Hello Jestine,
Well my teacher, you won’t believe this.
I finally have learned how to test a mosfet!!
It does not go to the center of the meter as you wrote in this article but it does move toward the center and stays there “on” after touching the gate and drain with my finger. After I have touched the gate for a second and go back to the source it is now “off”.
I have also found a mosfet that never turned “off” after touching the gate. It stayed “on”.
Thank you so very much for showing me this trick and to think that I accomplished this test with the cheapest meter (You recommended it) makes this all the more memorable.

Thank you again Jestine,



Thanks a million! I could download the SMPS repair ebook and what I have read so far is absolutely impressing.




Hi jestine


Oh oh jestine how can I tell you about your amazing smps repairing and all your E-books. all my headache have been cured (doctors) electronics can I say? I am realy excited the way you laid the book out was great it is packed with great information thank you so much for all your efort you have done for this book need time to read  there is no any books

like this!!!!!!!!

Thank you Jestine

I wish all the best to all



Hello! Mr. Jestine Yong,

It’s been quite some time now.

I am one of your e-students. I’ve bought virtually all your books. I have read them and I am  on my own now and I thank you for the advice you gave me on starting the business.

I’ve never had any regret for taking the decision


Thank you Sir.



Hi Jestine,

i have just finished my first work on a 21 “Philips CRT TV which could not even come on after it blow the 4A fuse.i found a capacitor 47uF 250v had a problm giving 5uF (using capacitance meter on DMM) and -open ESR measurement using BLUE ESR.which i replaced with a new capacitor with same specifications.

Iam Haappy




please tell me how can i test  40 mhz crystal.my crystal tester is good up to 35 mhz only

HI Beh,

Since your tester only could test until 35 mhz then i guess you may need a oscilloscope to test it. You need to power on the equipment and test the crystal.




Thanks for the newsletter
need hints on repair of Mercer CRT monitor
no circuit diagram no control on pincushion and width mo circuit diagram
Any help

Thanks and best wishes

HI Humphrey,
Pincushion and width usually are related. It can be caused by lack of B+ voltage, shorted modulation diode and related circuitry or even shorted in pincushion transistor. Sometimes a bad eeprom data also could cause such problem. I suggest that you make sure the B+ voltage is good and then make sure the center pin of pincushion transistor have dc voltage.



Hi Jestine:

In this case my PC stopped working one day.  When I opened it up I saw some electrolytics on the motherboard that had vented.  I replaced those, but just in case I checked the ATX PSU and found that the 5vsb line was only putting out 2.9v.  I replaced it and the PC works ok now but I wanted to repair the original PSU in case I need it again.  I opened it up and all looks ok except for perhaps two electrolytics that look they are on the way to failure (bulging).  I could just replace them but I would rather be able to do some intelligent debugging – nearly impossible to do without a schematic.


HI Bill,

Noted. The problem is many repair tech have uploaded many consumer electronics circuit diagram except the ATX. Try this link to see if will help you or not:





HI Kushan,

Dear Mr Yong;

Thanks for the newsletter. i found following problems when i troubleshoot a monitor. can you please tell me ….

  1. How to identify a primary side of a FLYBACK ? (only a FBT which has removed from the board).

Trace from the B+ supply input and the collector pin of HOT.

  1. I have a SAMPO flyback of a 17’ IBM monitor. But I couldn’t find any t technical information on it from the internet. Do you know how to find a sillier one ?

Sorry no info on this-try http://www.hrdiemen.es

  1. are there any data-sheet sites for FBT on the internet ( such as for semiconductor- datasheet) ?

Try http://www.hrdiemen.es




Hi Bonolo,

4 volt seems to be low. It has to be 5 volt. Try tracing backward to see if there is any component faulty in the 5 volt line. It can be bad filter cap, leaky diode and ectc.



Hi, Justine


My Instructor i would like to bring to your attension it is in respect of HP vs19e LCD Monitor

it was brought in dead with power led (blue) brink continouisly.The fault tune out to be

two capacitors namely 10v/1000uf i found them  high in value.

I have replaced the above components and the Lcd Monitor is able to start up normaly but the all LCD PANEL is flashing starting with red colour green, blue,purple and other coluors

then it start again with the same colour red.

what could be the fault is it the LCD Panel or something to do with mother board.

thank you.


Hi Simon,

Check the signal cable and make sure the H/V signal is connected. Check also for components from the vga connector to the MCU in the mainboard. Sometimes it can be components shorted around that trace. If all check to be good then suspect a bad MCU in the mainboard.



HI Boling,

Today I have solved one of the ATX which had lowest 12V rail ( 10.7V ). It was the dual ultrafast diode which has a hairline crack, see the attached picture.

I found the culprit by chance.First I doubt the dual big filter capacitor 330uF 200V to have lower capacitance, and yes testing it with my Atlas LCR meter it only measured 224uF and then I replace both e-caps with genuine rubycon which surely has more accurate capacitance and switching it on. Guess, what happened? The ATX 12V rail was dead ( the fan didn’t turn ), and I checked and found the dual ultrafast diode punctured ( the analogue pointer moved both ways ), after taking it out I saw the hairline crack and after replacing it, now the 12V rail is 12.2V.

About the other ATX, I also used the “replacing the dual big filter capacitor with genuine rubycon” and the unexpected result was one of secondary e-caps rated 1000uF 16V blown ( like you put it reverse polarity ). Replacing the e-cap with good one solved the problem. Actually I had checked this culprit e-cap with ESR meter and the result was good, could be the 16 voltage limit is lower than it should be. This is another lesson for me to use the best capacitor when repairing ATX power supplies. Eventually this other ATX 12V rail only has 11.8 V after replacing the culprit e-cap, but loading it either with a hard disk or real full load, found no problem. Also attached is the photo of genuine rubycon 330uF 200V and the blown 1000uf 16V e-cap.

What a good try-you are the fantastic! Now in the future if there is any atx power supply with low output voltage you will surely solve it within minutes.



Thanks alot.Plz one question 4u.What would happen if i used an
external 12v 100ha on a uninterupted power supply instead of the
normal 12v 7ha

HI Nicholas,

I have not try that before but have i have tried slightly bigger ah like 12 v 11ah.



I have an crt monitor red color lost brand edl ifed up to try to find solution


CRT monitor lost colour could be caused by broken red signal cable and bad components or even dry joints in the crt board. I suggest that you perform the voltage and signal test between the R and the G,B circuit. Any different is the clue for you to troubleshooting at that area.



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