RCA L42WD22YX6 - no backlight

[kevinsmith123]

I've got a 42" RCA LCD that a friend gave to me. The sound works just fine, and when I use a flashlight and look from an angle, I can see that the picture is indeed there, just with no backlight.

I've done a lot of reading around here, and disassembled the whole thing to check for any bad capacitors, but I don't find any. I will say that I'm normally a computer tech kind of guy, so I don't exactly have a trained eye for bad capacitors - I normally just pull the bad board and drop a new one in there. (I'm sure you've got a nickname for people like me around here.)

I took pictures of every board and capacitor, and have attached them to the post. If someone could check them out and let me know if I'm missing something, that would be great. I'm assuming that if there aren't any problems with the boards or capacitors, then the backlight is actually out, and would need replacing, which is probably more than I'm willing to do on this TV.

I have to admit that I don't know the names of some of the boards, so excuse my photo labelling. I also wasn't able to see any easy way to get one of the heatsinks off of the "main board", so I did my best to shoot the capacitors underneath it.

[kevinm34232]

Re: RCA L42WD22YX6 - no backlight

It looks like Pins 7 and 8 on CON4 on power supply board is your 24v inverter feed. Check for the 24v there and at both sides of the 10A/125V white fuses on the 2 inverter boards labeled SF1 and SF2.

[kevinsmith123]

Re: RCA L42WD22YX6 - no backlight

It looks like Pins 7 and 8 on CON4 on power supply board is your 24v inverter feed. Check for the 24v there and at both sides of the 10A/125V white fuses on the 2 inverter boards labeled SF1 and SF2.

Thanks. I assume the power supply board is the one I mistakenly labelled "main board"? And I just use a multimeter set to voltage to check and make sure I've got 24V on those two pins when it's plugged in? Like I said, I'm not really a pro at this circuit-level stuff - just want to make sure I'm doing it right.

[kevinm34232]

Re: RCA L42WD22YX6 - no backlight

Yep that's the power board, put the black probe somewhere to the metal chassis and red probe carefully to the connector pin, meter to set to DC. Careful not to let probe touch anything else like I've done many times.

[drpj23]

Re: RCA L42WD22YX6 - no backlight

I wouldn't be surprised if those blue caps or/and the four FETs on each of those inverters are bad.

[budm]

Re: RCA L42WD22YX6 - no backlight

Check and see if you have 24v power switch is activated, then also check the ON/OFF pin (backlights ON/OFF command) on either pin 13 or 14 of the connector attached to the Master Inverter board.

[Beatleca]

Re: RCA L42WD22YX6 - no backlight

what are the FETS?