Polaroid TLX-04244B Image, but no backlight (No separate inverter boards)

[Oran]

Hi all, long-time lurker, first-time poster. I've been fixing TVs for a while now, but I don't have all the answers by any means. You guys have all been a big help, and I'm hoping someone may have some feedback for me on this one as I'm a bit stumped. Thanks in advance for your time!

I have a Polaroid TLX-04244B. It was having one problem, I attempted a repair and now it is having a different problem.

Initial situation (Essentially solved, apparently):

- When turned on, red standby light flashed repeatedly (no sequence)
- Had to unplug it to turn it off
- No visible bad caps on power board or main board

Did a bunch of research and found that it seemed most likely that the main board needed to be replaced. I ordered a main board from shopjimmy and replaced the unit. (Original p/n 0708090342, Replacement p/n 0708090343, both mfr p/n PV420TVM-A81H. I may have made a mistake here, as I replaced a 42 board with a 43 board...but I think they're compatible. I needed to use some "ebay bucks" so I took a gamble.)

Now the situation is different, and seems like a VERY common problem in this set.
(NOTE: I have the power board with built-in backlight inverter. No separate inverter boards.)

When turning the TV on

- Power light flashes blue 4x
- Polaroid logo flashes on screen
- Power light flashes 2x then remains solid
- Red light on power board flashes quickly, constantly. (This is troubling.)
- I CAN see the image on the screen with a flashlight!
...so it looks like the main board is working & TCON is good, but no backlight. I assume this is either due to the power/inverter board or the panel/CCFLs.

To recap briefly: There is an image, but no backlight.

On the power board CON3 I am reading proper voltages on 12v, 5v & 5vSB. I am not sure where to test 24v from.

If I disconnect the LVDS from Tcon I get the exact same behavior minus the Polaroid logo. No image...makes sense.

If I disconnect the white backlight cable (only one harness), I get the same behavior except no backlight of course and a couple subtle clicks when I suppose it is trying to kick on the BL, same blue light pattern and the red light flashing on the power board is a bit slower than before.

I suppose my questions/comments are:

- I hear no buzzing. Is it possible I have malfunctioning backlight/s? I've read some info about arcing causing the inverter/s to shut off. (I read one post in which someone stated they removed and cleaned all the backlights and it resolved their problem.)

- Is it still possible that I have a bad power/inverter board? The BL does come on briefly, but then shuts off. I'm not quite sure what to make of that. It seems to be capable of powering the BL, at least momentarily.

- I have tried a variety of settings with the dip switches on the power board (without really knowing what I'm doing), to no avail. Is there anything specific I should try with the dip switches?

- Is it safe to assume that the main board replacement itself was successful and that the part is compatible, as the initial non-functional state was resolved and I DO now have a picture?

I'm not sure where to go with this now, and shopjimmy is not operating their tech support at the moment.

Here's what I want the issue to be: Bad power board. Replacement will resolve the problem.

Here's what I think it probably is: Malfunctioning backlight/s causing inverter/s to shut off. Probably a very difficult fix.

Any help or feedback is greatly appreciated!

Thanks!
- Oran

[Oran]

Re: Polaroid TLX-04244B Image, but no backlight (No separate inverter boards)

Did I provide too much information? :/

TL;DR: Replaced bad main board. Now have image, but no backlight. Do I have a bad power/inverter board or bad backlight/s?

[selldoor]

Re: Polaroid TLX-04244B Image, but no backlight (No separate inverter boards)

Did I provide too much information? :/

Its a bit much but its probably the lack of pictures. Many of us may never have seen the boards you are talking about and even if we have can we remember what they look like. I for one am not going hunting round the internet to see one.

I am a bit surprised if as you say you are a long time lurker you have not heard pictures mentioned before - like one in 5 posts?

[Oran]

Re: Polaroid TLX-04244B Image, but no backlight (No separate inverter boards)

Thank you for the response! I know pictures are important. I'm sorry, I have a fine motor tremor (I shake somewhat badly all the time) and so my pictures all turn out nearly useless, especially when detailed things need to be identifiable. (One reason I went a bit nuts on describing things.) I was thinking that this seems to be a common problem with this set & I suppose I was hoping someone familiar with it would chime in. After looking over some of my questions, like the one about freakin' DIP switches of all things, I realize I may have made a big mistake not getting some pictures attached. I'll see if my roommate can give me a hand this evening and I'll get some good pictures attached.

In the mean time, this is the power/inverter board I have, in case it helps: http://www.shopjimmy.com/polaroid-86...upply-unit.htm