Don't Miss

Electronic Repair Questions/Answers and Testimonials- Part 57

By on June 23, 2010

Respected sir,
i have got a lot of technical knowledge from you .
thanks for your worm regard .god bless you .







I noticed that one of my monitors which is dell 172fpb LCD shows a padlock icon which sometimes goes lock and unlocked. it appears even while i’m typing or in an idle.


Hope to hear you soon.


Engr. Rogelio G. Tiglao


HI Rogelio,

I came across this problem in Philip Monitor but not in Dell. The cause of the problem was in the MCU.





HI Felix,

How are you doing?

I’m fine thank you.

i want to say that i really appreciate the newsletter you have been sending to me.

You are welcome!

it fun having you by my side atleast i can boast of becoming an electronic engr.

but i’m have a problem with my computer mother board. there is light on the motherboard but the computer can’t boot so i feel there is a resistor resisting the flow of current from circulating the board.

You may need to check the supply voltage. A motherboard won’t boot could be the problem of power supply too and not necessary have to be in motherboard.

Have a good day!





HI Narendra,

thank u sir a great post frm ur part…

You are welcome!


1que. in my mind….was tht i hav a Philips 21” inch t.v

in Powervision series…fornt panel’s power led red light

blinking continuously…when turn on t.v….when i call an expert …he told that its Main Function IC 8361 is in prblm…bt sir if t.v. on  it works fine for whole day…nxt day same problem…can u suggest the acual reason…

It could be intermittent problem and you need to find dry joints. Sometimes a bad -cap in power or secondary side may cause this problem too.





I just wanted you to know that the notes and guidlines thatyou sent across to me have helped mw a lot. Im now a popular electronics repair in my area. Keep on sending more.


Thank you


Best regards.
Brisco L Tadubana



DEAR JESTINE Thanks you very much for this version which is for me more pratical . you always know what we need . Its is a wonderful and very useful, full of  know how once more my gratitude. God bless you James K HongKong




hi Mr.Yong im from philippines..please Help me to fix my NEC Multisync 1740CX LCD monitor That Problem is when turn I ON my LCD  Monitor after 3 seconds is shutdown the light of a monitor..

Thank you very much and God Bless you.



HI Jeson,

Check for dry joints, bad e-caps and bad backlight.




hi jestine,


im repairing computer mainboard, with the restart symptoms


and i found out few leaky solid state capacitor.


my problem is identifying the value, coz it do not contain the usual markings.


i attached the picture of the capacitor, so that you can see the markings.


pls help me find the value.


thank you!


Hi Charles,

All these smd caps have their own coding from manufacturers and usually they rarely reveal it out. From the photo it seems that it is a 560uf cap and as for the voltage just use a 25 volt cap.





Hi Jestine,

I would like to say thank you for the information, as i have repaired my first Monitor ( LG power supply problem with 2 blown capacitors ), thank you so much.

Sid Khan




HI Waleed,

I hope you had a wonderful time on your vacation.

Yes my family and i enjoyed it very much.

I have a question for you. I have this lcd hd computer screen that smoked when I turned it on..when I checked it out..found that one of ballast capacitor J18 3KV that has a burn in the center of it. there are three ballast capacitors on that back light..I think the middle one is Protection? please correct me if I am wrong..

You mean which cap is to the feedback circuit?

the question is what causes the capacitors to burn like this..and what is the power rate that I can go down too..

There are many factors like quality, the environment (usually very hot inside the lcd monitor), bad corresponding components and etc.

I found capacitors are are only it safe to replace it with a lower volatage ratings and what J18 stands for? thanks

18 means 18 picofard and j is 5% if according to the standard code. Sometimes different manufacturers may have label it differently. 3 kv is safer but you can try on 2 kv, Try on/off for many times to see if the cap can withstand the peak start up voltage or not.





hie jestine i would like to thank you for all the help you give me on
repairing my stuff. i am not much of an electronics guy but i now feel
that i am capable of handling a lot of faults through your help. you
have upgraded my mind and i say thanks again .






Hola, Jestine mi pregunta es la siguiente tengo un LCD samsung modelo LN-S4095DX el cual el video esta bien pero no tiene audio, ya revise los parlantes,tampoco sale audio por los auriculares.,cual podria ser el defecto. Atentamente. ossian



Hola Ossian,

Es posible que deba revisar la sección de amplificador en el monitor. Asegúrese de que hay tensión de alimentación del ic amplificador.





Thank you for the responsed, I am very appreciated of what you doing for me. The voltage that I am trying to stablize is around 184- max 195vdc as per. manufacturer. But I can’t seem to do that it would start up when power up at 166vdc then within every second it would rise 1vdc until it reach the overloading safety margin then shut down. I believed for the overload to shut down on this SMPS as I measure is around 210vdc. Hope you can help out and I am very greatful to have someone like you to help out. If I want to attend your classes in electronics how do I go about register? I would love to learn more about electronics.



Phil Vu


HI Phil,

May be you can try to connect a 100 watt light bulb as a load so that the smps would not shutdown. At current moment we no longer taking in international applicants-sorry about this.






HI Abdul,


First of all “BIG THANKS” for your monthly news letters.  Quite frankly they are well informative and deals in latest practical problems. I strongly recommend all the technicians around the globe to follow WITHOUT FAIL your NEWS LETTERS and the books that you have published. Also from the bottom of my heart I can say that you are a constant source of “PRACTICAL GUIDE & KNOWLEDGE” to all the E.technicians around the globe.



   Mr J Yong, I have a problem, My MOM’S SONY Tv Model no. KV-XF-29M65, Memory IC No. 24C08A got defective and is not available in the Sony service centre  & local market. Is it possible  that we can bye a not programed IC and write data on it ? If not then in your view  what is the best solution ?

If we can program the memory IC ourselves, Then can you pl guide me HOW TO DO IT ?.  IC no. 24C08A not programmed is available in the market

The data can’t be programmed into a blank ic. The reason for it is because the eeprom ic have lots of hex file and it can only be done by the programmer who wrote the program. You need to have the same ic in order to program on another ic using a programmer.
The best solution is you may need to search for the right forum to ask for the information.





Message: hi, great site but skiming tro your poer supply section i could not find a suloution to my problem, I’m a tattooist and have a dual power supply DT-P025. the problem is the display ( it showes volts, duty cycle, Hz and cps ) seems to be eratic and wont show a stedy reading, its not my tattoo machines that cause it or any of my equment. Im normaly great at trouble shooting but this has me stumped, any help would be greatly apreciated…………..thanks for your time and help



HI Kyle,

Erratic problem could be due to dry joints or even bad filter capacitors that you need to check it out.




HI Humberto,

I have a question about the future of electronic repair. Since electronic components keep getting smaller and more condensed soon the only thing available for repair will be replacement of board like a computer motherboard. If this becomes a trend then what will this business model look like. I love electronic repair but computer/network support seems to be the only logical next step for an electronic technician. What are you thoughts on this? There are very few electronic repair courses in my town. My friend tells me that electronic repair to component level will be history within the next 20 years. Everything will be surface mount.

Do not worry about this trend as i believe somehow there will be solution for this. Look at the motherboard of laptop (all smd components), lots of people say it can’t be repaired but how come those repair tech from China managed to repair them? This is because they could get the parts and their country have the resources for it. If one would go to China to source those components i believe they will find it. The switch mode power supply will still use bigger components. Look at the LCD TV, the panel is thin but the power supply is still using bigger components. Don’t stop and keep on learning and visiting forum to get the latest tips on board repair.

Have a good day!





Good day sir,


Have here an LG 19″ LCD monitor, and with no power. Suspected part failure is its PWM 8-pin IC, with a value of LAF0001. However, said ic is difiicult to find. Can you help me in finding an equivalent part substitue for said IC.


Your reply on this matter is very much appreciated. Thanks in advance.


Respectfully yours,




HI John,

Try this link:

I have good comment about his website but if you order less the shipping fees would be slightly expensive.





Hi jestine, can you please help me with my tv that has a rolling picture from bottom to top and the one that is showing a key, thanks.


HI Nozick,

Rolling to top could be missing vertical signal and you need to trace it in the vertical oscillator side. You may need to replace the vertical oscillator and retest. About showing a key, i guess the eeprom IC may have locked and you need to check with the distributor on how to unlock it with the remote control. Make sure also the supply voltage to the eeprom ic is good.





Hello Justine..saya sedang membaiki LCD komputer brand Acer.Masalahnya bila on selama 20 Minit Display dia hilang dan bila saya switch off dan on semula display dia ada tapi padam semula setelah beberapa saat.Saya dah check semua e-cap dalam keadaan baik dan tiada dry joint dan saya resolder balik pada kaki2 komponen yang kekurangan solder tapi masih juga problem.Pada fikiran you apa yang menyebabkan LCD  jadi begini?Saya berharap sangat saudara Justine dapat membantu saya.

Sekian,terima kasih.

Yang benar,


Hi Noorishkandar,

Cuba check backlight kerana salah satu backlight rosak boleh menyebabkan ia shutdown.






Hi Jestine,


Need your expert advice.


This 15″ CRT monitor came in with NO Display but have power. Upon checking, there’s raster as well. When I increase the screen knot on the flyback, I can see the white screen but No character/graphic. What’s the appropriate/effective method to troubleshoot this problem.


Thank you in advance for your time & effort.


Best Regards,

Chii Tieng.


HI Tang,

That’s mean contrast or ABL line have problem. Replace the video pre-amp ic or trace from the contrast pin in the video pre-amp to the flyback abl pin. An open resistor or shorted cap ca cause this kind of problem. I came across also an ACER 15″ Monitor with the same symptom and the problem was the eeprom data. Reprogrammed the eeprom ic solved the problem.






I have an lcd screen..that is making tikking noise and there is no relay in there. there is some capacitors that are gone bad..but that is not the problem..the problem is there is an smd diode that is burnt in there that goes under the bad capacitors but from the other side of the PC. it is burnt but on the says ZD9v. on the diode itself says..7.5 and under it 9v..the rest is burnt and can not read is better to put 9 volt zenner or 7.5..please advise. Thanks


HI Waleed,

In one of the hp 15″ lcd model the zener diode that always burnt was 7.5 volt. I’m not sure whether yours is the hp model.






Hi Jestine, I received your report, i read it but did not down load, my problem is i have an Emachines 17″ flat screen monitor, after some days o using, the power switch keep flashing blue and the screen is black, but the computor is still working because i can hear sound as i am playing music, I would like to know how to dismantle to check, Thank you, Ramdeo



For all lcd monitors open the cover from the bottom first (assuming you have remove all the screws and the base) with a flat metal. Once opened you can try open at the side of the cover. Check and make sure all e-caps are good  and that the outputvoltages from the smps are good and stable.





HI Shakawat,

Hello Mr. Jestine Young , I hope you well  . I saw your website , i like it , I want to learn the ,how to repair computer motherboard , monitor CRT and LCD , Hard Disk Controller , Dvd and Cd Rom ,Laptop , Printer Circuit Board .I also want to learn the UPS/IPS troubleshooting I know little things , that doesn’t cover or repair any electronics products , I have interest those fields , so how i began to learn step by step , pls advise me

You need to get this ebook Testing Electronic Components to start first.

Recently i have a problem in my 15 inch Samsung SyncMaster 550s monitor ,

the problem is : The monitor color is ok ,when it is running after few minutes it makes darks , after few minutes its ok , sometimes i press the monitor switch of and again press to on  , then its ok , Why this problem ? how can i repair this problem ,
pls give me the solution ,,

It is a dry joints in the crt board and you need to resolder it.






Dear sir,

I have one ITT ctv, the fault is when tv is started raster is normal but after two minutes as vertical ic heated, steady horizontal bars gradually comming up about three fourth of the screen. All other components appears to be ok, should i change the vertical ic (TDA1870A) or there may be other component faulty. Supply voltage is ok.

Thanking you

Gopal Sharma


Hi Gopal,

Change the vertical ic and check the surrounding components. Make sure the dc supply to the vertical ic is good and stable.





Hi Jonathon,

Hi Jestine I followed your Instructions carefully and with  A,B,C disconnected from the mainboard the LED blink was still there,

This mean the mainboard have problem.

so I put everything back like you said and began my tests On the Voltage Regulator with the 5 legs LM2596S-5.0 I am getting 12.18V DC in and 5.008V DC Out which I presume is ok,

Yes the voltage regulator is ok

the other 2 That you said to check to make sure they have not shorted, Im not a 100% what the pin out is to test them, also as they have 3 legs and there is no name on them ?

I believe both components are okay because you got the 5 volt steady output. I suspect it could be a 3.3 volt or 2.5 volt or even a 1.8 volt voltage regulator ic.

The small component you could not make out just says C614 just above it Is this a capacitor ?,

Yes it is a capacitor.

and if it is Jestine where would the inline fuse be as Ive hunted all over the mainboard for one,

In certain mainboard design the designer sometimes did not put in the fuse. It relies on the fuse in the power power pack.

and lastly could you give me the name of a good supplier for a MCU thats if I can still get one this board was purchased on 29/12/2002 but was £ 300.00 then which is expensive and its hardly been used,

Usually for MCU IC it is very hard to get from the market. Even if you can find one but is blank inside and need to be programmed. Sorry no source for this.

Thanks for all your help jestine as  I really do appreciate how hard it is to run a business and help people via E/mail it takes a good person to do this.

It is commitment and usually i spent at least 2 hours in just replying emails for my customers daily. Imagine if i go for holidays-ho-ho! Next week there will be 5 days repair course on and I only be able to support my customers at night.

Have a great weekend ahead.






HI Bailing,

Recently I do lots of UPS repair. Most of them replacing the batteries will do, but sometimes not. I hope you don’t mind answering UPS questions since it is also a kind of power supply.

This is another type of power supply which is different from the normal SMPS.

This UPS, after replacing the 2 12V 7.2A batteries, powering it on with plugging to the mains, the output voltage is normal ( 225 V AC ) but its buzzer alarm constantly ringing. If I unplug the mains supply, the output becomes 365V AC ( battery working ) and the buzzer alarm is still the same ( constantly ringing ). What could be the problem do you think? Will the output voltage go down to 220V if I give it a load, but I’m afraid to do it since the output with inverter working is to high.

For your information i did not venture into this type of UPS repair seriously because of the price of a new unit and the battery prices. Just like you we replaced the batteries and retest and if it is a APC UPS we might need to reprogram the eeprom ic as it can give all sort of problem. In your case, it could be the EEPROM IC problem. We never spend much time in troubleshooting UPS because generally the user will not pay for the repair cost. The reason for it was because after the replacement of the batteries, sometimes the main mosfet’s (which is quite expensive may give way).

By the way, for proper testing of UPS you need a load.






Hi jestine,i buy your e-book it is under my own name,but right now I’m not yet start my repairing the electronic equipment because now i`m still on duty in offshore but i feel so happy because i have a guide from your e-book thats can help me to solve the problem like TV,VCD player, DVD player and many others. so once again say thank you very-very much for your e-book thank`s a lot jestine god always bless you Amin….


From me


Ricky T
S`wak M`sia.




Hi Luis,

I recently purchased your book Testing Electronics, and I was so amassed to see how ease was to understand it.
I am just a beginner in electronics as a hobby.

Thanks for the support!

I recently purchased a Blue ESR meter but I am unable to use it, do not know how to read the graph/table. I am checking an e-cap 100uf (400 V) with ESR reading of .27  How do I transfer this number to the graph?.the Anatek manual for this meter is not explicit.   Could you help?.

I suggest that you use this link which is much easier to read:

In the link you did not see the 400 volt. However, you can make your own chart by adding the result you have tested. .27 ESR value is a good cap.





Hi Jestine

I have a lot of problem, I baught more than 40 portable DVD player to re-sell but the problem is most of them read disc error,no disc,should I replace lens or ?Can you give me an idea please? Somethime it keep turn the disc for long but no reading.


HI Lebrun,

Try check the spindle motor. A wrong speed could cause disc error.






HI Velt,

Hope your doing fine while reading my letter.

I’m fine thank you.

I have  question regarding crt monitor smps i have here a monitor with hissing sound heard at first i thought it is a high voltage leak coming from fbt but it not coz i try to hang the b+ at secondary output. but the sound still present it come from the power supply. now i start troubleshooting first i found 2 zener diode shorted and 1 ceramic cap. parallel at HER rectifier at 80 volts rail. after i replace that i test and its ok but after few hours the monitor will black out and when i open it and find out whats going on the same parts i mention above fails again. I think there is too much current in secondary side but i dont know what to do about that.Can you please give some pointers on how to solve this kind of trouble. And  what are the parts at primary side responsible in that kind of trouble. Also this kind of monitor smps dont have optocoupler ic and its using KA3824 controller, and lastly what is the function of the trimmer resistor i found near the controller ic can adjust this to lower the output. Thats all. Thanks in Advance Sir. And also sorry for my English…

I suggest that you visit this link to isolate the problem first:

and if possible replace with original part number. You may have to recheck all components in the power supply again. If you have the esr meter then it would be good. The trimmer is to control the total output power of the smps.

have a good day!





HI Noorishkandar,

Hello Justine…saya nak minta tips dari you.Sekarang saya sedang membaiki LCD Monitor jenama HP.Masalahnya  LCD Monitor Flickering When Powered Up.Boleh tak you beri sedikit tips bagaimana nak membaikinya?

Kamu kena check semua e-caps dgn esr meter. kadang kala backlight rosak pun boleh menyebabkan flickering.

Yang kedua saya sedang membaiki LCD Monitor jenama Acer.Masalahnya bila buka cover penutup belakang LCD tu dia ok tapi bila saya pasang semula cover penutup LCD tu display akan shutdown selepas 20 minit.

Saya cadangkan kamu check circuit track dan tengok samada hairline crack kat litar. Check juga dry joints dan e-caps.






HI Julianto,

I have 15″ crt monitor,when on and the monitor cable is not connected to
cpu, the monitor show “No Signal” message, with fine picture. But when I
connect it to cpu,the monitor is scrolling fast,from bottom to top,and the
picture also double in horisontal. Can you tell me the problem sir?

It may be the fault of bad cpu, bad horizontal/vertical oscillator ic or even eeprom ic. Use scope and check that the horizontal/vertical oscillator ic the vertical sync pin have waveform.

the second monitor,first,the problem is dead,I can repair it (thanks to
you),but after I connect to cpu, the horisontal is wide,I try to find the
pincushion circuit as you said in your report,but I cannot find it,I test
each and every FET that attach to a heatsink nearby flyback,but there’s only
modulation diode,the cap I check is find. I trace from the big IC that make
the voltage various as I press the horisontal size, I still can’t find any
bad component,the resistor check is okay.Can you give me any clue sir?

Did you find the pincushion transistor? I suggest that you check all components that connected to the modulation diode circuit.

the third monitor is 15″ crt samsung, the monitor is dead,when I try to turn
on, the led is on about 1 second and then dead. The voltage at the secondary
when the led on is normal,but when the led off it’s drop about a half.Check
the power FET is fine,check the transformer using blue ring tester is fine
also.Can you help me sir?

Try check the flyback using this link:

The fourth sir, the 17″ crt samsung is blur.I believe i’ts the flyback. If I
want to paralel the flyback, can I use a 15″ flyback? what I do is connect
the crt cable from two flyback,and use the focus and screen from 15″
flyback. I connect all pin (15″ flyback) to cold ground. Is that correct

Yes you can do that but some Monitor can’t modify that way because the 15″ flyback divider does not have capacitor in as compare to a 17″ flyback.

Why don’t you make the ebook about crt monitor sir,since the electronic
basic is all covered there,and also from your ebook you always make an
example from a crt monitor.

Sorry no time for that got to focus on the repair courses.






  1. John Smith

    June 23, 2010 at 10:08 am

    Hi Mr Yong,why fuse blown on crt monitor after press power button

  2. admin

    June 24, 2010 at 6:08 am

    Hi John,

    Many factors, shorted bridge rectifier or posistor. shorted power fet, power ic and even switch mode transformer.


  3. Edwin C. Anyasi Mr

    July 1, 2010 at 8:09 pm

    Hi Jestine I fixed a problem on a 29Inch LG switch. I 've to swarp switch from an older version grade 21' to the new flat screen 29' model as the later is not yet in market & behold de result was perfect & sound.

    I'm propossing a Business Trip to China if everything goes fine as per plans with
    my sponsor and, I 'll make a stop over at Malysia to meet with you. Off course
    i need an expertise advise from on Notebooks, PDA , Chinese mobile and Original mobile Phone . Cold you pls comment ........ Pls I need brakedown possibley on
    Plasma LCD and the current 3HD......?

  4. admin

    July 2, 2010 at 8:33 am

    HI Edwin,

    Nice to hear about that but I'm not into the equipment that you have mentioned. I'm more on the computer related equipment.


  5. kas

    January 21, 2011 at 9:00 am

    i have Samsung SyncMaster 550S going off after some time, when i pulged the switch in to the power board the monitor is on after 1 min monitor will turned off and not on after some time ,

  6. admin

    January 22, 2011 at 1:48 am

    Hi Kas,

    The flyback may be have problem. Please check this link:



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.