To,
Mr Jestine Yong

Well it is a great honour of being given a chance to be one of your students because you are really great not in the sense of a businessman but a great teacher. I have seen a lot of businessman and many more bosses around the Malaysia and even in Singapore but not like you alone. You have proven to be a honourable man because your education and teachings brings up my  carrier too. Not only me but to those all who follows on your track, too manys to say ……….I believe if i have got a chance to come up to be a businessman in my live again, i will definately do something for you. Why i have to say this because, in this world there could be hardly we can see anyone who is willing to share their education nor wealth but sir you have proven. Well i’m really glad to view your message because i feel that my skills and knowledge is growing. Have a nice day.

Thank you

Your Sincerely,

-Andrew-

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Hi Jestine,

Our church amplifier got its big main capacitors blown, because unexpectedly the main line voltage became 380V AC!

Now the electrolyte has spread all over the boards ( please see the attached photo ). Will the liquid cause any bad effect to the circuit board? Do you think the pcb can be cleaned and how to?

Happy teaching and have a great weekend,

Boling

Hi Boling,

Thanks. Don’t turn on the set if the liquid is still on the board. You can clean the board with thinner. Check all surrounding components and make sure no other bad components before you turn it on again. Check also the other 3 filter capacitors.

Look for the 240 vac outlet before turning on the set.

Jestine

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Jestine i need enlighment,what is the difference between a service and training manuals?

Hi Michael,

Service manual is more on the schematic, parts list and some basic info about the equipment. Training manual means it is more on indepth of that equipment. The content could be touching on how each particular section work, the voltage and waveform signal, how to troubleshoot and many more.

Jestine

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

hello sir YONG, i have been trying to find 2SA1296 but not yet. have you come across this transistor? or may you help me with replacements thanks subscriber

Hi,
According to my databook the equivalent number are : 2SA1315,2SA1382,2SB985 and 2SB911

Jestine

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

Many thanks to you all my friends,for always email me even w/o my 2months reply,due to the damaged of my computer.I almost drops my tears of happiness when  i read your email…thank you for your continued support,brothers; i;m alive now, so lets go on..mario…

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

Hi Bashar,

If you measure base (black probe) and collector (red probe)
it should have reading.
-If you measure base (black probe) and emitter (red probe) it should have
reading.
-If you measure collector (black probe) and base (red probe) it
should have no reading.
-If you measure collector (black probe) and emitter (red probe) it
should have no reading.
-If you measure emitter (black probe) and base (red probe) it should have
reading.
-If you measure emitter (black probe) and collector (red probe) it should
have reading.

The above test is for Horizontal output transistor that have a built in damper diode.Since  C5411 does not have a damper diode then :

-If you measure emitter (black probe) and base (red probe) it should have no
reading.
-If you measure emitter (black probe) and collector (red probe) it should
have no reading.

ANY  SUGGESTIONS  ABOUT MONITOR PROBLEM WILL BE GLAD >>>SO SORRY FOR LONG MESSAGE

Orange LED means either the h/v signal from the computer is not reaching the monitor CPU or the monitor CPU and eeprom data could have problem. Make sure the CPU and eeprom ic are getting 5 volt. and the CPU crystal have sinewave. 

AGAIN YOUR BOOK IS MORE VALUABLE AND HELP ME MUCH BEFORE TO FIXING MONITOR PROBLEMS

Thanks.

Jestine
http://www.JestineYong.com

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Hi justine
i have a TV , when you switch it on . the red LED lit then after that nothing happane no sound no picture
thanks THAMI

HI Thami,

Most probably is the mainboard. If the CPU did not send out the on signal to a relay or opto ic then the main power supply will not be turned on. In other words, if the opto circuit, cpu or the eeprom ic have problem it will be in standby mode. First you need to check if the mainboard is getting good voltages or not.

Jestine

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

HI Waleed,

there is 5 volts going to the main board and suppose to split into 2.5 and 3.3 volts right?

yes you are right.

I found AS1117 faulty. there are two voltage regulaters on that board. one is getting five volts and getting out 3.3 and the other regulater is getting out 1.7. the strange thing is, the second regualter suppose to get five volts to regualter but instead there is on the out leg 1.7 and the ground leg I can read 3.3. is that strange?

Some model will have the 3.3 volt to power up the 1.8 volt voltage regulator. Since you are getting 1.7 volt I suggest that you replace it and retest. You can test those voltage regulator using an external dc power supply. For your info output pin is different from the 78 series voltage regulator ic.

Jestine

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

I directly replace the capacitors and check the Vout without a load.
the voltage reading was 24 volts and then it slowly drops into
0volts.
what would probably the cause of this decreasing voltage?

Thanks,
Raynald

Hi Raynald,

You need a load because without load the smps will shutdown. That’s why the voltage slowly decreasing.

Jestine

======================================
Hi jestine,

You’re electronics genius, I’m so amazed on your skill!

I hope you can help me again, I presently repairing a LG Flatron L1710 17″ LCD Monitor, this is quite old but I just want to know what is the caused of this problem just in case I will encounter again this symptom, when I turn on the monitor there’s a randomly horinzontal lines, it goes up and down on the screen, I think they called it flickering, I opened the monitor and I did not see any bloated e caps either in power supply and vga board section, do you have any idea on how this problem is happened?

Thanks and more power to you!

Dexter

Hi Dexter,
Check if there is any dry joints in the vertical IC. The IC is attached to a heatsink and should have about 7 to 9 pins.

Jestine

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Hi Jestine,
Brother i need to ask you something that is about Solder Gun how to choose solder gun ?
Which solder gun would be appropriate and please mention soldering iron as well Rosin core or acid core?.

Kindly

Bilal

Hi Bilal,

It depends on individual. Mine is hakko 981 dual mode solder gun. You can buy a normal 20 to 25 watt solder gun. the solder lead I’m using is 0.8mm with 60 tin and 40% lead or we just call it as 60/40.

Jestine

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

Voltage regulator kia78r09api

It has four legs 1 input 2 output 3 ground 4 on/ off control. Does the on/ off need to function to get the output. It is in secondary side of ps supply of lg tv. It has an input of 9 volts something and no output. The led is on red.

 

Hi Zed,

Yes the control pin needs a signal  (usually from the cpu/mcu) to turn on the voltage regulator so that it could have output voltage.

Jestine

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Jestine,

 

No, it’s not working yet. I mean I will try to replace the whole main board with a spare since smd components is not available here in our electronic store. By the way, I replaced the main board last night from a non working lcd with the same model. But this time, the monitor flashes the rgb color. I mean, after one second the whole screen will diplay red. After that it will display green and then blue.  I have compared the voltages of the regulator and this is what I got. On the old main board, I got 3 volts on pin 1 and 2 volts on pin 3 with no voltage at the vcc of the inverter IC. On the second board I got 3 on pin 1 and 0 on pin 3 but there is 14 volts at the vcc pin of the inverter.

Do you have any idea on this? Thanks…

 

Randy

Hi Randy,

In some lcd monitor, if you did not connect the vga cable the disply will turn red, green and blue. Try also check for any broken h/v signal wire inside the vga cable.

jestine

Hi Sir Jestine,

I replaced the vga cable with new one. The lcd already had a display. Only, when I turned off the cpu and let the lcd monitor on, the rgb colors still flash one at a time. Well, the lcd is ok right now and I can use it as of now. Sir Jestine thank you very very much. Your such a good teacher. Thank you very much….

Randy

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iqbal
Subject: hi jestin

how r u,im iqbal from fiji i like reading ur repair book, jestin u cant belive before reading this book i dont know anything about electronic repair but after reading your repair book,now i become a electronic technician thanks alot sir,may god bless u n ur family,

from ur fan iqbal.

==========================================
jestine,my acer lcd monitor has just malfunctioned, while before it was working properly. my complaint with the monitor is that…if i switch it “on”,what i could see is the acer logo for a second,,,,then black out screen”. i tried to search this problem to your website and you have commented there that the likely cause of this problem is..a defective transistor C5707, which i carefully traced it…and i really found out 1 of the 4- C5707 transistor was bad. since only 1 was bad, i changed also the 2nd transistor being a pair component….but unfortunately…the problem is still the same.hu-hu-hu!!!!for the meantime, i bought a new monitor, a LED type…to replace that defective acer monitor.i would appreciate any assistance you could further extend to me regarding this “trouble.”(as i have no esr meter to check caps. i just used my dmm to check those caps involved, and seemed to me they are all OK; no open/shorted indications}

Hi Agapito,

You also need to check for dry joints in high voltage transformer and make sure the tuning capacitors are good. If not once you turn it on the c5707 will blow again.

Jestine

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Hi Jestine Yong, tnx for sharing your knowledge about electronic repair… especially to us ordinary people, I am so grateful to you for all the lessons and tutorials that I’ve learned from you. I can now be able to repair LCD Monitor without any fear of breaking it unlike before.

Winston.

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

Hi,
what is the ways to study an IC and discover what voltages and frequencies to expect in each of its legs.

Regards

Shehab Ebrahim

Hi,

Download the IC schematic and understand the function and the pinouts.

Jestine

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

Hi Jestine

Hope you are well. In a ATX smps, all voltages are ok, instead of that i am not getting PG 5v. I have replaced LM339 also and there is no bulged capacitor. To get PG voltage, all other voltages are how much tolerable. (+5, +12, -5, -12, 3.3).

Regards

Gopal Sharma

Hi Gopal,

Check if the main filter cap in primary side have problem or not. Sometimes if one of the main caps have problem there will be no PG. Check also components surrounding the LM339 because if a resistor or cap problem it could also cause similar fault.

Jestine

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Dear Jestine.

How are you.i am fine.i need small help from you.i have a LG Model
:21FC.RGE TV that one FBT is defective.problem is FBT part numberplate
is missing.so how i can find correct FBT for that TV.PL help.have nice
day for you.

Best Regrds.
Manjula.

Hi Manjula,
You need to find the schematic diagram/service manual that have part listing. Or you can check with your LG distributor in your country.

Jestine

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

Hi Lito,

i just wanted to ask how can i easily identify on crt monitor and tv the B+ terminal on flyback transformer?

To find the B+ voltage trace from the power supply. The highest voltage is the B+ line and see which flyback pin it goes. 

..and also how am i easily identify the primary of flyback transformer?…

Once you found the B+ pin of flyback then the other pin is the horizontal output transistor collector pin. If you test with blue ring tester the LEDs will lighted up.

Jestine

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

Hello Jestine,

This is Misael, I am constantly getting email from you regarding updates on ELECTRONICS REPAIR.  I really appreciate this emails from you.

I have a background in electronics since I am an undergraduate of Computer Science and my major is in computer hardware.

I am writing you this letter because I really need your help, I want to start my own small electronic repair shop here in Manila, Philippines, and since I was not able to practice much of my discipline,

I would like to humbly ask for your opinion on how I can start re-learning again how to repair electronic equipments such as PC, Monitors, Printer, etc.

Please help me since this is all that I know to be able to do to earn a living.  Thank you very much.

regards,

Misael

Hi Misael,

You must first know the safety and accurately test electronics components. Once you are good in testing electronic components then you need to know what repair field you wants to be in. If you like LCD Monitor repair then get the LCD Monitor repair ebook that comes with the author support. If you like LCD TV repair then get LCD TV repair ebook and etc.

Jestine

===================================
Hi Jestine, I need your help once more. I have a power supply board the has a 220 Volts AC supply and delivers a 24 volts DC out. the problem that I found was a lot of cold soldering and I fix that and it worked, now the problem is that it works and shut down after it has been on for an hour or so. Do you have any Ideas as what could be the problem? I am attaching a picture of the board.

Best Regards,

Andre

Hi Andre,

Try check to see if there any more dry joints in the board. try also gently tap/knock on the power supply to see if it will shutdown. Make sure you test the power supply with load.  Keep me update on this.

Jestine

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

Hi Jestine, I need your help once more. I have a power supply board the has a 220 Volts AC supply and delivers a 24 volts DC out. the problem that I found was a lot of cold soldering and I fix that and it worked, now the problem is that it works and shut down after it has been on for an hour or so. Do you have any Ideas as what could be the problem? I am attaching a picture of the board.

 

Best Regards,

Andre

Hi Andre,

Try check to see if there any more dry joints in the board. try also gently tap/knock on the power supply to see if it will shutdown. Make sure you test the power supply with load.  Keep me update on this.

Jestine

Hi Jestine, thanks for your response. I double check the board under a high power Magnification lens and found that the inductor coil had a loose leg and one of the filter cap as well, I repaired and tested it for an hour and more with no problem…Thanks again for your help.

Best Regards,

Andre

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

From: Simon Dolan
Subject: SMPS REPAIR BOOK

Message Body:
Hi,
I’m an electronic technician earning money with electronics musical equipment. Today, I’ve decided to buy the book about smps because I had problem with a smps. I studied smps at repair school but there are so many things to learn that I’ve forgotten some of them. With the help of the book, I was able to repair the smps within the day.
Thanks Mr Yong
You are a light in electronics repairs!

Simon Dolan
macdolan.com

(You can use this as a testimony for your book)

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

Hello Jestin, I have a problem with my 14″ CRT Monitor TV. As soon as I turn it on it starts to produce high-pitched sound and when I open and watch the back side of the monitor I see a colored spark coming out of my monitor. My wife is so scared she doesn’t even want to turn on the TV. Can you help me solve it?

Hi Tagel,

If the color spark out from the flyback then the flyback have tiny break and need to be replaced. If the spark out from the crt then it could be the crt tube have problem of the flyback produce a higher voltage than normal. In this case you need to check if the B+ supply voltage to flyback ir good or not.

Jestine
http://www.JestineYong.com

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Hi mr yong i have a 21″ and 29″crt tv which shows redish and greenish help.

Hi,

If you can demagnetize it using a degausser then the tube have problem. If you can demagnetize it then check for bad posistor or dry joints.

Jestine

 

 

About

Jestine Yong works as an Electronics Repair Lecturer in Kuala Lumpur Malaysia and his training website is http://www.NoahtechElectronicsTraining.com. You can check out his repair blog at http://www.JestineYong.com