RCA L42FHD37YX8 Will not power on

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

The backlight doesn't do that very often. I put the meter on a lower setting... ther is about .02 to .04 vols on those pins.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

ok I managed to get a test done with backlight flashing. it jumps to about .35 volt for a split second. It's pretty quick, so I am not sure the meter is getting a full reading, but there is a definite jump when I plug in the tv. Thanks for the help so far.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Ah, there is one thing you can try. You will need a 100 to 470 ohm resistor, do you have one?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Yes I have a 100 Ohm

[tom66]

Re: RCA L42FHD37YX8 Will not power on

OK, disconnect the connector running between the power board (edit: and main board), leave it connected to power board end.
Run the resistor between BL_ON and 5V.
Plug TV in, backlight should be on and stay on.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

So disconnect the cable running from the power supply and the inverter? The one with the 5 reds and 5 blacks? If I do that the inverter would get no power?

[tom66]

Re: RCA L42FHD37YX8 Will not power on

No, leave that one connected -- disconnect the other.
Edit: should be between power & main that is disconnected.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Well if I did it right...no backlight...no blue led either

[tom66]

Re: RCA L42FHD37YX8 Will not power on

No blue LED is expected. Can you take a photo of what you did so I can make sure it is correct?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

here you go

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Sorry, a misunderstanding: the jumper should be on the same connector only. You can stick the resistor leads in the holes of the exposed connector (disconnected from the main board end.)

For clarification: power board is in that photo, main board has the video inputs on it.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

I still seem to be having some confusion... I attached a pic... the connector that has bl_on is different from the one that has the 5v. What am I missing?

Thanks!

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Huh, that's weird. The BL ON and DIM pins should feed through straight to the inverter connector. Can you use the continuity mode on your meter to tell which connects to where?

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

BL_ON and DIM go to the inverter. It also kinda looks like there is a BL_on in the cable going to the main board as well. the connector has two rows of pins, one above the other and the label says dim bl_on so I am wondering if dim is the top one and bl_on is the bottom. Tried the tests and still nothing.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Oh I was getting confused by how there are like 12 labels and only 8 pins. That explains a lot! In cases like that, it's a matter of placing a piece of wire in the appropriate hole to get a good probing position or place for the resistor.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

Ya I tried...no backlight tho. So are we thinking at this point that the power supply is good because it shows 24v properly?

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Yeah but it seems like you may have a bad backlight inverter or main board.

When you place that 100 ohm jumper, please check what voltage you get on the BL ON pin by measuring directly at the inverter pin connection (on the power board.)

Also, see if you can plug in a working video source that produces audio, and see if you get sound, you may have to blindly select the source.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

So I found out that depending where I put the resistor, I can get 5v on either dim or BL_ON on the cable going to the inverter. However I no longer have the 24v on the 5 reds so there must be something else that turns that on. There was a pin labeled pw...would it need the 5 volts as well? Thanks for your patience in this.

[tom66]

Re: RCA L42FHD37YX8 Will not power on

Yes, it would be PW likely, which gives you 12V and 24V, then BL ON which turns on the inverter. DIM controls brightness, can be left alone for now.

[Snype32]

Re: RCA L42FHD37YX8 Will not power on

OK so I did a little experimenting... When I plugged everything back in as it's supposed to be, the 24 volts was back as was the 12v. BL_ON was not getting 5v, so I jumpered from the 5v source to the BL_on and sure enough, on it came. No menu or anything, just the backlight. So are we now looking at the main board?