Don't Miss

Electronic Repair Questions/Answers and Testimonials – Part 26

By on December 28, 2008

I just want to wish you a Merry Christmas and a happy new year. I thank you for all the help you provided though out the year and May the lord bless you in a mighty way.

I have read your book so many time and every time I learn new things. I printed out all the books you sent me and I made folders out of it and add them to my library. they are wonderful and I thank you for them. I have fixes so many lcd monitors and tv’s and I am loving every minute of it. the victorious moments when that lcd monitor comes to life is beyond any description. God bless you my friend.





Hi Jestine:


How you doing i hope verything willbe ok.

‘MERRYCHRITMAS and A HAPPIEST NEWYEAR’.I wish the coming year will be a year of pease,wisdom and achivement for you.,for you are such a wonderfull kind of person.Jestine i don’t know how to thankyou and appriciate you for the aids, theaching tips and helpfull comments you are giving to all of us.As a thechician all those tips you are sending to me are very,very helpfull,and i am using them as i can THANKYOU again jestine.









HI  Jestine,   can you tell me where i can get a reasonable laser power meter to buy, also some tv/monitors schematics . Thank you. C. P


Hi C.P,
The tv schematic you can get free from and the laser power meter i guess you have to email to this website





Hi O,

Here are your questions and answers:


hi thanks for free report .please i would to you to send me report on how to use transistors in power supplies and other circuit

Sorry i do not have report on how to use transistors in power supplies and other circuit. i guess you have to refer back to those basic electronic books. Normally when a transistor bad , we just go to buy the same part number and replace it.

and also the equivalent of this horizontal transistor c3997

Try C3998.






Thanks so much for your help!  I really admire your philosophy of lending a helping hand to other aspiring repairers.


It’s too bad Malaysia is so far away – I’d love to meet you someday and thank you in person for everything you’re doing.  Please keep it up!








How are you Mr jestine young, I am very happy to meet you in internet.I am a Technician (electronic) field in sri-lanka. And I want to thanks for your electronics guides, I learn lot of things about lcd, fly back tester,esr meters,moniters circuites and so on. and i want your help forever. I talk about you with my friends,you are a great man in electronic Field Thankyou very much.





Hi Bert,

Here are your questions and answers:


Thanks for all the materials. I successfully downloaded them all.  I am just getting started with this

Thanks for the support!

, so I would like to ask you a question.   I have a 17″ Norwood Micro LCD monitor that i am fixing for my first project.  It has a flashing power LED, and the on off switch works.  When you switch it on, it makes a faint clicking sound,  and one of the CCFLs briefly flashes, in rythem with the clicking sound and flashing power LED.  I followed your test sequence:


Fuse is good, voltage in and out

filter capacitor is good.

secondary output voltage is good


Since just one of the lights flashes, and the other CCFL is also good, I’m thinking it is the inverter circuit.   I have attached a picture of the power board, and the side that doesnt work is on the left on the picture.   I think the inverter is the one marked UT35D82.    After this, I’m stuck.   Am I on the right track?

If all the output voltages are okay then suspect is the inverter circuit. First the supply voltage to the inverter ic has to be stable. next you can compare the components resistance between the top and the bottom lamp circuit. Any difference in the resistance then track from there.


Thanks for your help, I like your writing  and instruction style.

You are welcome!

If you were in Michigan, I’d come work for you for free!

Ha -ha  i got a cheap labour!


Also, could you recommend a good Oscilloscope?   I am looking at a tektronix 485 that goes to 100mhz.   Will that do?

Tektronix is a good brand and 100 mhz is good enough for electronic troubleshooting work.

Also , do you have a cheaper way to test capacitors on the board other than the Capanalyzer 88A?   It is just not in my budget right now..

What about the Blue ESR Meter at


I have a good digital MM, and I ordered an analog one.  I have also just bought a DC power supply, 0-38V 0-15A.  I am planning on getting an oscilloscope and a flyback tester as well.

If you got all the good tools and test equipment in fact you are ready to troubleshoot any kind of electronic problem. Investmentin tools and test equipment is always good for electronic repairer.


what do you recommend for soldering/desoldering?

Hakko 981 solder gun and any branded desoldering tool/pump.

What else will I need as far as tools?

Those common one like cutter, long nose plier and etc.


Thanks again,  I’m having fun!

If you have other questions please do email me again and you have fun too!


Best regards,





Hi B,

Here are your questions and answers:

Every day I surf your blog to learn something new, especially about Question and Answer. I do take note about every troubleshooting technique that you use. But because it is not my problem, I sometimes don’t get what your explanation in the answer. For example, the question goes like this:

I have a fairly new Samsung 2493HM 24in LCD that powers completely off for no reason. You can turn it right back on and it will stay on for hours again. Any idea what I should look for that would cause this?

It powers down completely just like you turned it off. No power light. You touch the power light and it fires right up to a big beautiful display and runs again for hours. I just spent 210 bucks for it and donʼt even know where to start to find this issue. I thought it powered off all the time when I bought it but every 2 to 4 hours sounds hard to diagnose.

Dry joints and sometimes it could be a bad mainboard. Bad mainboard can cause no Led OUTPUT  thus you thought it was no power. To confirm this you need to check the output voltages.




Right Jestine, the first pin of the PWM IC is connected to the primary ground. Before I didn’t do it accurately. By the way, do you know the tips to open the case of the printer or laptop power pack? It seems to be dead-sealed.


The tips is in my blog about using petrol on the edge.

My friend’s 15″ CRT monitor is not having any display when connected to computer, but the indicator lamp do turn green from amber while booting and when there is signal. The strange thing is that I could not hear the inrush current when switching it on. What could be the problem?

A missing B+ voltage to flyback transformer and missing drive signal to base of Horizontal output transistor.





hi! jestine,

how  you doin?

it’s me from israel, i’m one of yours fan.

i’m an electronic technician that i repair crt tv etc. these days there are lcd, plasma tv, i want to request to you to help me in the matter of lcd and plasma or if there is any suggestion for me.


         i’m grateful to you


             thank you!

Hi Nir,

Thanks for the emails and i guess the best for learning the lcd and plasma tv is to join my friend Mr Kent membership websites at:


Thanks and have a good day!

Best Regards,





I found a bad 2.4 M ohm resistor and naturally didn’t have a replacement. So I used 2 1M ohm and one 470k in series. Is that ok to do that in a circuit?


Hi Danny,

Yes you can but i guess a 390k is more better than 470k. Or you can get a 2 x 1.2 m resistor in series.




Just found my first shorted component using the variable DC power supply trick! J Cool!






Hi Sir,

I have a Dell 17″ Model P790 monitor. It doesn’t show display(Monogram).

Screen shows light but no display. Power OK, Horizantal voltages ok.

Please guide me, where is fault in this monitor.

Have a nice day.




Hi T.M,

Check all the RGB signal from the video pre amp ic to the RGB points of CRT board. It should show some signal with oscilloscope. Make sure the video pre amp have correct supply input.



DEAR jestine i want to test an opto-isolater as you described in your book but can i test it on board or i have to remove it thanks a lot

Hi ,

You can desolder one pin at each section (the LED or the Transistor) to test it without removing the ic. As for me i prefer to solder it out and test.





I have a question pertaining to the Blue ring tester. Can I test automotive relays or aircraft magneto coils with this tester?

Thanking you in advance,

Hi Rob,

I’m not sure about these two components. According to the spec it is designed for  B+ coil, flyback, smps and crt yoke coils. However i could also test it on the ballast/choke of the fluorescent lamp. One of my buyer told me that he could test the coil of the ignition in the car. I guess you have to get one and test it out. If you have other questions please do email me again.





dear sir,

I have a monitor i was repairing,it dont have power but i heard sound on the flyback section its like a clock ticking.can you tell me where is the problem of this one





Hi D,

It could be the Horizontal output transistor shorted or the flyback internal capacitor shorted. Sometimes it could be a shorted secondary diode too.



Dear Sir :

Have a nice day to you…….this week i have encountered a problem of a 17″ crt monitor that the menu will automatically appeared on the screen without pushing there buttons
and some icons inside the menu will be adjust sometimes decrease and sometimes increase
this type of trouble i never encountered before ever since…………

Sir maybe you have encountered this trouble already may i need your support and consideration regarding these matter………thank you very much


Hi A,
Try change all the front button and clean up the eeprom and MCU/CPU IC area. If it still the same then i guess the eeprom data had been corrupted.




            Thank you for your reply, I do not have a digital capacitance meter but I do have a Blue ESR meter. The capacitor test about 0.16 which I guess is ok for 47uf.


            I have continued to be impressed by your web site and service; therefore I intend to purchase the test electronic components E-books later tonight.


                                                Thanks again



Hi Tony,
Thanks for your support and yes the 47 uf have a good ESR ohm reading. You may visit this link to download a chart which is easier to read at:


I just received a new CCFL for a laptop and I want to know if it’s possible
to do a continuity test on it. Just to make sure it’s in good condition. I
want to execute this test because I also suspect a faulty inverter. So,
using this inverter to test my new CCFL will be of no help.

I already tried to execute a continuity on this new CCFL by setting my
multimeter on the continuity test option and applying the red probe to one
end of the CCFL and the black probe to the other end, but nothing happened.
The multimeter still displayed “1” (no beep).

If its not possible to do a continuity test on a CCFL, is there another way
to test its condition without using an inverter?

Sorry backlight (lamp) can’t be test with ohm meter. and the best is still have to test it with a working inverter.




Hi Abdul,

Here are the questions and answers:


Pls forgive me for breaking my word not to ask you more than one question at a time.

No problem

1) Are there any other PWM ICs other than UC3842 and KA3842 and what are their part Nos beacause I’ve seen in Satellite receivers & DVD players and many other p supplies an 8 pin IC in the primary side. Some have different part Nos and some have part Nos erased by the manufacturer.

There are many part number use in the smps section in many different types of electronic equipment. Some example are UC3843, UC3844, AP1200-40, SG5841, SG6841 and etc.

2) an old COMPAQ CRT monitor takes time at start up  to put picture and brightness on the screen. What could be the cause?

Weak pc tube or low heater voltage. The heater voltage should be 6.3 volt.

3) STALLION new CRT monitor has no brightness and proper colour. All the control panel adjustments are fruitless. What will be the reason??

make sure all the voltages at the crt socket are good like the R,G,B G1, G2, and heater.

4) Now I know why you stopped shipping parts. But in future if I require 2 to 5 pieces of each parts that are mostly used in (You’ll decide what parts, you know well.) HP, DELL, ACER, VIEWSONIC, SAMSUNG LCD monitors can you buy and ship them in bulk, of course with your profit.

I need to know the parts first before i can quote you. Another option is to email lavinci at to ask for the parts.


To buy Blue ESR and RING TESTER form you and save 39$ courier charges to UAE I’m still looking for some one like UAE students studying in Malaysia to buy the meters through them. If I find a proper person and send you his mailing address can you please ship the meters to that address?

Yes no problem.

Pls let me know when your book is ready for sale.


One thing I’ve to mention here is that I found many spelling and grammatical  mistakes (excuse me) in your e books and bonus reports. Well, English is not our mother tong and every human is to err.

Yes, infact English is my secondary language and my primary language here is Bahasa Malaysia. By the way my fourth book will be check by someone to eliminate spelling and grammatical error.

Sorry for the late reply as i was on Holiday.





hello sir,
i have read your article to check non polarised capacitor testing by using dick smith esr meter is it possible to check same with blue esr meter.waiting for your earliest reply.
thank you sir,

your’s student

Hi Ananda,
Yes it is the same when test with Blue ESR meter.




Hi Theo,
Thanks for the greenlight of using the testimony. Here are your questions and answers:

As you’ve always told me that I should set some goals to achieve for every year that comes by, I am set again to set my goal(s) for the year come 2009.

Yes one have to set it so that they can look forward for their achievement. Otherwise tomorrow will be another same day and same routine again. Once you have achieved your goal, the feeling will be beyond description.


I want  to integrate programming skills with electronic skills.  I am thinking to build any electronic device and programme it to serve a purpose as would be needed by anyone in this modern age of technology.  How do I go about that?


To that end I have enrolled in one IT College here in Nigeria.  They don’t teach electronics or firmware technology.  I enroll in the Java Class.  But it is all theory without practical applications  in the real life scenario.  Please Sir, do you know of any place in the internet where I would be able to take such training.  Help me find out Sir.  With your assistance I don’t think I have problems on the electronics side.  I want to learn the technology of hardwiring programs written in any Language such as Java into electronics circuits.  Am set to achieve that 2009 if possible.  Please Sir, let me know how and where I could possibly achieve that goal.

Sounds good to integrate the programming with the hardware. I once done that before during my college days and was using the c++ language to communicate with the outside world. I have forgot all the programming because my concentration was in the electronic repair. Ask from any institute that provides this type of training and i have no idea of which college is best for this from the internet. If there is a robotic course then i suggest that you go for it.

All the best!




I would like to learn about troubleshooting computer motherboard(as in check for faulty capasitors,faulty connections etc etc) and graphics card.Do you conduct such customised courses?


Hi Prakash,

Thanks for your email but sorry i do not conduct such course.




Hi Mr. Justine
How are you?
Do you know transistor J6810A?
May I get the manual, coz I can’t find it from internet.
what’s the similiar else with J6810A?
thank you for your help


Hi Andre,
I’m fine thank you. Sorry i do not have the spec of j6810 but i use c5411 as replacement. Hope this helps!






  1. LEE

    January 4, 2009 at 7:10 am

    Hi Justine
    I have found your electronic test ebook quite handy as a reference .

    Theo was asking about programming to hardware level.
    I suggest he check out
    and .
    A friend of mine use's Picaxa micros in his own circuits for industrial machines he makes.

    I also have a repair problem.
    I have an Hitachi 19 in CM715 that has started to flicker between normal
    and purple. can you point me in the right direction for diagnosis & repair.

  2. admin

    January 6, 2009 at 9:11 pm

    Hi Lee,
    Thanks for the links!In your case it could be a vga cable connection problem (loosen wires internally in the vga cable or connector) or loose connection flex cable between the mainboard and the lcd controller board.


  3. khalil

    January 10, 2009 at 11:20 am

    Hi Sir,

    I have a Dell 17″ Model P790 monitor. When i ON it, it blown it's fuse with in second.

    Please guide me, where is fault in this monitor.

    Have a nice day.

  4. admin

    January 10, 2009 at 1:33 pm

    Hi Khalil,

    Please check the bridge rectifier and if you have the time check all components in the power side. Sometimes a shorted secondary diode may also cause the power fuse to blow!


  5. irwan

    February 8, 2009 at 2:04 am

    Hi Mr Jestine. Currently i am repairing a SMPS model NFS40 for rotor monitoring system. There are not output voltage for 12v and 5v. Tried to replaced the MOSFET but still dont work. Main fuse not blown and UC3842 Vcc is available but it wont come alive. Can you give me some idea what else to check? I'm stuck in the middle. Thanks in advance!

  6. admin

    February 10, 2009 at 8:29 pm

    Hi Irwan,

    If you have check all of the components in primary side then i suggest that you check on the primary winding of smps transformer too. Sometimes a shorted components in the secondary output rail could cause no power symptom too. Hope this helps!


  7. Rudolf Seget

    February 13, 2009 at 8:23 pm

    Hello all,

    Could you please send to me a recomentation how to replace LD7575 device used in SMPS of LCD monitor. This device in no available in Czech Republic.


  8. admin

    February 13, 2009 at 11:01 pm

    Hi Rudolf,

    Try email lavinci at for the part.


  9. assad

    February 16, 2009 at 5:55 pm

    Hi! i have a problem with a computer motherboard. the capacitor on it were blown up and on top of it some brown liquid-like oozing from it. If it possible to remove and to resoldered a new one? cause the motherboard always failed when booting up the pc. thnx!

  10. admin

    February 17, 2009 at 10:07 am

    Hi Asad,

    Yes you can solder a new one but before that make sure the power supply produce output voltages within its spec if not a new cap will blow again.


  11. hans

    April 4, 2009 at 3:16 am

    Great site!
    I found (via Google, search for 2008118105925756.pdf) the part list with schematics for 19" LCD's such as Neovo F419 and some ACER models at the following URL:


  12. admin

    April 4, 2009 at 2:41 pm

    Hi Hans,

    Thanks for the link!


  13. RM

    April 20, 2010 at 1:32 am

    I have a 100 mhz oscilloscope and no experience using it. I would like to use it to test crystals on motherboards (14.318 usually). It is a phillips scope with an auto adjust feature. How could I use this scope to test a crystal? What other components might I be able to test with this scope? I have no experience with scopes at all, and most of the information I found online just confuses me more. Thanks!

  14. admin

    April 20, 2010 at 8:21 am

    HI Rm,

    I guess you may have to play around with the setting. make sure it is selected to Ac and try the time and volt per division knob till you see a sinewave.


  15. RM

    April 20, 2010 at 8:52 pm

    Thanks for the quick reply. I have observed this "sine wave" before. It was simple. I hooked both of leads of the scope to the crystal, then hit "auto adjust". Then I saw a sine wave. I didn't have to know anything else about the operation of the scope. Does simply seeing this sine wave mean that the crystal is good? Could a faulty crystal still show a sine wave? I plan to do a lot of additional reading on oscilloscopes and waveforms. I'm currently devoting most of my time to identifying and replacing bad SMD components. I ordered a new wave of meters to add to my arsenal. I just ordered the Blue ESR meter. I already have the Leakseeker 82b, but it's going to continue to collect dust until I have time to sit down and tinker with it. I also ordered a new meter - the Fluke 117. I also ordered a kill-a-watt. I'm hoping to use that to, at least grossly, observe the current draw of a circuit (I work on laptop motherboards).

  16. admin

    April 21, 2010 at 9:01 am

    HI Rm,

    If you could see the sinewave then generally the crystal and surrounding components are good. If you have the frequency meter which is much better because you can test the exact value in Megahertz. Yes, it is good to get more meters and this can cut short your troubleshooting time.

    Have a good day!


  17. Pravin Jariwala

    October 12, 2011 at 5:39 am

    Dear Sir,

    What is the solution for two transistors 2SC4834 for Sony KV S29MN1 in SMPS? Any equivalent that is available in INDIA ?

    --With Regards
    Pravin Jariwala

  18. admin

    October 12, 2011 at 6:02 am

    Hi Pravin,

    From my databook, the equivalent number for c4834 is BU306F, BUT12 AF, 2sc4130 and 2SC4161.


  19. chandrashekar

    October 24, 2011 at 8:25 am


    In sony klv 32t 400a lcd tv, 8 times Tick sound coming and Red lED lighting up but NO disply,No sound pls. help me

  20. admin

    October 24, 2011 at 12:30 pm

    HI Chandrashekar,

    Try this link to isolate the problem:

    Sony set usually use blinking LED to indicate where the problem section is. I suggest that you look for the service manual to locate the exact faulty section.


  21. jeff

    May 12, 2012 at 4:03 am

    hi jestine
    i need substitute for sg5841 any suggestion? can u email me thanx

    • Jestine Yong

      May 12, 2012 at 10:20 pm

      Hi Jeff,

      Try SG6841. The best is to use original. You can try order online at or


  22. Biswarup

    December 26, 2012 at 12:37 pm

    Hi Jestine,
    Merry Christmas to you and your family. I hope you are enjoying christmas evening.
    I have got a funny problem with a Lenovo G530 Laptop. Details are as below : 
    1. Power on from battery power only, no problems occured. 
    2. Plug in power adaptor to the laptop while laptop is on / off without any AC supply, no problems occured.
    3. If the laptop once receive the power supply through the adaptor, it shows charging, which is also quiet normal.
    4. Now, Switch off the AC line, the charging indicator on laptop, power indicator on adaptor is glowing continiously. At this time the charging indicator on the taskbar shows that the laptop is plugged in, but it is discharging.
    5. Now, I have disconnect the DC power jack from the laptop, same behaviour occurs as above (4), except  the indicator on the charger, which goes off as usual.
    At this time i have connected a multimeter to the laptop DC power jack, and receive 14.6 return voltage !!!
    After shutting down the laptop, the charging indicator lits continuously, and needs to disengage the battery to stop all abnormal activity.
    Do you have any idea about which area / component of charging section on motherboard or any other section creates this kind of funny problem.
    Waiting for your reply.
    Thanking you in advance.

    • Jestine Yong

      December 28, 2012 at 3:58 am

      Hi Biswarup,

      Have not seen such problem before. It could be the charging section or any surrounding components problem. You just need to open the Laptop and begin to check on each of the input/output pins of charger ic and see if there is any abnormal signal within this area.



Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.