Problems with diagnosting problem with tv power supply board/backlight board

Hi Tong,
Any basis or reason to replace the two boards you replaced? Any voltage measurement? Further you have not mentioned the make and the model number.
Generally it is the inverter board that is found defective in 'no backlight' problems. If the power supply is producing necessary voltage and the main board is sending necessary command ie 'inverter on' and 'brightness control' to the inverter board and still it not producing the voltage required to drive the backlight, the inverter board is defective.
Good luck.

Check for any loose soder points or loose connections with wiring sockets to backlight inverter board.

Good day!!!!

If your TV turn ON/OFF itself without sounds..The possible problems are voltage drop on power supply,overheat/overload,loose/cold solder of power supply or bad T-con board..

If you already inspected all capacitors on the power supply and all looks fine but it doesn't mean that your power supply board works fine because sometimes bad capacitors not look like bulged or looks fine visually but the value change its either lower/higher capacitance value.In that case you need to use capacitance meter to find bad caps..But before we do that,I have a procedure to minimize/eliminate troubleshooting.In this procedure you need a multimeter tester to perform voltage data check..

In this procedure we can determine where the fault came from..

This are the steps:

1. Open the back cover.
2. Look at the power supply board (it is usually connected directly to power cord).

3. Find the 3 long connectors near the aluminum heat sink.Those connectors having voltage marks on each pins so you can easily determine where did you get the voltage..

4. Point the black test probe to GND (ground) and the other probe (red) to 5vdc,12vdc/15vdc,24vdc..Let me know if you find any voltage drop or voltage lost..

5. If all voltages are works fine..The possible problem is on T-con/logic board or main board..But in that case the common problems is on T-con board I found it online $34..

Hope it helps..Just keep on touch to fix your TV and works fine again..

Regards,
Chester Pendilton.

Hi Alfred Grace,

First of all, thank you for posting your question here at Fixya.

Based on the symptoms you've described, I don't believe that the backlights are already faulty. If backlights gone to malfunction, that are permanent, but in your case you've said that the TV power up fine for half an hour, this is an indication that the fault not came from the backlights but from the inverter boards. Inverter boards are the one giving high voltage to the backlight to light up, it has a built in protection circuit that will activate once there's a malfunction on the board to avoid further damaged because of high voltage output.
If you would like to fix it yourself, I would advice you to replace both the slave and master inverter board. I saw your board at shopjimmy.com. Click it HERE for the replacement. Replacing these boards are not technical, all you have to do is to unplug the unit overnight to drain any voltages from the power supply board, disconnect all connectors and then put-in the new boards. No soldering required. If just in case that the inverter boards are not the issue (I'm pretty confident that the power supply board is working fine), don't worry, the link I've provided accepted return, the fault is on the power supply board.

Hope I helped you.
Have a nice day!
Good luck and take care!

Jdvillanueva

Hi ,
Power on the unit in the dark room then aim a bright flashlight directly to the screen, you will barely see the images. This is because your backlight is not functioning. The following reason is the caused.
1. Power supply - missing B+(supply voltage) coming from this board feeding the inverter board. This is caused by faulty transistor, dried/leaky electrolytic capacitor, open fusible resistor.
2. Inverter board - even the B+ is good from the power supply, if the fuse, driver transistor, driver transformer is faulty no output to the backlight resulting to black picture.
3. Busted backlight - even inverter board is good but if this is busted resulting to black picture also.
Diagnosing the fault is technical and if you don't have necessary tools and test instrument and can't fix it yourself, I would advice you to look for an experienced technician to isolate the problem.
Hope I helped you.
Have a nice day!
Thanks for using Fixya.

Hi elav2,
Power on the unit in the dark room then shine with the flashlight directly inthe screen, you will barely see the images. This is because your backlight isnot functioning. The following reason is the caused.
1. Power supply - missingB+(supply voltage) coming from this board feeding the inverter board. This iscaused by faulty transistor, dried/leaky electrolytic capacitor, open fusibleresistor.
2. Inverter board - eventhe B+ is good from the power supply, if the fuse, driver transistors/IC's, high voltage transformer is faulty no output to the backlight resulting to black picture.
3. Busted backlight - eveninverter board is good but if this is busted resulting to black picture also.
Diagnosing the fault is technical and if you don't have necessary tools and test instrument and can't fix it yourself, I wouldadvice you to look for an experiencedtechnician to isolate theproblem.
Hope I helped you.
Have a nice day!
Thanks for using Fixya.

Good day!

Please before we go to the further troubleshooting please to play a DVD or recorded shows to determine if the problem is in your TV or cable connections.

If the problem persist please try to replaced this simple procedure on how to fix that problem.

1. Remove the back cover of your TV.
2. Check the 24vdc from the power supply going to inverter board using multimeter tester (range on DC)
3. If you have 24vdc on the input voltage of inverter board,try to check the output voltage of that board,it should have 500vdc going to the cathode light inside of TV (back light)
4. If you don't have the 24vdc on the inverter it means your power supply got trouble.
5. You have better chances if you have failing capacitors on the power supply.Just look the image of capacitor if it is leak/bulged on the top.

If the problem is still there and you have other question just add a comment

I hope this solution will be helpful.Thank you for using FixYa.

Hi memom440,
Power on the unit in the dark room then shine with the flashlight directly in the screen, you will barely see the images. This is because your backlight is not functioning. The following reason is the caused.
1. Power supply - missing B+(supply voltage) coming from this board feeding the inverter board. This is caused by faulty transistor, dried/leaky electrolytic capacitor, open fusible resistor.
2. Inverter board - even the B+ is good from the power supply, if the fuse, driver transistor, driver transformer is faulty no output to the backlight resulting to black picture.
3. Busted backlight - even inverter board is good but if this is busted resulting to black picture also.
Diagnosing the fault is technical and if you don't have necessary tools and test instrument and can't fix it yourself, I would advice you to look for an experienced technician to isolate the problem.
Hope I helped you.
Have a nice day!
Thanks for using Fixya.

There are two places to look for the problems, the backlight inverter board and the power supply. Look at the power supply first since it is easier to get to, look for burnt parts, bad capacitors, etc.
http://en.wikipedia.org/wiki/Capacitor_plague
Parts: http://www.shopjimmy.com/catalogsearch/result/?q=Vizio+VX32L+
Please post back what you find.

There are two places to look for the problems, the backlight inverter board and the power supply. Look at the power supply first since it is easier to get to, look for burnt parts, bad capacitors, etc.
http://en.wikipedia.org/wiki/Capacitor_plague
Please post back what you find.