Electronic Repair Questions/Answers and Testimonials- Part 21
Here is your questions and answers:
I am very happy I bought lcd repair monitor I learned a lot
Glad that you like the book.
Just in one week-I am going to buy the plasma and the lcd repair guide.
You may visit my repair friend Mr Kent’s websites at:
Please send me other E-books that you have about electonic repair.Im a technician Im
employed .there is one question .
I have only these ebooks:
Hello Jestine Yong,
I saw the pictures of the report, opened the monitor and found the defect transistors. Three minutes later the I repaired it.
Your Zener Diode Tester is very good. It gave more insights about the zener diode. Hope you can share more of your knowledge in electronics. Though I have not finished reading the e-books that I have purchased I can see that your presentation of the topics are easy to understand. Hoping for more. Thanks.
Hello again Jestine.
I have a Sony SDM – HS74P LCD just given to me. I am suspecting the back lights are at fault because this particular lcd stays on for almost 15 minuites then nothing on screen but green power lite is still on and when you turn power off and again it comes back on for abit then out again. The back lights have only 1 wide plug on each end of inverter board.No caps blown on it.
It can be unstable voltage (you need to test the output voltages) or could be backlight have problem.
How are u? I have a SMPS bd from a DVD player that has gone bad without any 5/12 V output. I didn’t find any components with burn mark or smell bad. (Refer to the attached photo) So far i have replaced TL431 (smaller red circle) & IC 2 (bigger red circle). The IC 1 TOP224 (green circle) looks fine. Any suggestion where i can go from here? Thanks! Have a nice day.
If you have tested all of the components in the primary side and the output diodes from secondary side and still no output voltage then suspect a bad TOP224 IC or a shorted smps primary winding.
Thanks Jestine. I am enjoying testing electronic components. It is definitely worth the price. Quick question, do you have any recommendations on where I may find a portable 1:1 isolation transformer similar to the one you have pictured that you use?
Thanks for the support! About the isolation transformer, it was custom made one. Try visit this website:
As it has the variable isolated transformer which is good for electronic repair job.
Have a good day!
I also see you have a great deal of knowledge regarding Electronic Test Equipments;
If it possible could you send me a list needed by Electronics Technicians and probably some good suppliers.
Here are the list of the test equipment:
The first till fifth items you may visit http://www.tenma.com to buy it while the other two you can buy it from my website.
i fixed 3 monitors but it last for a month . 1* i have 2x HP 1503 monitor i have changed pico fuse both of them and i cant find the pico fuse so i put normal electric wire and its working for less than a month,u recomend i have to replace with pico fuse.(NOTE)
at this stage both are turn on for few second and turn off after few second.
2* i have another compaq 17 ” and i changes 3 filter capacitor and its
work for a month and now its doing same thing after few second it turn
please let me know ASAP your book is very help full for me
You have to recheck again the e-caps and any dry joints or not. If all tested okay then the problem is in the back light most likely.
Here is your questions and answers:
Thanks for the short report.
I really like having some pictures to look at. Here is my situation. I pickup two Dell 15″ LCD monitors 153FPb for free from work. They turn on for a second when you push the power button and you see the screen which has a red tint to it and then it’s back to black screen. I purchased a new Benq Power board and a new Benq Logic board for about $65.00. I installed them and the monitor still doesn’t work. Can you please advise me on what to check and do next?
This could suggest a weak backlight thus the inverter shutdown by itself. Some times a bad lcd panel may cause similar symptom too.
Do you offer any repair service and If you do what is your fee?
May i know where are you from? I only repair for local market only and the price is depends on the parts changed.
I would really like to repair them myself, if possiable. I enjoy working on electronics, but I am fairly new at it. I am starting to take the LCD panel apart further tring to get to the Cold cathoid lamps. Could that be the problem?
thanks alot Mr “Jestine Yong” you are realy a great man
and i hope that u are ok
take care and have nice day
You are welcome!
Hi Jestine Yong,
first of all i would like to thank to you for your kindness and generous.
I am currently reading your website and i really love to read, it helps me lot of information
and gaining me more knowledge on how to test an electronics parts..
its great but before i purchase your LCD book repair
i just want to colsult to you my Samsung model 740 LCD Monitor no power
when i troubleshoot i found out that the MBR10150CT are defective when
i replaced it nothings happens but it works because when i touch
the heatsink attach to it are hot. what are the other posible problem for my
Thanks for your interest in my ebook. In your case, it could have been some other short circuit further down the circuit. Did you check the output voltage? Just place your red probe to the center pin and black probe to ground.
I am doing performance tests on 4 transformers. One is a 50kVa transformer,
35Kva transformer and 2 transformers which supply power to the gerneral
purpose outlets in my galley onboard the ship.
I have to do the following tests on the transformers and don’t know how to
to do them.
a) no load lossess and no load current
b) load losses at appropriate reference temperature
c) measurement of winding resistance
d) insulation resistance
Any help on this would be greatly appreciated
I have not done this kind of test beofre thus i could not give you any expertise advice on this subject. Try key in the keyword “hi pot transformer test” and you will get some related information to your question.
I got your November news letter, it was good.
I have a problem relating fuses. I have a equipment which uses 32mA / 250V fuses, now it is blowen and do not find it in
First when the equipment came in my office, I checked it with Digital Multimeter with minimum range, it showed me “280 to 285 ohms”.
Any suggestion for this sir.
Try visit this website:
The best is to get back the same rating of fuse.
Here is your questions and answers:
Thanks for the ebook,it really helped me a lot! I hope i can repair now our monitors and motherboards.
All the best to you.
I have a question for you, is it possible to use time 100k (x100k) to test transistor, optocoupler, zener and diode since my tester has no 10k ohm selector?
No it really can’t because the x100k ohm meter does not have the 9 volt battery in it thus it can’t trigger some of the semiconductor under test like the fet. Since now sunwa analog meter is cheap i guess you should get one.
Another one, please let me know how to purchase the ECG Master Replacement Guide Book (Philips) online.
The ECG book had stopped its production and taken over by http://www.nteinc.com You may check any data from the website search result.
I will appreciate your help very much.More power to you and your staff.
You are welcome!
Good Day Sir,
Thank you for the up-date.We have been too busy last week ago,so just now I open my e-mail and see the nov. newsletter. It’s great,I found it very helpful specially to those who don’t have an oscilloscope.I highly appreciated this kind of website that help enhance the knowledge of electronic enthusiast like me.
More power and God bless.
Here is your questions and answers:
Thanks for your emails.
I put on my 21inches LG TV three days ago and it showing a blurred and dark image. The color too is not right.
Try check the CRT board area, most probably dry joints. If all the voltages at the CRT tested good then it may be a CRT picture tube fault!
And the remote could not control the TV even after I changed the remote control batteries.
It could be the remote controller itself has problem or the circuit in the tv that has turned bad. Try remove the tv cover and check the remote control circuit for any dry joints and bad components.
I got a proview 15″ monitor that has a blurry display at the side of the
screen, at the center is ok, only at the sides. what might be cause of the
If the back focus adjustment won’t help i guess is the crt tube problem!
I have a DC power supply with voltage and current settings on it. If I use it to power LCD’s I get that don’t have power supplies how should I set the current?
You don’t need to set the current in fact your dc power supply is registering the total current draw from the lcd.
Lets say the LCD requires 12 volts at 3.0 amps. Should I set the DC power supply to 12 volts and 3 amps?
You cant’ set that. It depends on the spec of your dc power supply whether it can handle more than 3 amp current draw from the lcd. That means if you have a 5 amp dc power supply then it will be good. If you have a 2 amp dc power supply then it is not suitable to use as your dc power supply would be overload.
Im not sure if I set it to 3 amps if it will push 3 amps into the LCD rather than just have 3 amps available if the LCD pulls it?
It is current draw by the lcd
I don’t want to force 3 amps into it and burn it up. Please advise. And thanks again for the help.
The thing that force and burnt up the components is the voltage. If you use a higher voltage then surely it will burnt up the components.
Hope this helps!
greetings my friend, hope this message finds you well.
I’m fine thank you.
i have a question for you. I am dealing with a lot of smd and I need to buy a heat soldering equipment. what is a decent brand to buy
A good brand like hakko and goot will usually very expensive. Nowadays there are lots of cheap china made brand in the market. The one that i’m using also made in
and how can I get more information on how to use this heat soldering thing. thanks
You can visit you tube and by doing your own test on used motherboard. As for me i will set the temperature to about 450 degree celcius and controls the air flow depends on type of components that you want to work on it.
Jestine, I recently purchased a oscilloscope, and i was wondering if i have the right scope.
The primary reason i won’t to use this scope for is servicing LCD, analog and flat screen TV. The specifications are… digital storage scope, color display ,150 mega Hz, 2 channels, and triggering such as TV…
You got a very good scope . I wish i have that spec you are having now! My scope is only analog and 50 Mhz.
THANKS ALOT U’VE HELPED ME MORE THAN U CAN IMAGINE THANKS ALOT WISH U ALL THE BEST AND ALL THE BEST TO YOU
It should be 4.62 amps. How do I test the amperage? Where is the best place for me to get an ESR meter?
Since you already know about the ampere of the adapter then we know that this is the maximum amp that the adapter can deliver. For your information you can’t test the ampere just by connecting your meter. You can only test how much is the ampere consumption by the load. Break the voltage line and in between the line connect the dc ammeter and make sure there is a load. Power on the load and you can see the current (amp) drawn. You may visit my website to buy the esr meter at http://www.electronicrepairguide.com/blue-esr-meter.html
Here is your questions and answers:
These days I’ve been repairing a computer smps, but still no result. The condition of the problem is no output voltage at all after shorting pin 14 PS_on to pin 15 GND, and the smps big fan is not revolving too. It’s the same whether it has load or not. I don’t see any component has burning mark on it, the fuse is still good and I’ve tested almost all the active components like Diode, D13007 PowerTR, 2N60 FET, SBL2040 Dual Schottky, Optocoupler, Shunt Regulator IC TL431, PWM IC KA7500, C945 & A733 small transistor and small ohm resistors& all electrolyte capacitor with ESR meter, they are fine. But I haven’t tested the NTC because I don’t know how to test it, and those many 1/8 W resistor. I do some voltage testing, on the big filter capacitor 330uF 200V, I got 137 Volts and at pin 12 of the KA7500 I got 1,275 Volt; by right it should have 5 Volt. Hope you could give a hint on how to repair this kind of problem. Even now it’s not worthy to repair the computer smps, but I do want to enhance my skill on repairing smps.
Computer SMPS is very sensitive as it has lots of protection circuit. Do you hear any sound from the SMPS or just a dead set? I had repair many that just by replacing the ka7500 ic solved the no power symptom.
Try remove all of the big transformer and use analog meter set to x 10 k to check on all of the secondary side output diode. Sometimes a shorted small silicon diode could cause no power too. The NTC can be tested with analog meter and should show low ohm.
Hope to see your 4th book to be released soon the help me acquire this skill. Thanks.
I have decided that my fourth book would be a physical book and it will be in color picture but it may take a longer time to publish out.
Here is your questions and answers:
I want to thank you wery much for the course testing electronic components. It has increased my knowledge very much. Thank you. I live in an area that was recently sffected by a flood and a lot of people lost all their electronic components. Because of your course I now find myself changing a lot of components and I actually know and am still am learning from your course. Thanks also for the Bonus Reports.
You are welcome!
I also want to ask, if you have a practical course or something like that for TV repair. I am a novice but I really want to learn how to repair TV. I bought a course from Monitor -Repair .com and it is inadequate. Do you have any recommendations. I am currently completing the 2 final modules in Basic Electronics from Penn Foster, but they no longer offer TV repair course.
The best book for tv repair is the “Troubleshooting and repairing solid state TVs by homer L Davidson” you can get it from amazon.com or any bookstore that sell used books. Try www.abebooks.com
Hope this helps!
What would be the cause for a LCD monitor to shut down 2 seconds after power on? Inverter? It’s a samsung 940N. I think I’ve read on your website that, with some monitors, they will shut down if a single back light fails. Is this true?
Yes it is true when one of the backlight fail could cause the inverter to shutdown. A bad mainboard also could cause the display to shutdown too.
Do you do eprom programming service, we dont have programmer for a few type of eprom.
please call me.
Yes only the 24cxx and 93c xx serial eeprom.
thanks every ony am very greatfull for your help for many concern pls i need your help on teaching me how to repair telivisinn and i use to go to the cafe to brose send me any infomation in pictures thanks and GOD bless you.
Try Visit this link :
Hello Mr JESTINE
Would you please tell me how can we test laser diodes.I have a CANON LBP2900 laser printer, and it won’t recognise the toner. This is the message:”insert a toner”, and it stops, even the toner is inserted and new. THANK YOU VERY MUCH FOR ALWAYS GUIDING ME IN MY REPAIR TROUBLESHOOTING.
Try check out from this link:
hi jestine how are you ..i have a power pack for printer which was defective after opening it i found it was a fuse and main capacitor that were bad after replacing the power work ..but …look the power output is 24v at 0.8 amper when i load it with 24 volt 21 watt lamp it do not work immediately it fist makes the lamp dim but when you rapidly disconnect the lamp and connect it ..it then work and the lamp become bright ..i changed the load to a fan and then the power pack work fine immediately with out having but with the lamp it is dim until i rapidly remove and put the positive wire that goes from lamp to the power pack …thanks
In that case you need to directly replace the output capacitors even though it was tested good.
What is the difference between lcd monitor repairs and lcd tv repairs.Also how do one get parts for so many model of lcd monitors.
LCD TV generally is bigger in size in term of the power board, lcd panel, mainboard, backlight and etc. LCD TV has tuner circuit while lcd monitor does not have. It is easier to work on lcd monitor than tv due to the size. Some lcd monitors has common components which is easy to get from local market while to some design it would be difficult.
What is the difference between plasma tv and lcd tv and monitors.
Here is a good website that provides the answer:
I have a DC power supply and want to use it to power laptops or LCD displays I don’t have power adapters for that im working on. How should I set the volts and amps? Lets say I have a laptop or LCD display that needs 19.5 volts and 4.5 amps. Should I set the DC power supply to 19.5 volts and 4.5 amps or set it to just 19.5 amps and leave the amps at Zero? Instructions don’t say much. I don’t want to force 4.5 amps into the LCD / Laptop, it should just be made available if the device needs it I would think. Don’t want to burn up anything.
Just set the dc power supply to 19.5 volt and it will automatically draw 4.5 amp. But make sure your dc power supply could withstand higher than 4.5 amp. For your information a normal laptops should draw very less amp.
Also I read your Ebook on finding shorts. Should I keep the amps at zero and just turn up voltage to heat up a shorted component? Im confused on how to use the amperage on the DC power supply to not burn up my equipment.
Yes, just slowly turn up the voltage and if there is a short circuit the amp reading will shoot up quite fast!
I am pretty interested in your book,but i am not sure about the suitability of your book to my job. I work as a test engineer in an industrial ups company, which i think the work is categorize as power electronics. We deal with ups in the range of 10kva to 220kva UPS. It would be good if you can advise me as we do uses high powered thyristor, transformer, inverters, blocking diodes and smaller electronic components in our control pcb board. Is there any difference in testing a power electronics components with a DMM?
Thanks for your interest and glad to know you are from
Have a good day!
Thank you so much for the newsletter for the month of Nov.
I hope you won’t mind my asking; right now I’m working on one SMPS
Moscot brand with an output of 12V. 3.33A used for an SGI Flat panel
monitor. Most of the parts I checked were ok starting from the fuse,
bridge rect, resistors, regulator, FET and everything looks good, I
don’t know about the transformer since I don’t have a transformer
The regulator is S4025L, Double diode F10P10Q and FET K2628, but the IC
you mentioned UC3842 was not in the circuit but there three small IC’s
there, namely, KA431(shaped like a small transistor) and two 4 pins IC
L0024 and L0040. Please help me.
Thank you so much.
Make sure there is supply voltage going into the power ic. So which one is power IC? Simple, trace from the gate pin of the power FET and you would find the power IC. Check the data sheet and locate the supply pin. If there is no supply voltage then it could be the power ic itself has shorted or corresponding components has problem. If there is voltage in then i guess you need to check the output waveform of the power ic with a scope. Please update me of your finding-thanks!
This morning when I switch on my Acer LCD monitor Model AL1521. There is no display even though it got power. Attached herewith 4 photos of the PCB board. I have just finish reading your ebook on ‘LCD Monitor Repair’, but I still need to review few times in order to familiarize with it. So Jestine, could you briefly tell me which section do you think should I start to check for the fault.
What is the color of the power led when there is no display? If it is red then most probably the mainboard have problem. If it is green then check all the e-caps at the inverter board. Check also the c5706 transistor (if i’m not wrong). Check also for dry joints at the round inductor. Hope this helps!
Please give me suggession regarding MOSFET.We are servicing 5V and 12V SMPS.
Please find attachment for data sheets and give me suggession.
Although the replacement number ampere is a bit lower, you may still can try it out. If possible get a higher than the 6.6 amp fet.
Here is your questions and answers:
Good day my friend,
I have read a lot of your news letters and I always visit your websites. Though this is the first time I am writing to you. I got in contact with your site when I was looking for repair tips in electronics and since then I had fall in love with you sir.
Glad that you love my website!
I bought your book on testing electronic components some months ago. I could not pay for it online from my home country
Thanks for the support on my ebook.
My story is similar to your, in fact almost the same as I read through one of the reports you sent to me sometimes. The difference is that I got a wrong carrier counsel to study Agriculture in the University instead of engineering. Now I have first and second Degree in Agric. Biochemistry and Nutrition, but the passion for electronics still remains. I have just completed another master degree in Information science and Technology in my bid to link my carrier to IT, where I felt I will have fulfillment. I have read a lot of electronic books and I have developed myself so much that I started repairing household electronics since my elementary school days till now. I do a lot of my repairs from home. I am a little bit afraid of opening a repair shop, I enjoyed working at home.I think I need more confidence and equipment to do that.
Nice to know about your background and your future plans. It seems that the electronic repair virus still remain in you although you already got the master degree!
I spent a lot of money on tools and test equipment though I have just few, which my money could buy. I have some TV’s, DVD’s, Computer monitors to repair on daily bases. though I get stocked with some of them, not knowing the way out, or not having the right kind of test equipment, and sometimes not having the replacement component for the bad components in the market here.
Its good to invest in such a good tools like the test meter and etc. Without the good meters we will having problems in finding out the faults.
I have bought all the materials for the last month newsletter project but I could not get The 30VDC meter, all I got is the AC meters of about 100V, so I could not continue till now. so many hinderances and discouragements.
You can use a cheap china made analog meter instead. Just set to 50 vdc and you are ON.
I will stop here till I hear from you. But before I finally stop, I have one fisher DVD player with power problem It came with 110v but was mistakenly pluged to 230 and it blew up. The PWM IC broke and the value written on it cannot be found. I have tried fixing it using similar IC’s but it kept blowing up violently, what do I do. I would have use another power unit but it has integrated into it the control bottons for full operation on thesame power board, is there any hope for it. It belong to my Dad.
It has to be the same part number otherwise it would not work. Have you search for the schematic from http://www.eserviceinfo.com ?
Hope to hear from you soon. Thank you for taken the pain to read my long episode, am sorry for taken much of your time.
No problem and take care!
Hello Mr Yong. I am a Dj & have too many electronic.
Nice to know you.
One is a laser system. With a problem it’s got 4 laser’s & 2 fans. Now only 1 fan & 1 laser comes on. I took it apart a the both fans came on as well as the lasers. However once it put it back together once again only 1 fan & 1 laser came on. I took it back apart but could get it back on. It’s a simple set up just power supply, dmx interface & diodes. My question is this I see you have a few book for lcds, tvs, moniters I do have a little back ground in electronics. But I’m not sure what book I can get for my set up and problem can you please gudie me on what book of your could cover these kinds of things. Thank you for your time.
Since you are dealing with the laser system i suggest that you visit this website
My ebooks only on testing electronic components and repairing lcd monitor thus it may not suitable for your work in dealing with the laser system. If you have other questions please do email me again. Have a good day!
Thank You Master Yong
You are not just an electronics engineer and teacher but a soul who
has incarnated to contribute to the advancement of technology and knowledge
on the physical plane.
It is an honor to meet you.
I am trying to repair an ATX SMPS. I checked all its primary & secondry diode & I could find two fulty zener diode PH 41/48 with countinuty test. I repalaced them but its no use, So now I need your help to solve this problem. I forgot to tell you somethign about problem. Problem is that when SMPS is conected with motherboard & I turn on the power switch of electric board, led gets on of the motherboard but when I try to turn on the power supply by power switch of cabinet SMPS dosen’t turn on.
If you found the two signal diodes 1n4148 shorted this suggest that there might be more components in the board. I guess you have to check the surrounding components of the shorted diodes.
This is A. First of all I would like to thank you very much for your interesting e-book I have gone through it, and have found it very helpful. Eventhough I have been working in electronics repairing for about three years (as a spare time buisness) now I realized that I have missed many things which I hope I am about to correct from now on .
Glad that my ebook has helped you in some way!
My first questions is about my Sunwa YX-360 TRD analogue multimeter, the ohmeter (Ohm range x1) is not measuring properly, it reads 0 ohm for any measurment (for instance when measuring the primary of 9V output transformers, which should have read high resistance, or the pointer should deflect only a little bit).
Check the X1 Ohm scale resistor inside the meter. I think it is a 18 ohm resistor may have open circuit.
Besides the adjuster of the pointer towards the infinity side (not the caliberator), I think a variable resistor, is also not adjusting.
If it can’t go to zero ohm, this mean the batteries already weak and you need to replace it.
I have another digital multimeter. I don’t have the schematics of the analogue meter. If youy have any idea, how to solve this problem.
I had igonered this analogue multimeter before getting your book, now that I know it is very important I should start using.
Analogue is one of my best tool to locate bad components. Set your meter to x 1 ohm and then open the cover and see at where the selector is pointing to. That point is the 18 ohm resistor. (it may be some other value-just resolder and test it out)
I bought the hot air station. thanks for the advice.
any way, I have a computer power supply. it is brand new. the moment I put it in the power outlet, one of the main capacitors blew. it is 200 volts, 330uf. it is kind of strange to me to see only 200 volts and the main power supply is 220 volts. is that normal?
Some smps design is different from monitor smps. It requires two similar capacitors value in this voltage doubler circuit. So it is normal.
so I replaced the below up capacitor with a new one and still it blew? any ideas? the capacitor temp. is 105c and I replaced it with the same temp..please help
Try replace the two e-cap together and make sure the thermister (if have) is in good condition. It protects the inrush current to the smps circuit. The best is still check all the components in the primary circuit. Hope this helps!
I haven’t downloaded it yet but I wish to ask if the repairs covers all LCD’s apart from Acer and Benq because mine it a Jetway Model.
First i would like to say “thanks” for visiting my website. The reason i did not mention the specific brand was because i want all my readers to grasp hold of how i solve the problem so that he or she can apply the method to solve any other brand of LCD Monitor. There is a saying “If i give a fish to you, you eat for a day. If i teach you how to fish you will eat for life!” This is the same concept apply to LCD Monitor repair. I can’t write a book of power problem for brand “A”, brand “B”, brand “C” and etc because in the market there are few thousands of brands of LCD Monitors. Then another subject of display shutdown for brand “A”, brand “B”, brand “C” and etc. I always believe this word “Once you know the principles you will know the rest”.
By the way I do provide email support to all of my buyers to help them step by step to solve their LCD Monitor problem too.
May i know what is the problem with the Jetway LCD?
Thank you for your quick reply & insight the laser system is a simple power short. I think your book may have the info I need. I did test the second fan as well as the other lasers & they work just not getting power some where in the circuitboard. I must also say for a laser system it is real simple & straight forward. Just power supply, dmx & diodes & fans all of which work with power just that the power is not going to one side of the board. But for laser it really is a simple setup. Capacitors, resistors & such I think your bokk may have the info I need to find where the power short is. But thank you for your info very much. I still think I would like to give your books a try. I also saw that you give away more than one book with your your purchase even if it help a bit or better fixes it I’m happy. But again even with the fact is’t a laser it a very simple laser.
Well, if you want to give my ebook a try then thanks in advance first for supporting my book and yes my ebook comes with other bonuses report as well. If you have any other electronic repair questions please do email me again. Have a good day!
thanks for replying me!! now i’m going to construct the “Zener Diode Tester” that you have sent as a newsletter. please tell me is it possible to use a 24V transformer instead of 12v-0-12v one? can this tester be used to check Diac also? How?
Yes you may use 24v ac transformer. Since my technical center do not have any diac thus i did not use it to test diac. If you have the diac, once you have completed the project you may test the diac out. Compare the reading with a bad diac and see the different.