RCA L42FHD37YX8 Will not power on

[Snype32]

Hi,

I just found a RCA L42FHD37YX8 at our local dump. When it is plugged in, A blue LED comes on. Nothing happens when the power button is pressed. I opened up the back and looked at the power supply... All caps look good. Is there anything I can test for? Thanks!

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Can you get any pictures of the boards in the set?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Sure...here you go. Thanks for the quick reply. These are the two main boards. To get pics of the inverter would require some more serious surgery. I did notice one cap has what looks like a bit of a dent...but I kinda doubt it's the cause of the problem.

Thanks!

[tom66]

Re: RCA L42FHD37YX8 Will not power on

So, I see some pin markings on the connectors going to the main board, can you list them?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

OK so on the bottom connector on the pic...

5 red wires = 24v
5 black wires = Gnd
1 Green wire = bl_on
1 blue wire + Dim

Second connector

Green wire = Dim_bl_on
Blue wire = Gnd PW
Red Wire = +5vSB
Black Wire = Gnd
Red Wire= Gnd+12v
Red Wire = +12v
Black Wire =Gnd
Red Wire = +12v

Thanks for the help!

[tom66]

Re: RCA L42FHD37YX8 Will not power on

OK, check the voltage on the +5VSB.

To do this: multimeter on DC volts scale (20V if manually ranging), black probe on metal chassis (e.g. back of LCD panel module, wall mount...), red probe pressed into pin in question.

What do you read? Should be around 4.75V to 5.25V.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Looks like I'm getting 0.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

You have a power light while you are doing this? TV plugged in?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Yes TV is plugged in. Bluish light on. Sometimes when I plug it in, the front LED goes a deeper blue, Flashes green for a split second, then goes back blueish green. During the green flash, it looks like the backlight flashes as well. It does not do this every time.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Please show me what setting your multimeter is set to, also try checking a fresh 1.5V battery to check it is functioning properly.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Ah sorry...just double checked...I was on the wrong pin... now getting 4.95 or so. Sorry for the confusion.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

OK, next, check the PS_ON line both before pressing the power button and after. Check it also upon immediately inserting power cord.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Do you mean bl_on? I have no ps_on.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Uh... sorry "PW". Is that on a separate wire?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

It's one wire and as far as I can tell it says Gnd_PW. It's green. I did the tests and got no voltage on any of them.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

What do you get on the +12V and +24V?
Is there any additional board in between the AC power cord and power supply?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

I get 12v and 24v. There are no extra boards between the AC source and the main board.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

It looks like this might be an "always on" type power supply.
What do you see on the DIM and BL_ON pins, which is the one with only +24V x 5 and GND x 5 on it?
If the BL_ON is varying, the main board is stuck in a boot loop = replace main board (unless easy-to-find fix found.)
But if it is steady, then it can only be an inverter fault, which seems more likely.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

I get 0 on those pins.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Even while the backlight is flickering?