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Electronics Repair Questions/Answers and Testimonials- Part 44

By on April 30, 2013

I have purchased ebooks from you in the past and wonder if you could answer a question. My 51 samsung plasma went dark. I opened case and plugged in. Got 3 clicks and then went dark(never powered up). I suspected power supply but when I disconnected one of the main boards, the unit powered up properly, which leads me to believe it is that board that is bad. The caps don’t look bad, but I am going to use an esr meter on all electrolytics. Could it be that board or is the power supply not giving enough voltage. Unfortunately, I don’t have a schematic. Am I on the right track. FYI…the tv is out of warranty by 2 months. Thanks for any help you can give me.

HI Joseph,

It can be either one of the boards. Start by measuring with an analog ohm meter set to x 1 ohm on the main board connector pins. Place the red probe to cold ground and black probe to the pins and it should not give a full reading. If there is a pin that has 2 readings probably that pin (assuming you are not checking on the ground pin) along the line have shorted component.

Keep me update on this.




HI Hino,

ok you mean I can get result on capacitors site about i want & test results in PWM IC site
get result ok??? Can I do this on ic site??? will cause anything wrong happen like IC will burns or shocked if I tests dc result in this site.

You can test the power ic supply voltage regardless if the cap is using 400 or 450 volt. The 400/450 volt is the highest rating it can withstand. Just follow my ebook on how to test the power ic and you will surely can make it.


. Another one is hard to get small size capacitors on primary side location.sample 120uf 450volt if I get lower their numbers says 6.8 or 100uf but is same voltage 450volt is ok ??? Can use this???

100uf 450v is ok but not 68uf 450uf


hows about I get the same 120uf but different voltage like original is 450volt I get 400volt OR 500volt over  can use this on primary side ???

Yes you can. The reason you can use is because the voltage at the filter cap is only about 300 to 320vdc. 


HI Jackie,

I got the two books and I m currently going through them and they seem too good.

Thanks for the support!

I m inquiring whether you have no books like ” introduction to lcd tv or monitor function and repair”.

Sorry i do not have but you can get John’s ebook on LCD TV (mainly for beginners):

The other question is that I ve a 17 inches Dell monitor which had two shorted inverter transformer driver transistor. After replacing these two transistors, the power is okey and the green LED comes on but the screen is still black with a single verticle line. When you connect the signal from the computer to the monitor, the LED changes from green to orange which I think is standby. Please help what coiuld be wrong with the monitor. Regards hoping to hear from you very soon.

Try check if the MCU IC in the mainboard is getting the right supply voltage or not. If yes then I’m afraid the MCU/FLASH ROM/EEprom could have corrupted. Before that make sure the surrounding components to the transistors that you have replaced are in good condition.



Good evening

I need several opinions on this.

I have made a ground run in my workshop, brought to earth by an earthing-rod buried behind my house. I connect appliances that I work on through an isolating transformer. If I want to connect, say an lcd tv to this ground, which side should I connect, the hot ground or the cold ground?

Thanks in advance and have a good night …


HI Edward,

The cold ground is actually the earth ground. Hot ground is found in the primary power side thus It can’t be connected with the earth/cold ground. Just connect the lcd tv to earth/cold ground.



Hi Jestine,  My power supply problem solved ,after a chance meeting of a freeview installer who told me to replace the 2 electro’s  (c904 & c907 ) this I did and the unit burst into life and worked perfectly.  He said that this was the most common problem  , although they tested ok ,replacement was always necessary for some reason .    1uf 100v electro’s are not available locally ,but found 1 in a box that was at least 30 yr old but unused .  I have set the unit up on my tv and it has been going perfectly for about 2 hrs  .     Recently I have built up a LOPT/FBT/Tester and an Analog ESR Tester and both units seem to be very successful

I thank you very much for your most helpful  advice and input and I have Learnt a lot and enjoyed the challenge of this project with a successful outcome and I look forward to the next project

Thanks and Regards



quick question about voltage tolerances on a 55″ Samsung ln52a550.

I have three post on the output of the SMPS labeled 13V but I am reading only 12.38V. I have two other post labeled 13V but they read 12.91V.

Could the 12.38V be to low?

The TV turns on but I have vertical lines of all sizes and colors in the center of the screen and solid colors on the right and left sides. Nothing moves or changes. The screen does not react to the remote but I am able to turn on and off the tv with it. The start-up and shutdown music plays. That’s about it.

HI Brad,

Could you turn on the OSD menu? If the osd menu is affected then most probably the lcd panel is the problem. If not affected then it could be the t-con board, lvds cable (not seated properly or rusted) or the mainboard.



Hi Sir Jestine,

I have Just downloaded the new article Saving Repair Time. I am not done reading it but i know there is much that i could learn with that article. Thank you very much sir for letting me in this one-of-kind track of learning. How you made things as easy as it is has made all your work wonderful and worth the effort. This is what I have been searching for.

God bless you always.

Respectfully yours,




I have one unit ntc components,when I testing it uses analog millimeters set to X1 ohm.I get their result is 4ohm on both way.

may I know this results is ok for you??? Also what is their best result you accept it when you testing this component part.


Hi Hino,

This is a good component and it should have about 2 to 10 ohms.



Hi Jestine!

Will you please help me out on this LG lcd tv with display symptoms.

It can be powered on with perfect picture and sound, and display goes off after 30 – 45 minutes with it’s back light still on

Will you please help?

Your friend,


Hi Alaba,

Any OSD menu appear when you press on the menu button? If no this could mean the t-con board or the lcd panel could have problem. Make sure the lvds cable is reseated and there is good supply to the t-con board.



Hello Jestine!

This Amit here again.(India, Mumbai)

I was just reading your ebook “Trouble shooting and Repairing SMPS” & have a doubt about Hot ground & Cold ground explanation.

As mentioned in the ebook page no.112, hot ground is on the primary side & cold ground is on the secondary side. Which i understand is “earthing” on primary side & DC ground usually denoted as “GND” on the secondary side.

But then how come the picture on page 110 says that the “cold ground is the AC main supply ground” ???

Please explain & correct me if i am wrong.

Awaiting your response.



HI Amit,

Actually the house earth ground is the cold ground. Hot ground can only found in the power primary side especially the negative side of the big fat capacitor.



Dear Sir, please inform me the substitution of STV9326 as I my town there is not that particular IC. Thanks

sorry no sub for this. The best is to get the original number. You may buy from this link:



Hi what do you use for a magnifying lens to check the PCB with? And do you use a magnifier when soldering and desoldering? Thank You

Hi William,

I use normal x4, x10 and x45 magnifier glass to check on pcb components. When i do soldering I do not use magnifier glass.



HI Bhaskar,

1)One viewsonic(19”)Lcd monitor just comming the picture2sec and turnoff. u turnon buttonpress but picture is comming 2sec and turn off.In the powersuply all capacitors are changed but not recover the problem.plz give me the solution.

It may be one of the high voltage transformers or backlights is bad

2)Another viewsonic LCD(19″)Lcd Monitor the green button led flashing but the picture is not coming.plz tell me sir both lcd solutions.

If the supply to the MCU ic in the mainboard is good then the MCU ic have problem because the led signal is coming from the MCU IC.



Hi Jestine,

Jestine my interest in electronics started when i was young, i used to be found with people who knew electronics, from there i also started repairing some small equipments such as small radios, Walkman etc. My interest grow bigger and i was doing fine, i even started having customers. After some years i had my own shop. Currently i have two shops were i repair t.v’s, radio’s, monitor’s, lcd’s , cell phone’s just to mention a full. When i discovered your website i said i am now lucky because i knew with you and your help i will be able to know more. And for sure with your great articles you send to me my knowledge has realy increased and i am able to solve some problems which i was unable to solve before, i thank you Mr Jestine. My passion Justine is to fully understand electronics and become an expert in repairing all electronics equipments. I cant wait to receive more articles  and help from you sir, may God richly bless you bye.

Kevin K


Thank you for all info u provide us guys in the repair field. it helps to increase our knowledge/understanding which we overlook.

a client was gifted a cordless phone with 2-slave. it came with 3 smps adapters 120V 6.5V 500ma. could u help me in converting to 240V mains?
thanking u in anticipation
warm regards

Hi Ashley,

It is not easy to convert from 120 to 240 volt as you need to replace lots of components such as fet, big filter cap, resistors and etc. Furthermore after replacement there is no guarantee it will work. The best is to get a step up transformer.



Mr. Yong,

Thanks. I have downloaded the link. It is OK.

Please I have problem with my BUSH LCD TV 26INCHES. Whenever I switch it on, it will change channels by itself.

I gave it out for repair, it was returned the same.


Hi Samuel,

Try this link;



Jestine, The blue  ring tester, when i turn on ,two red light is blinking all the time  and if  i check  a coil or another device nothing lighting; let me know how to use it.

Thank  you


Hi Jairo,

Yes it is normal to have 2 red lights. It depends on what type of coils you want to check. This tester is for checking the smps, flyback, yoke coils and some bigger coils and not meant for small coil. The tester came with a test sample coil and you have done doing the rewind you should test it and it will show 8 LEDs. For more info you can visit the below link:



Sir jestine

The tv sharp primo model came me to with shorted HOT & a fuse open. I replace the two parts then the tv will turn on and have a raster about six seconds then after that the oscillation signal is gone but the b+ is still there. So I think the high voltage shutdown is the problem. I already replace the jungle IC, FLYBACK, eeprom ic, verticql ic, and still the problem is not solve.


Hi George,
If you have the high voltage probe then it will be good. Anyway, try check the B+ supply to make sure it is not overvoltage. Sometimes if the safety cap (usually 1600 to 2000v) open  circuit also would cause high voltage shutdown.



hi mr Jestine thank you for your kind technical information and support ,my problem is that i have a SANSUI PLASMA TV MODEL ; STY0342 and the fault is that the tv set power on and has sound but it has no image and it seems that the back light is not working .please help

Best regard


HI Vinasyen,

Plasma tv does not have backlight. In your case does the set respond to the remote control or side buttons? If the tv has sound and will respond normally then it’s likely a y-sustain or z-sustain fault.

You may need to check the fuse in the y-sustain board. Make sure you discharge the capacitor first. If the fuse blown and after replacement the fuse blow again this could mean there is some serious short circuit





You know that HP DV SERIES laptop has overheating problem .Hp a use a thermal pad but after some days it bresk.

Please sir tell me which heat compound should be used in this case.Is it arctic silver or the thermal pad….


Hi Alokesh,

Try IC Diamond and you can get it from



My good men,you are nice guy giving us all these tips…

I have bin in this for a years but every time there is something new.Thank you in advance.



hello jestine i just want to ask if it is possible to replace a 680microfarad 16v capacitor with 1000micro farad 16v because i cant find
680micofarad 16v capasitor in electronic shop

please help me!

best regards

Hi Jonathan,

Yes you can -no problem.



HI Gasant,
I have an old computer power supply which I use as an desktop power supply.

I am using output points 5v & 10v.


Am I correct to say this is an atx power supply.

No this is not an atx power supply. ATX power supply will have more output voltages and it does not have 10 volt.

I was working on a repairing an helicopter and somehow the wires touched and blew my power supply.

However here is where I need some advice.

AC power enters board but does not pass fuse. I have checked fuse with analog and digital meters. Tried the light bulb trick. Power does not go any further than the two ac points on the board.

Is this a normal behaviour of these power supplies when blown.

A normal behavior of a good power supply is that the AC supply should reach the bridge rectifier and produce the DC output. In your case, it could be component or the line circuit track that has an open circuit.



I have a problem to resolve a malfunction of a power card (EAY4050440). The TV (32LG2000)does not switch itself on – he remains in stand-by. When i heat up a little zone on the primary side with a hairdryer, the television starts up and works fine. I marked the zone in yellow. I checked up all components in this zone…unfortunately without success.

I hope you can help me for this problem.
Thanks in advance.

Hi Andy,

In this case you need to directly replace the components. Sometimes these components can breakdown when under load. You may also direct replace the optoisolator ics if it still would not work.



Hi Jairo,

HI ; Jestine a have a question. FRom the Power supply of the TV  AKAI  there are some devices  that i can not  identify  EX:   Part #   HER  303   Mouser Electronics   say  that is a rectifiers, in the board  has “D”  as diode;

This is a diode and you can use UF5404 as replacement.

another one   #  1010817    G50     Mouser say  that is    Opto-isolator  and another company say that is  opto- coupler    in the board  has P1. Also tell me how i can check.

Optoisolator and optocoupler is the same meaning.



I have a question about using the 100watt light bulb to test the 350 watt ATX power supply that had the no power issue. If there still had been a short fault present, would the bulb serve to dissipate the extra current draw thereby preventing the replaced components from being destroyed?

Hi Rick,

If there is still short circuit the 100 watt bulb will brightly light up and you know you cannot put in the fuse and turn the power supply on. You have to locate the short circuit first (mainly semiconductors) until the bulb turns dim or totally no light.



Thank you for the good work. I replaced a colour tv
motherboard. It displaid half screen leaving 3 inches vertically and
horizontally despite using all the pins provided for adjustment. Plz
use picture illustration to the solution. Thanks.

Hi David

You need to replace with the same part number of tube otherwise it will have such problem.



Hi Jestine Yong

I have a Samsung 21′ CRT Flat television.Once a morning I am watching tv but suddenly picture not comming but sound is ok.I have exparience about electronics,my question is to you what is the problem? Please give me some guideline for repair it myself.

Thanking you


Hi Zahir,

It can be any problem from no high voltage, no heater voltage, no g2 voltage or even bad picture tube. You really need to check and make sure there is high voltage from the flyback transformer. If no high voltage you need to check on B+ supply voltage.



Hi Calvince,
1.  this your latest news later on no power in hp laserjet p1006 those SMD components you were testing them with this smart twizer there are these     black ones with number like 223 , 471, 568 when testing is this the correct value that you should get on your meter reading?

Yes it should be near or exact value when testing it with my meter. If you don’t get near result you have to remove it from board and test it off board.

2.  There are some SMD component but they are grey in colour with no numbers haw will i know that they are their values and also to know either if they are burnt or they are in good condition.

They are mainly small capacitor and you can compare the value with other section of smd cap in other circuit.


Hi Mr Jestine,
First of all, I bought the receiver from my boss and recently I have been having problem with one is of channels(Surround right) output which often produce cracking sound and most of the time either very low sound or even no sound. In additional, I feel that the receiver gets very hot nowadays and what I do is put a small computer fan to draw the heat away from the top but it doesn’t solve the problem. For your info, I have tested the channel with different cables, speakers but problem still there. So I think it could be that particular channel has become faulty. Besides that I also encountered that front left and right channel on and off. I don’t expect too much of your time but i hope you can give me a wild guess because i trust your expertise in this electronics. Tonight i am going to check the basic components according to your guides, vision, hearing, smell, touch to see if I can find anything.

Thank you very much


Hi Alex,

Check the components especially the e-caps and make sure no dry joints in that channel. You can always compare the voltage/signals with the other channels.



Hello Jestine, I have a Samsung HP-R4262   plasma TV.   The on screen images  jumping  side to side, most when i  try to watch a show  or when images on screen can you please help me.


Hi Emile,

Try run the TV using aerial or Av signal to see if there is such problem not. If the problem still the same then try call out if the OSD menu is ok or not. If still the same you may need to repair/replace the CTRL board.






  1. Austin onweaba

    November 24, 2013 at 4:32 am

    helo jestine yong i am very happy as you have accepted me for you electronics repair guide thanks.

  2. Austin onweaba

    January 8, 2014 at 1:10 am

    helo jestine, i have problem with my tv set, its screen lighting white then if i press program botten it behave as if it will show AV but due to the whitness of the screen it can't show any thing in the screen, so i check and replace eeprom and jungle ic also resolder CRT board but the symptom still there so please help me.

    • Jestine Yong

      January 8, 2014 at 5:25 pm

      HI Austin,

      Sorry I have not came across such problem before. Perhaps you can lower down the screen voltage and see how it goes.


  3. Derek

    October 28, 2015 at 4:57 pm

    I am looking to get an Isolating Transformer, which was mentioned in the ebook. I would be grateful if anyone can get any recommendations.

    Another route would be to construct an Isolating Transformer, maybe with:

    Walsall Transformers 100VA Isolating Transformer, 15 V, 230 V, 400 V Primary 1 x, 230 V ac Secondary

    Product Details
    Control Panel Primary 230/400Vac with +15Vac Tap
    High quality safety and isolating transformers designed for use in control circuits and general applications
    Low loss noise laminations
    Dual standard primary winding 230 / 400Vac with +15V tap for input flexibility
    Dual secondaries are centre tapped. Earth terminal provided
    Varnish impregnated for overall protection against humidity and rusting
    Fully shrouded cage clamp terminal with voltage markings
    Detailed product specification on permanent label
    High efficiency, low regulation design

    I would appreciate any comments.

    • Jestine Yong

      October 29, 2015 at 9:49 am

      HI Derek,

      If your country is using 230 vac then you can get this unit. Before that you may need to take into consideration of the 100VA which I think is quite small. This means it can only withstand up to 100 watt max if the equipment you are repairing has a power factor of 1. If you are repairing an equipment that is rated more than 100 watt then you cannot use this transformer. In other words, the biiger the VA the better but it will cost you more.


      • Derek

        October 30, 2015 at 1:46 am

        Hi Jestine,

        Thank you for the reply and advice, I am located in the UK, the mains electric supply is 230VAC.

        So I think this transformer should do the job, though as you point out the power output is a little low.

        • Jestine Yong

          October 30, 2015 at 7:56 am

          HI Derek,
          Ok noted.


          • Ericson

            April 30, 2019 at 7:38 am

            Hi, good morning!
            How to know if the fly back transformer is bad

            • Jestine Yong

              April 30, 2019 at 1:50 pm

              Hi Ericson,

              Please visit the link below:



      • Ericson

        April 30, 2019 at 6:06 am

        I read some of the comments here in your web site and it gave me more interest. It is good enough to enhance our mind to handle electronics troubleshooting. Thank for your humble advice.


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