long time and happy new year, we are doing well in KENYA. i need help on this LCD monitor and i have seen this problem on Lcd Tv  eg  if I type the letter A on MS Word, there will be a shawdow A next to it.

HI Ibu,

Thanks and happy new year to you too. In your case if all the output voltages are good and stable then the problem is in the lcd panel.  Try reflow the lcd controller/t-con board and if still the same then you may need to replace the LCD panel.



I did it Jestine!
Went last night to install and it fired up and ran.
It is a good feeling to finally fix 1 after trying to do just that for many months.

Remember when I told you that I wanted to learn about repairing automotive computers?
It was because of you that I decided to do it.

I have learned so much and a lot of that is because of you.
Told you that I appreciated you and all your efforts in helping me with my endless amount of questions. You have helped launch a new career.
Thank you my friend and teacher.



hi i got some ebooks from you and coming along fine.i am working on a sony cd player for a car and got a transistor (d2396).need to know the info on it like output volts.the only thing i know it i a positive transistor and if ican replace with identical one.thanks

HI Noah,

According to my databook the equivalent part number are: 2SD1273,2SD2092, 2SD2156 and 2SD2375.

Here is the spec:


Have a good day!


What I mean is what causes the bright dot in the center of crt tube when the display disappears?


Hi Boling

The dot can be caused by weak tube or the pc tube ground is not connected.



Hi  I have a problem on a samsung 32 inch lcd .The problem is that the picture comes up for few seconds and then disappears all the voltages on the power supply are ok ,at first we suspected the invertor boards ,replaced it but does the same as the old one ,would the screen cause this problem ,but yet when you switch on the picture and sound are perfect ,any suggestions ,also the t panel seems ok .DB DULLABH

It could be one of the backlight have problem since you already replaced the inverter board.



hi mr yong

i need  ask you about lg 26” tv lcd.  i have a tv lcd moel lg rz.26lz50 first time work good after one or 2 h i have only voice and the picture gone and the display gone white. thank you

Hi Elmekki,

It could be the fault of the lcd panel or the t-con board. make sure the supply voltage to the t-con board is good. Check to see the output voltages from the power supply are good and stable.



Dear Sir ,

I got one atx power supply send in to repair with the complaint of no power , as i go throught it i found it got 5vdc at the stand line can you tell me which part of it i need to check cause at the primary side i can’t located any faulty component . Just want to know can i replace the ic IFFR8M0249E with TL494 . Thanks

Hi Chong

I’m not sure about that part number but TL494 is equivalent to IR3M02.

Did you connect to the motherboard and test. Try follow the power ” on” wire and see if it is coming from a transistor. if the transistor is leaky the power supply will not be turned on.



Hi Jestine,

Happy Chinese New Year to you.

My name is Chong and would like to seek your advice.

Actually, I’m looking into a voltage regulator that able to accept DC input from 12-48Volt and output as 10-24Volt.

Which option should be better, a standalone voltage regulator or to built 1 with Zener diode, resistor and etc?

I have zero knowledge on electronic and trying to figure out.

Look forward for your advice.

Thank you.

Hi Chong,

Thanks- try modify from this circuit below:


Voltage regulator is much better and stable than  usign the zener diode circuit

The output is 1 ampere for LM317T IC



Jestine I am looking for a transistor #D2102  for a Precision television, but it is very difficult to find this transistor.
Do you know this transistor or another transistor which I can use?


Hi Tyrone,

According to my databook the equivalent part number are 2SD1585, 2SD1913 and A2SD1406.



HI George,

Selamat pagi sir Jestine,

You know the local greeting-that’s great!

sir can yoiu pls help me how to diagnose CRT Monitor  (AOC, product name: 7Vlr, Model no. 1770). The problem is Blur picture i already adjust the focus and still it is blur i can’t read the letter very well, when i opened a document word. but before that the monitor have so many unsoldered joints , i resolder it because when the costumer bring it to me it is have a problem a no oscilation and after i resolder it become alive. the problem now is the blur picture.  terima kasih tuan terlebih dahulu.


Blur picture is usually due to bad flyback or the picture tube but chances is very high on the flyback transformer.



HI Roselle,

I’m really thankful for the newsletters that you are sending me. It help me improve my skills in troubleshooting.
You are welcome!

I would just like to ask you something about the trouble of our tv. Would you know how to unlock a tv? What happened was, the tv has an option of TV LOCK and it was accidentally locked. Now, I could not even change the channel, can you help me? If you happen to have the diagram this is the model MX-TVS1414A.

Sorry i do not have a diagram and you need a combination of press buttons in the remote to unlock it. Sometimes a lack of supply voltage to the eeprom ic also could also show lock display.


Hello Jestine,
I do have a question for you. I am just starting out in electronic repair
and am slowly buying a few entry level test meters.
Recently I purchase a Honeytek A6013L capacitor tester. The unit has small
instructions and I research on internet but can not find answer. Question
being- the unit has 3 sockets for the probes, looking at the meter the far
left socket say + middle socket say – and far right say +. Can you please
explain why 3 sockets and which do I use.
Thank you and Bless your work
Ohio USA

HI Bart,

I have seen the photo and I’m also wondering why they need to put an extra socket on there. Make it easy-place the balck probe to – and the ed probe to either one of the +. Then test a good cap and read the value. After that do the same thing on another + socket. If the result are the same then you can use either one of the socket for measurement.


Sir, Good day… the color of the power LED is Red. But am glad to inform you that i got the trouble. It’s the “Flyback Transformer”. This is what happened; I keep on checking the voltage at the collector of the horizontal output transistor (it’s almost 100V) and then i try to press the channel Up button, i had noticed that the voltage shoot-up a little bit and then back to 100V again. And so, i did think to check if there is an AC signal at the collector of the horizontal output and press the channel up button again, and there was but it goes back again to zero. And i had noticed also that every time i press the channel up button, the power LED indicator dimmed a little bit for around 2 to 3 seconds. And because of these I suspected the flyback, and without hesitation i did replaced it with a new one and then try to power on. I was happy when it start up…

Sir, i really appreciated so much your reply. I feel great that you respond to my email for help. And i share this little experience of mine for the hope that these may help…

Thank you so much Sir, God Bless and more power to you…

truly yours,

Hi Romeo,
Congratulation! I guess the bad flyback transformer did not feedback a signal to the CPU thus the cpu output a signal to trigger the red power led.



Hi Jestine,

I have a SANYO LCD TV where the screen goes from full blue, then full red and then green. I have checked the power supply rails and there all OK.I think the problem is on the main board. CODE: 17MB12-2. VESTEL Product.

I have saw on the internet a board with the code 17MB12-1. Do you know the difference between them? Is there anything else I should test?

Thanks in advance,


HI Bruno,

Sorry no info about the board but usually those code are referring to version. it could be upgrade of some parts that always have problem or the firmware. In your case, you need to find a way to enter the service mode because the symptom seems to be the LCD TV is running on a self test mode. Try eserviceinfo.com forum to see if anyone know how to enter the service code for this tv.



Good day sir, i hope you are not tired with our questions we know that we have no anything to reward you with this great work that you have done to us, only god will reward you may god bless you.
Sir, i have problem with this crt tv when i power it on you hear the starting sound of the tv but no display, i make voltage test i found all the secondry voltage is good only B+ is not good instead to get 125v but i get 65v, but something that give me surprise is that when i disconnect the B+ line to the playback transformer the B+ voltage increase to it’s normal voltage i.e. 125v. So sir this means should i replace the playback transformer? Because i don’t have esr meter or playback tester to test the playback transformer. Sir i hope you shall help me to solve this problem. Thanks.

Hi Mukthar,

If there is no components shorted in the flyback area like HOT, safety cap, horizontal yoke coil, secondary output diodes at flyback output pins then chances is very high the flyback have problem.





I am learning as I go (obviously).  The DVD player is auto detect (100-230 VAC).  As I have a second identical DVD player with the same power supply, I decided to compare test measurements.  I have not used this player in years, and discovered that it also does not work (you get what you pay for — $35 US if I recall).  The voltage on the primary filter cap on this unit also is 187 VDC.  On this power supply, I do get voltage on the secondary outputs, although the voltage is incorrect.  The 12 VDC reads 20  VDC (drops to 15.3 VDC under load) and the 5 VDC reads 3.4 VDC (drops to 2.43 VDC) under load.  There are two bulging filter caps on the secondary side which both test bad on the ESR meter.  I also discovered that the voltage oscillates between -0.7 and 1.2 VDC on the primary coil on the primary side in the second unit, whereas there is almost no voltage on the original unit.  As a result, I am doubting my conclusion that the transformer is bad and leaning toward a defective switcher IC.  I have ordered up 2 Viper22A’s from DigiKey as well as some replacement caps, so we’ll see.    Some of my confusion may be due to a misunderstanding of the composition of the transformer.  I had assumed that there was one primary and one secondary winding with taps (like an AC power transformer), but it appears that there are two independent windings for the primary and two independent windings for the secondary side.  Is this correct?

In any event, I am enjoying the challenge and greatly appreciate your help.  I also just discovered that you have an ebook on SMPS which I will be ordering this evening (I have learned a great deal from my previous purchase of your Testing Electronic Components ebook).  Thanks again.


Hi Ned,

Usually after checking all the components to be good, the highest suspect is either the power ic or the transformer. But generally the smps transformer is quite reliable. In smps the primary side can have 2 windings. One is primary winding and the other is a secondary winding in primary side. As for secondary winding it can have one to 5 or 6 windings. By the way tanks for the support on my ebooks.



Hello Jestine,

I work on more recent types of component repair and probably stuff that leads technology. I have some questions about diagnosing power issues and or components in general, for what I do. The boards are work on are small PCB’s from laptops with very small resistors, coils, caps, etc… I need to know how to do fault finding on these and do it quickly and be able to train new employes to expand. Please give some ideas or help with this, we have been in business for over 8 years in the is one store and 18 years in our other store, and unfortunately technology changes most of the stuff in your guide doesn’t apply because this stuff is newer.

thanks best regards,


Hi Don.

Troubleshooting smd boards need different type of tools and test equipment. You need

smart tweezer to check on smd components

huntron tracker to compare between two identical boards

you need rework station too.

Lastly is your skill-the more you practice the better you are.




IN reading your book.  I was trying to apply your technics to a repair that I am doing.  The one where you use a 100 watt light bulb in series with the fuse.  THe tv is a LG model# 47LG50-UA no power with a slow flashing red LED.  When I connect the light bulb across the main fuse.  I did remove the fuse and connect the light bulb.  The light would come on dim for a few seconds and then go off, and not come back on.  I have checked every component in the primary, and secondary section, and then replaced the power supply.  THe new supply did the same thing.  I also replaced the backlight invertor boards and still the same thing.  I checked the 3.3 volts at the power button, and it was good  One the power supply I have all the voltages that are suppose to be present.  Since I installed a new power supply, I don’t think it is the power supply.  I followed the power button assembly to the main board, and found some missing voltages.  I think the problem is on the main board, but my question is why is the light bulb not staying on?  Your book doesn’t cover Dim like and then it goes out.  Any ideas?

Thank you

HI Dave,

A good power board the light should come on (sometimes dim and sometimes bright) and then will settle down  to off. If the light bulb staying on then the power supply have shorted components. But then again it depends on the design.  In your case when the power led is blinking one should check on the output voltages of the power supply. If it has good output voltage then the power supply is good and suspect a bad MCU in the mainboard. Power LED signal is coming from the MCU and if the MCU have problem the power LED will blinks.



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