu.
The other day when I had worked on LG 452V monitor, and checked it with RGB purity, the display always brighter on the right edge. What could be the problem? It’s a pitty that I had not taken the photo of it.
If you can’t remove the purity problem with a demagnetizer then suspect a bad TUBE.
Your Name: Hassan Farouk
Message: Greet for all
i HAVE MONITOR LG 710 E I WANT CHANG SOCKET THE CABLE I WANT KNOW HOW STEPS TO END THIS WORK AND I WANT KNOW WHAT THE COLOR FIRST AND LAST
Try visit this link:
The color of the signal cable is not standard thus you need to find it out from the VGA head.
Can i change Bu1508dx with Bu1508ax.?
Some monitor can support and some don’t as i came across some monitor can only run good using the original part number.
Can i directly change if a
If it arc out then you have to replace the
How to find out the value of a colour coded non polarity
capacitors(found in an old philips tv).?
What are all the Common faults in a remote.?
Dry joints and cracked circuit lines
Same to you and family Merry Christmas.
Thanks, only the problem is how to get the parts,that is a bigger problem,when you want 1 or 2 parts ,the most companys will only delever when you thake for more than 50$.so you have a lot of parts what you mayby never will needed any more,while te parts are differend evry time there is a new type monitor on the market.So i need a IC for a samsung monitor,no wan wont deliver the part.its a backlicht inferter ic FAN 7314m. i’m living in the
Have you try here:
1. At a glance, how to recognise a eletrolytic condeneser filter capacitor?Its functions are to store and filter any irritance or excess voltage?
The link below is electrolytic capacitor
Function is to store current and remove ripple.
2. I noticed there are white powder paste between certain transistor and the heatsink.
What is this white powder paste? What is it for? How many type of such white powder paste are there which are used in electronic components?
Those are heat compound and is use to transfer heat so that the transistor or semiconductor would not get hot easily. Usually there is only one type but with many different brand. Just ask for heat compound and the seller would understand.
3. I hav a rechargeable battery which I use for my air pump fish acquarium. Its type “regulated of sealed lead acid”-NP.1.2-12 & 12C 1.2Ah. It is 100% memory free.Can I use a car 12V DC charger to charge this battery?
I suggest that you don’t charge it as the car battery charger is meant for only car batteries.
I dare not do anything now as afraid it might explode. If cannot, can you guide me to what type of charger to use to charge it or guide me to a circuit diagram so that I can built one to charge this battery.
May i know what’s wrong with the seal lead acid battery? Do you mean that the original seal lead acid battery charger have problem? I could not find the seal lead acid battery charger circuit but i found a simple car battery charger circuit at:
4. I noticed shape/physical features of transistors are different. Eg. the HOT-C5148 is different in shape/size and features from small ordinary tranisistor like C516. How to recognise each components as transistors and I presume they perform same function, but for a different reasons?
You have to get the datasheet from the internet and see the spec of those transistors. Yes you are right, they have the same function which is to switch but meant for different reasons. It depends on circuit design.
5. I also noitced in your “how to repair writeup” each month, you have not touch on popular electronic products in Malaysia like Panasonic,Toshiba,Phillips, Sharp, Hitachi, Samsung etc(for LCD TV, LCD Monitor etc..). May I suggestt you take a peek at some of them for a change?
Usually my repair article is about understanding the principle of electronic repair. That means once you understand the principle you can repair any type of electronic equipment.
6. How to recognise or differenciate the various section of PCB like…power supply area, audio section, video section..etc…? Your tips most welcome.
You have to get a board and study it. The Ac voltage input to that section is the power supply area. For audio, trace from the speakers and see where the line is coming from-that section is the audio section. Video is usually at the CRT board.
Hi Jestine, I was reviewing all the information of your curse, but I have a few questions: for example I have a Gateway FPD1830 LCD monitor that gives images just for a few seconds then the screen gests black the power led is on, according with a troubleshooting from MoniServ web site the problem is the inverter so they have inverters in stock for that monitor for $89 Dolls. Ok my question is your curse is going to guide me to diagnose the problem, then let me know that I have to buy the whole inverter or it is going to guide me to troubleshoot which part is the one that is not working like a resistor, or capacitor, or transistor, etc, to replace one of them? Other question here is for example for the inverter for the Gateway LCD monitor every component or the inverter board can be troubleshoot and replace or there are some of them that can not be replaced? That way the cost of the reparation will be less expensive.
Other question is do I have to buy expensive tools like the oscilloscpope to repair lcd monitors?
The last question is: long time ago I studied basic electronic so I have some knowledge on electronic how much knowledge do I have to have to start repairing lcd monitors and other electronic devices?
Thanks for your interest in my ebook. Getting started on the lcd monitor repair must have so me knowledge in testing electronic components. If your intention is just to repair that Monitor then it is not advisable for you to buy it. However, if you have a lomg term plan of repairing more electronic equipment then i guess you may need this lcd monitor repair ebook plus the Testing Electronic Components ebook. In your case the problem can be bad backlight, bad filter cap, dry joints and etc. My ebook does cover this type of problem but not specific to Gateway Monitor. I’m teaching principle of electronic repair. That means once you know the principle you will know the rest.
Besides, i do provide support to my buyers and this is a great way of making you to become good in electronic repair. If you have other question please do email me again.
Dear Mr Jestine,
I got this LG 15″ CRT that very brigth,even the brightness setting is at 0.Can you help me to restore it,cause the screen setting at the flyback is glued,so I cannot adjust it,may be is there another way beside adjusting at the flyback?
Make sure the G1 voltge is not zero volt otherwise it will become very bright. Try put in some thinner to remove the glue.
Since we know that there are two kinds of transistor i.e: silicon and germanium, do you also find the Ge transistor is used in monitor circuit?
No, i have not seen any of this transistor even back in the early 90’s
The flyback pins are important info for us as a repairman, but none of the books in my bookshelf explain it, even the Desposito’s book. Could you suggest some books or website which explain in detail about the flyback pin configuration?
There are no books in the market that explain about the flyback pin. I spent lots of time to analyze it.
One of your article about finding the ABL pin, mention that one of the flyback pin is something to do with VCC. Could you please elaborate more on this pin: where is it connected to, how high is the VCC voltage etc.
VCC pin rarely found in Monitor flyback but for TV flyback yes. The flyback produce the Vac and converted to VDC by diode to supply to vertical IC and other circuits.
How would you define your 3 months repair warranty period? I mean suppose trouble comes again within the three months warranty period and the monitor is sent to you again; then the time which is used to repair the monitor again is counted in or out the warranty period? After the set is sent back to customer for the second time, how would you define the left over warranty time?
Because of competition is so great, we have to cover warranty even though it is not the original problem. That means, if the actual fault is No power and second time came in with no display symptom, we still give warranty to the customer. No matter what problem it is we will cover it till 3 months. Because of this we have to make sure we do our part as good as possible. After any repair, we would knock on the monitor to make sure there is no dry joints. We would also do a proper burn in test. Out of 40 to 50 repair, there will be a case or two with warranty problem but this problem is still acceptable.
When repairing LCD monitor are we allowed to use the part which has different package type as long as the main type number and total pins are the same?
Generally, as long as the part number is the same then you can use it. However i came across C5707 transistors that have shorter legs caused problem. I suggest that you retest to see how is the behavior of the LCD Monitor after replacement with different type of package.
but it’s writen on the main cap that it provides 450 VDC , switch mode i dont know how to check the output voltage for it.
450VDC means the cap could withstand until 450vdc. That means the voltage that passes thru the cap should be less than 450Vdc. In your case it should be around 300 to 330 vdc. As how to check the voltage in smps i suggest that you get my ebook LCD Monitor repair as it has photos to show you how to perform the right voltage check.
Your Name: Sanjay
Message: Pls,can you help for How to check RFI suppression capacitor.
Just use a digital capacitance meter will do.
Hi Jestine yong,
Ya I received your report on SMPS.Thank you
I am a software engineer in
I have made a small book let about “how to maintain TV” for general use…have distributed 5000 copies in surrounding area. I request other people to try the same thing in which they can put their advertise also.
My one more question is “is LCD tv is repairable by any person who knows basic electronics” or “any special skill and software knowledge is required?”.
If any starter can repair means there is no much scope for that I think.
Please suggest regarding this.
-thanks and regards
If the guy that have basic electronic repair experience and willing to invest on LCD TV repair information and diligently visit LCD TV repair forum, i don’t see why he could not repair the TV. The fact is many of those who have some basic electronic repair do not really go further than that to acquire more repair skill. Nice to know you too!