Proscan PLDED3996A Won't Start... Some done, what next?

[Overlord500]

Hi folks,
I'm hoping you can help with this TV. It was given to me, broken. When plugged in, it gives a red light in the corner. When the power button is pushed, the light turns blue, but nothing else happens. No sound, no dull image, nothing. The screen has no damage, as far as I can tell. Of note, I've never tried to hook up a device to the TV... seems unnecessary, but perhaps it needs a signal coming in to power up?
Anyway...

I've already replaced most of the capacitors on the power board, with the exception of 4 (the "big one", and 2x 470mf 16v, 1x 220mf, 50v). No change. None looked bad, but I figured I'd replace them anyway. Do you think these last 3 could be a problem? I did "test in place" the caps, too, and none behaved as fully "open" or "closed".

Also, I've tested some voltages and seem to be getting the wrong voltage on two wires. They are labelled 24V, but I'm reading only 12V. These connections are on the Mainboard where it is labelled "AMP POWER" and are adjacent to the speaker outputs. I have attached pictures of this board and where I'm getting these bad readings.

The power board is attached, too, with labels. I also identified the 3 transformers.

Where should I go next on this TV? I'm thinking of replacing the 3 remaining caps, to make sure, but I'm thinking it might be a transformer?

The Power board is a (on the sticker): LK-PL390101B and (on the board itself):LEKE LKP-PL065 REV:0.6RoHS 2012/03/21 (new, huh?)

The Mainboard/video board is a: T. MS3391.71

[newtothis]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Connector from PSU to Main.. What voltages do you read?

[splitcrete]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

What is up with marked diodes? Did you test them?

[newtothis]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

What is up with marked diodes? Did you test them?

Diodes?

They aren't marked on his pic, What makes you ask about these?

[mmartell]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

He marked them on the photo he put up.

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Hi,
I did label 3 components on the board, other than the caps I didn't replace. Perhaps I'm mistaken, but they are transformers not diodes. (?) I labelled them in case others had found them to be problematic on other sets.

In regards to the voltage question - there are many leads running to the mainboard with many voltages. The only ones that were labelled that had a significant discrepency are the two that should be 24 (as marked on the board) but are reading 12. Some of the voltages should be 6 and seem to be reading slightly low (around 5) on an analog meter. I will retest them after dinner with details.

Thanks, already, for the interest and responses.

David

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

I didn't circle and mark these diodes... ?

David

[mmartell]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Guys, splitcrete posted a response with a modified photo in which he asked that those diodes be looked at.

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Ahhh... I understand. I'll let you know in a moment. For a bit there, I was pretty confused

David

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Hi folks, I tested the diodes that splitcrete asked about. As far as I can tell, they're fine. Using an analog meter, they have infinite resistance one way, and consistent resistance the other way - between 10 and 30 ohms.

I did order the 3 capacitors I didn't replace yet. I will keep you all posted.

Any thoughts on how to test the transformers or what I think is the relay (directly above the power supply connector on the power board)?

Thanks again.

David

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Connector from PSU to Main.. What voltages do you read?

Looks like the output voltages are correct based on the PS board - 12volt (as labelled) and 5 volt (as labelled). I tested all grounds, too. The wires that run to the video board where that board says 24volt are labelled 12 on the output side, so perhaps this is a mislabel on the video board?

The one thing I'm not sure I understand is the red and black two wire output (at connector CN2) - which is 55volts. The way the picture of the PS board is, this connector would be on the top left. It runs into the back of the TV under the plastic casing... not sure where after that.

Also, I did test the voltage of the video output that runs to the connectors that control the LCD panel. Looks like this voltage is about 12.5volts.

Honestly, it seems like everything I can see is working correctly. Do you suggest taking the screen apart more so I can check out the LED array itself? Perhaps this is the failure point?

Thanks.

David

[newtothis]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Ok lets start from scratch.

DMM set to highest DC range ... Primary filter cap (the big one)... probe to each pin... what is the reading?

[mmartell]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

That's strange that the silkscreened voltages do not match. Are you even sure these boards are originals ?

[newtothis]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

I had the same in a set last week, set had never been opened before though

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Ok lets start from scratch.

DMM set to highest DC range ... Primary filter cap (the big one)... probe to each pin... what is the reading?

Well, I have an analog meter. Set it to the highest DC voltage supported - 300V. Pins the needle past 300 Volts. What should the voltage be here?

Thanks for your continuing help and support.

David

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

That's strange that the silkscreened voltages do not match. Are you even sure these boards are originals ?

Yeah, it's really odd, I agree. Yep, these are original boards as I broke the "seal" when I cracked the case for the first time - killing the warranty, which was past anyway.

Looks like the power board and the main board are designed to also support a version of the set with a built in DVD player, but this board/set doesn't have this feature. Perhaps this might explain the discrepancy in the labels.

Thanks.

David

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Well, I have an analog meter. Set it to the highest DC voltage supported - 300V. Pins the needle past 300 Volts. What should the voltage be here?

Thanks for your continuing help and support.

David

In thinking about this, is it safe to assume that the voltage listed on the capacitor should be the voltage running across the capacitor? If so, I could check all of them with the TV turned on and see what I get at each capacitor.

Also, would it be useful to try hooking up a VCR or another video source to the TV to see if I have sound? Just an idea.

I hope everyone had a great Thanksgiving!

Thanks.
David

[selldoor]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

No - the voltage stated on the cap is the maximum it is rated for. The measured voltage on it could be anything up to that. Usual low voltages are 1.8 3.3 5.0 12.0 24.0

Really you need to get a digital meter to read up to 600vDC If this is just a one off job
a $5 would do at a pinch. Depending on the set it could be around 390vdc

[Overlord500]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

Thanks for the response. My father is getting me a digital multi-meter for Christmas - he always is looking for gift ideas. I did some work on that TV - it does produce the correct image on the LCD, seen with backlighting provided by a flashlight. Just the LED's are not lighting up. I took that apart, too, and am curious how to test the "light bars" individually. Looks like they are wired in series, so if one LED has failed, the TV will not produce backlighting. The voltage going to the backlighting was 64 volts. Perhaps this is too high and burned one LED out?

If I needed to replaced a single LED (they appear to be 4 pin) where might I find one? Any thoughts?

Thanks again.
David C.

[selldoor]

Re: Proscan PLDED3996A Won't Start... Some done, what next?

I dont know anything about LED backlights (must learn I suppose) But have a look on this site http://www.lcdparts.net/ they might have some info. I would look but am just off to bed.