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Electronics Repair Questions/Answers and Testimonials- Part 74

By Jestine Yong on March 10, 2011

Hallo Mr Yong. I am very proud of you because with your monthly news letters
that you send to us I am now a better TV technician.
Have good day and God Bless you.

Regards
MJ in South Africa

=============================

A miracle happen today, I succesfully downloaded my copy of testing electronic components, Mr Yong I want to thank you and to tell every tech around the world that this is a must have, nothing like it and it answer all quections which all tech ask and probably end up not having answer. It realy worth it and I really know what to talk about without a doubt. Watch out Mr Yong because Muso is coming to be just like you.

Regards,

MUSO D.

==========================

Hello Jestine yong, I really have to say thanks to you. I fixed a power problem on a decoder power pack that was blowing fuss I guess it was plugged on a high voltage source, that coursed one of the power capacitors to bulge and a switching IC to be short circuited. it was from this months news letter that I read that made everything so simple for me, after reading through the audio repair I noticed the area where you talked about a short circuit IC so I quickly traced the voltage to the switching IC and I discovered that the IC was bad as soon as I changed it the power pack came up. thanks

Kingsley

==========================

Hello Sir Yong,

First of all I would like to say your e-books really fantastics……..

I discover your website while searching for electronic repair guide due to one of my tattoo power supply suddenly dead set after reseting the main power. Now i managed to pin down the slightly burned resistor which is the main problem (open), replaced it with new one and everything back to normal.

My Fashion is Tattooing, and your e-books really help me to solve my power supply problem. Now i still keep on reading it and hope to learn more about electronics.

God Bless you and best Regards,

Samuel

===========================

HI Roger,

Yes I have some question,can i substitute horizontal output transistor C5855 to C5149?

In fact you can try any hot that have 10 ampere and above and if the HOT run hot after a minute or so then you know it can’t be used. You have to try another number may be C5411.

How I can find ECG book in the website,thanks and regards roger

Try this link:

http://www.futurlec.com/BooksData.shtml

Jestine

===============================

Hi Jestine.

I just fixed a very nice set of Altec lancing speakers I was asking you about. I replaced 2 x 2200×16 volt caps and

also 2x470x16 volt caps. I did replace with Rubycons as

I always have luck with them and use them in all my LCD

monitors including some DVD player/burners that I have fixed with no power. And they work just as good as new

for customers. That is DVD players. Having lots of great

luck with LCD’s. I must have done at least 100 of them in the past 2 years. I learned never be afraid to tackle some

new experiences in life. And it usually works for me. Besides your book I have I am also learning a lot from You

Tube in Music and Computers.

God Bless You.

Gary

================================

HI Dave,

Thanks for all your newsletters. I appreciate them really as they always help widen my knowledge even if I’ve enocuntered such before there is always something new somewhere to learn. Thanks so very much.

You are welcome!

I av one little problem, there is friends laptop charger with me (hp 18.5v 3.5A), the problem is that it just stopped charging the laptop. I tried another with the laptop and it worked fine; also i tried the charger on another laptop and dstill did not work, but one thing that now surprised me is that when i tested the output of the charger with my meter, it showed the 19V complete but did not charge any system. When I even opened it, there was no physical sign of damage and testing things I can easily test, they are all working fine. Please, what could be the problem?

Try check the filter capacitor with ESR meter and in certain model power adapter, there are 3 wires in it and if one of the wire broken, the laptop will not be charged.

Another case is another charger like that also same rating, on opening discovered the capacitor was damaged and then tested other components, they work fine but on replacing the capacitor with the same type, it just became very hot and swoll up immediately it was plugged into power and also got damaged. What could the problem of this also be?
Thanks always taking time to answer even personal questions. Looking forward.

It could be bad quality cap or the output voltage is too high that have destroyed the capacitor. You may need to check the feedback circuit especially resistor in the secondary side of optoisolator ic.

Jestine

=========================

HI G,

I am a radio technesion who engage in repairing of radio and
monochrome color TVs.

Noted and nice to know you.

I have two problem with two colour Tvs which I have received recently
for repairing.

1) problem- LG colour 20″ TV model no CA20D16
sound and snow(raster) ok. sometimes, picture is OK,sometimes picture
disappired and it remains like slanting patten moving both
horizontally and vertically.sometimes when picture is disappered
mentioned above then,screen becomes little bit smaller just by 01
centimetire from four sides.as it appers no colour problem with the
picture.checked allmost all components except fly back.

main components are as follows:-
IC-TDA8362
IC-LG8634-17D
IC-STR S5705
IC-LA7222
IC-TDA4665
TR-2SD5220

If you have the photo then it will be good to see the problem. I suggest that you check all the output voltages from the power supply and make sure all are stable and good. Try gently knock on the pcb board with the plastic handle of your screw driver to see if there is any dry joint or not.

2) problem-NEC 20″ colour TV model no FS-2181PBNC
at the time I received it had problem sound OK no raster just only
horizontal line was appered.when I tried to check vertical output side
then, the IC no STK 730-080 in power supply was suddenly burned
out.then, checked almost all components in power supply section.after
that,replace with a same type new IC and tested circuit again.it was
realized that new IC too, was spoiled again.there after, replaced two
more ICs but all spoiled within short times as usual.

main components are as follows:-
IC-M34300-532SP
IC-M51408SP
IC-NJM2245L
IC-TDA1905
IC-M6M80011AL
IC-STK 730–080
IC-LA7950
IC-AN5515

those are the faulty symptoms and main parts of two faulty TVS.
actually,this has been a big problem for my carriear.

I suggest that you visit this the link below to isolate the problem first. Make sure all the output voltages are good and stable before moving on to check on the vertical ic area:

http://www.scribd.com/doc/2957819/TT204-Identifying-television-SMPS-problems

Jestine

=====================

HI Bailing,

This CRT monitor has very strange symptom. I had connected the input signal with signal generator first and then turn on the set, and the display is like the video attached.

When it displays white ( expected to be same with the signal generator ), there is still written “input signal disconnected” and then blank ( black display ) for a moment and then the white display comes again for a moment, after a few cycle it stops with standby mode ( input signal still connected with genearator ). When the display is white, G1 is -65V, when the display is blank ( black ) the G1 is -205V

I had checked all the vga cables to be OK. Is this the cpu problem, what do you think?

Most likely is the cpu problem. If the cpu part number start with WT8045 xxx then chances is high the cpu have problem. You can use your scope and check for the output waveform of h/v. If you did not get a good waveform then replace the cpu.

Jestine

=================================

I have 3 CRT TV – Sharp, Sony and Panasonic. All got the same problem – Bad tube. Sharp & Sony problem picture goes to purple color (no green driver) and Panasonic problem dark picture. what can i do for the Bad tube? can i repair it? or just throw away.

Hi ,

I suggest that you follow this link to try to save it first before throwing it away:

http://www.repairfaq.org/samnew/tvfaq/tvbrightcrt.htm

Jestine

==============================

Hi Bailing,

Does pincushion transistor always use heat sink?

Yes

I have checked all transistors with heat sinks to be OK ( off board testing ), but I found that h&V yoke coil only lit 2-3 leds tested with Blue ring tester.

It is in the marginal result because bigger picture tube tends to have lesser LED light up.

Could this be the cause of not being able to adjust the horizontal width?

If the HOT is not hot then is not the tube problem. Usually if the horizontal yoke coil shorted you will not be able to adjust the width and the HOT will become very hot. Eeprom data corrupted also could cause display width problem.

If you have locate the pin cushion transistor the collector should have voltage and it can be varied when you change the width in the osd.

Jestine

==============================

the CRT brightener was a common item (sold in every corner drugstore, it seemed!).

What is it?

It is a device to brighten up picture tube but nowadays no longer selling in the market. It is a device that boost the 6.3 volt to about 9 volt

Voltage for the CRT filament is usually obtained from a couple of turns on the flyback transformer. It is usually easy to add an extra turn or two which will increase the voltage and thus the current making the filaments run hotter. This will also shorten the CRT life – perhaps rather drastically. However, if the TV or monitor was headed for the dumpster anyhow, you have nothing to lose.

Still don’t know how to do this, need further explain….in Malay can??

Maksudnya, kamu kena menggunakan dawai halus (dawai speaker ) untuk membuat beberapa lilitan dekat flyback core untuk mendapatkan voltan yang tinggi (melebihi 6.3 volt). Akan tetapi, cara ini akan menyebabkan janka hayat pc tube lebih pendek.

Jestine

==========================

HI Catalino,

Good am sir! Thank you so much for the some article you send to me every month, this is very important to me.

You are welcome!

Sir can I ask some question using only e-mail? This is an effort to you but I can understand if you can’t reply with this. Sir how will i know the burnt resistor value, diode without number or code, ic’s, transistor that the code was fade because of break without any schematic diagram? I know that you have a book all of these, if you cant answer some of those, can you please share me some information about how to know burnt resistor value. Thank you sir I hope you can understand. Sir I want you to know that electronics is my ambition in life. I consider you as my teacher.

It will be tough to identify those parts without a schematic diagram. There are only few possible way:

1) visit forum and ask (some repairer may have this model in their repair bench)

2) call up your repair friend to see if they have any of the similar model in their work place

3) through experience. If you know the circuit well enough you can at least try on error to put in a substitute part.

4) buy from ebay the broken set that is similar with your model. Open it up and compare.

Jestine

==============================

Hi, Jestine

I am enjoying your book and the periodic articles you write. I wonder if you can take a moment and direct me as to where I could find a data sheet for a transistor that I recently checked from a circuit. The housing is a “regular” small plastic housing, I think it’s TO92.
The writing on the side of the item is: Top Line = 9015
Second line= C:415
Third Line = EBC (designating the leads as emitter, base, and collector)
I have searched the internet but cannot find a cross reference for this part. It checks as an NPN transistor. It is more of a signal type, than a power type. However, all my searches for items which I believe would be similar, such as 2sc415, come up power transistors, and the description does not match this part. I’m not sure how to figure in the first line: 9015. It does not seem to yield any meaningful results in my search.

Thanks again for any assistance and guidance. I look forward to hearing from you.

Steve

Hi Steve,

You are welcome. Try this link:

http://html.alldatasheet.com/html-pdf/329861/KEC/KTC9015A/55/1/KTC9015A.html

Jestine

=========================

I absolutely love your book.

I can’t wait to finish reading it.

I can’t wait to get an oscilliscope, smart tweezers, and atlas component analyzer.

I’m sure I can figure out how to use them using your techniques.

Thank you so much for publishing your work.

All I can say is, I can’t wait to purchase your entire library of books.

Clinton Y

=====================

From Richard,

Anyway so much for that, now that i have the blue esr i need your help i’m kinda confuse, i removed 6 bulging caps out of 9 (6.3v 1800 ufd) i stopped removing the rest casue i’m wating for the blue esr, i measure the 6 bad caps and the reading is 2.0 to 3.0 ohms and i measured the brand new cap (15 pcs) its .00 to .01 ohms but when i measure the rest of the bad cap(picture bad caps attach) still in the motherboard it was .00 ohms kindly explain to me how to read the BLUE ESR ? Heres the caps i measured:

Busted 6 pcs 6.3v 1800 ufd= 2.0 -3.3 ohms

New 15 pcs 6.3v 1800 ufd= .00 – .01 ohms

New 3pcs 6.3v 820 ufd= .02 – .03 ohms

New 4pcs 16v 1000 ufd= .01 ohms
Since its more than 500 ufd, ON ESR ohms scale and Capacitor Rated Voltage scale starts at 10 where do the values fall into the graph is it under the >500 ufd between .01 to .0 ohms? But Capacitor Rated Voltage starts at 10.

Heres another one:

New 1 pcs 50v 10 ufd readings is 1.9 ohms so i’m supposed to be looking at 10 ohms that has 5-10 or 10-100 ufd and the voltage should be in between 35v and 63v right?

and the last one:

New 1 pc 50v 2.5 ufd reading is 2.6 ohms i should be looking on ESR ohms between 10 to 100 ohms that has <5 ufd and Capacitor Rated Voltage between 35 to 63 v if thats the case the capacitor is bad? or im reading the Blue ESR the wrong way so please help and thank you in advance.

You could use this link to compare the result as it is much easier to read than the graph.

https://www.jestineyong.com/?p=1314

For your information certain bulged cap have a good reading because the internal section of the cap is not affected yet thus you will measure a good reading. As a rule of thumb, if you see any bulged cap (even a slight bulge) just direct and retest the board.

If you have other question please do email me again.

Jestine

===========================

Hi Jestine,

Thanks for the link. I think that I came across this part on another site, but I thought the part tested as an NPN transistor; this one is a PNP. I went back to your book and rechecked the part and yes, it’s a PNP. How does one know which numbers to check? On the part, there is the 9015 and the C:415. I was thinking that the C would translate to a 2SC transistor part number. How does one know which of the numbers is significant??

Thanks again for your help,

Steve

HI Steve,

Actually there are many manufacturer who do not follow international standard. Since the current NPN (2sc) number is only till 6xxx thus 9015 is too high. Besides, the manufacturer have removed the KT leaving behind C9015. Thus in the future if you come across any number that is too high try place KTC in the search.

Jestine

=============================

Not mother boards but lcd pc board..I customer broght an lcd screen and there is a burn in the board..I replaced the diode..I am just wondering if that burn spot can be covered with something..or what is the best way to fix it.

HI Waleed,

Usually i do not cover if there is a burnt hole in the board. I will scrap the hole surrounding area (make sure there is no connection because the burnt carbonized thing could conduct) with a pen knife and clean it with Thinner.

Jestine

=======================

I would like to know what to do with a laptop that dropped water on it. It does not start at all. I left it to dry and after 3 days I tried to switch it on but without luck. I cannot see even the power led on when I connect the adapter.

What can I measure on M/B and how can I be sure of what exactly is the problem?

HI Chris,

Actually you can use a hair dryer to make it dry first. If there is still water in it and power on the board could develop short circuit. Make sure the voltage regulator circuit is functioning first before checking on the main board.

Jestine

=======================

With the help from you personally and your article on testing electronics components, I was able to rectify the fault on the circuit mentioned before.

Please thanks for your much needed aid. I appreciate; your articles are worth buying.

Solomon A.

======================

I have a problem with my lg 500g monitor The MOSFET 10N20C overheat
and HOT(J6810) to blow off .After replacement the HOT(J6810) blows
again and there is a ticking noise from the power supply.

HI Das,

Try visit these links:

http://www.electronicrepairguide.com/testing-flyback-transformer.html

and

https://www.jestineyong.com/?p=403

Jestine

========================

believe or not with only your demo eBook I’ve repaired my lcd 19″ monitor…

i think i’ll buy your book… it should be a good investment…

thankyou.

antonio – italy.

=====================

HI Willem,

Can you please help me. Where is the Pin-cushion circuit on a TV PC Board.

Usually near to the flyback and the pincushion transistor is attached to a heatsink.

I have a problem with a tv and the fault is within the Pin-cushion circuit according to a book I have and internet sites. I am attaching a photo of the faulty display. The picture is bowing in at both sides of the screen. Could this IC LC863328B that has Vertical and Horizontal synchronization signal input terminals be faulty.

Well, it can be that ic problem but replace it at the last resort

Am I wright to think that there is a synchronization problem.

The synchronization is okay because you got a steady picture.

I tested all the transistors, caps, diodes and resistor in the power supply side

Pincushion problem is nothing to do with power supply because you already got a nice picture except that it is curved.

as well as the Vertical and Horizontal circuits and apart from a damping diode RU4DS and a 10MFD, 25V. Everything else tested good. The original fault was that the TV stayed in stanby with LED on. By replacing the diode the tv came on but now the picture is bowed in.

Make sure the B+ voltage is enough (a lower B+ voltage could cause it to curve inward) and that the pincushion transistor center pin have voltage and this voltage will vary when you press on the horizontal width/pincushion control in the OSD.

Jestine

==========================

good day mr jestine,
does it possible to replace crystal 32.768 mHZ with 4.433619 mHZ?
thanks a lot!

HI Boy,

Crystal has to be replaced with the same type otherwise the system will not work and sometimes hang.

Jestine

==============================

Ok..tak mengapa dan terima kasih kerana cuba membantu.Saya dah send tv plasma tu ke samsung service centre.Yang kedua saya sedang membaiki tv brand panasonic 21 inci yang problem nya display kabur.Setelah saya tukar crt connector dia ok tapi masalah keduanya output av tak berfungsi.Apabila saya pasang dvd tiada apa2 keluar di screen tv.Kebiasaannya ada satu ic berhampiran av output tu yang rosak tetapi untuk tv panasonic 21 inci ini ic tersebut tiada.Apakah av output ni dikawal oleh ic controller yang besar itu ataupun ic yang kecil sedikit yang berhampiran dengan suis preset untuk volume,channel?

K..terima kasih,
Noorishkandar

Hi Noorishkandar,

Anda kena trace dari av output litar ke puncanya. Sekiranya ia datang dari IC controller tersebut make anda terpaksa tukar dan retest tv. Kalau anda ada scope maka ia akan menjadi senang untuk trace kat mana hilangnya audio signal.

Jestine

========================

Hi jestine

Thanks the zerner tester instructions . It is a really useful aset in the drawer. Here i attach some pictures of the unit that i recently buildt.

I have learned a lot from your power supply repair book, i enjoyed reading it and now smps is not so complicated. Troubleshooting now is much easier.

I like the way you explain everything step by step.

Sincerely

Julian C.

=========================

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11 Comments

Thomas

March 10, 2011 at 2:50 pm

Hi Jestine,

Simply Question about SG6840 PWM Controller, on Pin 7, must the VDD Voltage measurable BEFORE the PWM starts or AFTER and even the PWM is defective ?
I only have 1.7 Volts on this Pin, its an external TFT SMPS with no Power failure, i checked everything and changed many parts like Caps and the MOSFET(on the Middle Pin 320V) Bridge Rectifier and Cap is working.
Where get the PWM VDD Pin the Voltage ?

Thanks,
Thomas

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admin

March 12, 2011 at 2:15 am

HI Thomas,

The VDD should have about 20v (according to the ic spec) when you turn on the equipment. If you are getting only i.7 volt this mean either the ic itself have problem or the corresponding component is bad. Try get the part from the below link:

http://www.utsource.net/sg6840.html

Jestine

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Daniel F

March 20, 2011 at 7:29 pm

Hi Jestine,

I've finally installed your rss feed into my mail client so I can read all your posts at a glance.
Thanks for introducing that feature.

Anyway, I have a query.
I am repairing a dell 17" lcd computer monitor which won't power on after a power cut, no leds light.
I'm certain the fault is a tiny electrolytic somewhere in the startup circuit. I've attached a photo for reference. The 1506IC I have circled is a Buck DC-DC Step Down converter;

http://pcserv.org.uk/images/dell17.jpg

http://www.diodes.com/datasheets/AP1506.pdf

I can sometimes trigger the monitor to start up (turn on) if I use my multimeter on DC to probe the pins of the 1506IC or surrounding area. The charge in the multimeter probes must be initiating the startup circuit which leads me to think this circuit has some weak electrolytic somewhere. When the monitor is off, there is 12v on the vcc pin of the 1506IC which is correct, but there is nothing on the output pin (normally 5v) or feedback pin (normally 1.2v). However when I trigger the monitor to come on, everything works fine.

With your advice I purchased the Blue ESR and RING tester. So I used the ESR tester but couldn't find any bad caps at all. I also checked every component possible around the primary/secondary circuits and found nothing wrong. I have access to a 100MHz scope so my question is; is it possible to trace weak / problematic components with a scope? Is is possible that they will show some reading as they try to start?

Thanks for your time Jestine, I very much appreciate you taking time to answer everyones questions.

Regards
Daniel

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admin

March 22, 2011 at 9:19 am

HI Daniel,

Thanks for the photo. If all the corresponding components are tested ok then you need to direct replace and retest the set. The ic inside have lots of components and it could be the components inside the ic that cause the problem. As for the scope you need a similar working machine to compare the waveform. By just measuring the points in the circuit one would not know if the component is weak unless you really have experiences in troubleshooting this model many times.

Jestine

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Emmanuel N

March 23, 2011 at 3:01 pm

I have bought your books on repairs and they are wonderful. I am fixing a PS3 sony computer entertainment, on the power supply board I replaced to burn down electrolytic capacitor of value 420V, 130uF with 400V, 100uF. I was able to measure about 320V across the capacitor when plug to the power supply but am not getting and out to PS circuit control board. Please can you help me with out.

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admin

March 24, 2011 at 9:18 am

HI Emmanuel,

Did you check all the components in the power side? Have you replace the power IC and retest?

Jestine

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Daniel F

March 25, 2011 at 10:54 am

Update: Regarding my post about the 17" Dell monitor above;

Hi Jestine,
For your information the AP1506 was acting unusual so I replaced it with the AP1506 from DIODES INC. and it has fixed the problem. 24 hours burn-in and it still okay so I guess the lesson here is sometimes you should go with your instinct.

Thanks again.
Daniel

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admin

March 25, 2011 at 10:54 pm

Hi Daniel,

Congratulation!

Jestine

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othman

January 24, 2013 at 7:45 pm

Saya menghadapi masaalah tv samsung plasma 42inc yang tidak mengeluarkan gambar dan suara.Mohon En jestine membantu saya

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- Jestine Yong
  
  January 25, 2013 at 10:22 am
  
  Hi Othman,
  
  Ada power tak? Kamu dah check samada voltan kat output SMPS?
  
  Jestine
  
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  Reply
ALABI

March 1, 2019 at 8:41 pm

Please sir, my strong decoder srt 4675 is not detecting signal. The signal level just remain at 37% not responding.pls what could be the problem?

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