Sanyo DP50747 50" / LG PDP50x4 T000 Panel Tv won't show video

[Webwaster]

This is my first post and I'm not a tv repair professional so please go easy on me if I've done soemthing obviously wrong and this is an easy fix but I have searched through the posts pretty hard and did not find my exact problem.

What I have is a 50" Plasma by Sanyo/ Lg parts. Lg Panel is PDP50x4T000 Sanyo Model is DP50747.

It is powering on and the screen is lighting to a glow but no picture and no menus. There are also a very few pixels that sparkle every few seconds or so. I took this tv to a local shop and they may not know what they are doing but here's what it was doing. They tested the power supply and said it was fine and checked out good. We didn't realize it was lighting because they were working on it outside because they have so many sets in their shop right now. I noticed upon inspection the Ysus board was singing. Also on the board with a chip marked LGCMx05W there are status leds integrated. Led's were as follows D2 - off D3 - on D4 - off D5 - on. Tv shop said I needed a new ysus board so I ordered one out of California. Appeared to be a brand new board when I installed it and was in a LG service parts box. When I replaced the board it was no longer singing but only the plasma would glow no picture, no menus. I noticed the status leds had now changed slightly. D2 - off D3 - on D4 - on D5 - off. No picture so I went back to reinstall the old Ysus board. Noticed it was still singing but the status LEDS blinked at first for a second or two as they origionally looked then went to status like the new board and the ysus was still singing. I tapped the singing IC gently and it seemed to stop singing. I then noticed the Zsus was slightly singing. Could have been singing quietly the whole time and we didn't know it. Boards do not seem to sing when new ysus is installed.

I just don't know where to go from here. Do I replace the main board? LGCMx05W? That was my next thought but want to make sure I'm not missing anything stupid. I've fixed a couple so far and replaced capacitors on LCD monitors but this is the first plasma I've looked at. Also has anyone written a basic for dummies plasma/lcd repair guide to troubleshoot which boards might cause what types of symptoms. Your help is greatly appreciated and I'm hoping this is something simple and easy.
Nathan

[Webwaster]

This is the reply I got from Sanyo:
There is a panel self test for this panel. It eliminates the Main Bd. during the test. Unplug the LVDS cable from the Main to the Control Bd. behind the Main. Short the two pins in the attached jpg file. If the self test works OK, the panel will have several internally generated patterns on the screen.

D2 & D5 = off
D3 & D4 = on
for a working TV


Just wondering which is the LVDS cable is this the flat ribbon cable?

[Webwaster]

Plugged tv back up to try and do the short thing and now status leds are as follows no matter which oard is installed:
D2 - off D3 - on D4 - off D5 - on

[Webwaster]

BW Figured out the LVDS is the cable that goes from the board with the inputs and tv tuner on it to the Logic board, right?

[PlainBill]

Originally Posted by Webwaster

This is the reply I got from Sanyo:
There is a panel self test for this panel. It eliminates the Main Bd. during the test. Unplug the LVDS cable from the Main to the Control Bd. behind the Main. Short the two pins in the attached jpg file. If the self test works OK, the panel will have several internally generated patterns on the screen.

D2 & D5 = off
D3 & D4 = on
for a working TV


Just wondering which is the LVDS cable is this the flat ribbon cable?

It's usually a round cable. I just checked, there does not seem to be a service manual available from Sanyo. Rather than crossing to similar LG TV, let's do this the easy way.

Notice my signature. Follow the link for instructions on ATTACHING a picture, and read them. Take two pictures of the back of the TV with the cover removed. The first should show the entire TV. The second should show the 'main board'. This is the board that contains the tuner and all the video connectors. Attach the pictures to your next post and I can point out the cable.

PlainBill

[Webwaster]

Attached is the panel service manual. I will attach photos as soon as I can shoot them and get them off the camera.

[Webwaster]

Ok, plugged in this evening and was back to the GOOD setting D3-D4 ON D2 & D5 OFF. I noticed the ribbon cable attaching the Ysus to the logic boar appears to have one connector that is somewhat rubbed on the end of the ribbon. I think this may be part of my issue. Back to origional Ysus board and lights are at good status. No really singing like it was just a simple little purr almost. Not as loud as the fan in my monitor.

Now, after disconnecting the LVSD cable I shorted pins 1-2 win an insulated phillips (couldn't find a small enough jumper here at the house or one of my standard insulated in my truck) Kinda scary because I was micrometers away from shorting pin 3 although don't know what it might have done. Panel is good and going through a diagnostic test Goes to bw cross, then goes through each color, does some boxes across the screen etc. Didn't have it by a mirror so was looking over the top but everything SEEMS fine there. So, I've got a good panel and since it's sending the diagnostics across the screen that would mean my drivers, V-SUS, Z-SUS, Inverter are all good, right? Also not sure however if this test actually tests the logic board or not. Sanyo tech says "It eliminates the Main Bd. during the test." Does this mean my problem lies in the main board of this tv? If so any suggestions about what might go wrong on the main board to test first.

[PlainBill]

Originally Posted by Webwaster

Ok, plugged in this evening and was back to the GOOD setting D3-D4 ON D2 & D5 OFF. I noticed the ribbon cable attaching the Ysus to the logic boar appears to have one connector that is somewhat rubbed on the end of the ribbon. I think this may be part of my issue. Back to origional Ysus board and lights are at good status. No really singing like it was just a simple little purr almost. Not as loud as the fan in my monitor.

Now, after disconnecting the LVSD cable I shorted pins 1-2 win an insulated phillips (couldn't find a small enough jumper here at the house or one of my standard insulated in my truck) Kinda scary because I was micrometers away from shorting pin 3 although don't know what it might have done. Panel is good and going through a diagnostic test Goes to bw cross, then goes through each color, does some boxes across the screen etc. Didn't have it by a mirror so was looking over the top but everything SEEMS fine there. So, I've got a good panel and since it's sending the diagnostics across the screen that would mean my drivers, V-SUS, Z-SUS, Inverter are all good, right? Also not sure however if this test actually tests the logic board or not. Sanyo tech says "It eliminates the Main Bd. during the test." Does this mean my problem lies in the main board of this tv? If so any suggestions about what might go wrong on the main board to test first.

Well, there are three possibilities. One is that the problem is the tiny fraction of the main logic card that interfaces the LVDS cable to the rest of the circuitry is bad. The second is that the LVDS cable itself is bad. The third possibility (and most likely) is the main control board is bad. If you have a scope you could look for signal activity on the main board end of the cable. Going beyond that on on the main board without a schematic is difficult, but not impossible.

There are a number of voltage regulators on the main board. If one of them is bad, it could cause the symptoms you see.

Now you know what comes next - good quality 2000 x 2000 pixel pictures of the main board, top and bottom.

PlainBill

[Webwaster]

As soon as I get off work I'll pull the main board and take good photos of front and back. Thanks again Bill for all your help so far.

[crepiduse]

If you're still around, what pins did they get you to short out? can you attach the image?

[JIMH]

[QUOTE=crepiduse;141500]If you're still around, what pins did they get you to short out? can you attach the image?[/QUOTE

Hello Everyone,

I too should be most interested to hear which of the two LVDS connector’s pins must be shorted together.

Many Thanks,

Jim, in Madrid, Spain.]

[JIMH]

Hello Everyone,

I too should be most interested to hear which of the two LVDS connector’s pins must be shorted together.

Many Thanks,

Jim, in Madrid, Spain.

[JIMH]

Hello Again,

RE: MY MESSAGE <<< Hello Everyone, I too should be most interested to hear which of the two LVDS connector’s pins must be shorted together >>>

At almost 79, it seems I’m getting too old for this racket for I’ve only NOW just noticed a previous missive, which states:

<<< Now, after disconnecting the LVSD cable I shorted pins 1-2 win an insulated Phillips....>>>

With Best Wishes to All and sincere apologies for my appalling lack of intellectual acuity.

Jim, in Madrid, Spain.

[phatcav]

I'm currently working on the same model - it has the same symptoms - all voltages look ok on the power supply - when the tv first comes on the panel flashes briefly then just glows and I have audio - when changing thru the channels i can hear it changing just no video. I was wondering if you tried to replace that main logic board and what the outcome of that was? I've fixed a bunch of lcd tvs and this is the second plasma i've worked on they are a little different beast thats for sure.

thanks

[PlainBill]

Originally Posted by phatcav

I'm currently working on the same model - it has the same symptoms - all voltages look ok on the power supply - when the tv first comes on the panel flashes briefly then just glows and I have audio - when changing thru the channels i can hear it changing just no video. I was wondering if you tried to replace that main logic board and what the outcome of that was? I've fixed a bunch of lcd tvs and this is the second plasma i've worked on they are a little different beast thats for sure.

thanks

Note post #7. If you short pins 1 & 2 of the LVDS cable you put the Main Logic Card in self test mode. If the panel runs through a series of test patterns you know the panel, sustain cards, buffers, etc are all good. If (as is likely) you get nothing, you have a problem with one or more of the above.

PlainBill

[phatcav]

My power board looks a little different than the one mentioned in post #7 -
but the main logic board looks the same - I'm trying to figure out which cable is the lvds cable to short the pins on. Any help would be appreciated!

[PlainBill]

Originally Posted by phatcav

My power board looks a little different than the one mentioned in post #7 -
but the main logic board looks the same - I'm trying to figure out which cable is the lvds cable to short the pins on. Any help would be appreciated!

It's the cable that runs from the main control board to the main logic board.

PlainBill

P.S. I've just skipped by 5 posts where the poster expected help, but couldn't be bothered to attach a picture. This was almost #6.

PB

[phatcav]

Ok i got some pictures now :-) i had to get new batteries. They pictures arent the best quality so hopefully you can assist with these pics? Any help would be appreciated!

Thanks,

[PlainBill]

Originally Posted by phatcav

Ok i got some pictures now :-) i had to get new batteries. They pictures arent the best quality so hopefully you can assist with these pics? Any help would be appreciated!

Thanks,

Ahh, much better. The cable outlined in red should be the LVDS cable. It goes to the main logic card, mounted behind the chassis holding the main control card.

PlainBill

[phatcav]

Am I supposed to short the pins on the cable connector or the board connector? I'm thinking the board connect since PIN1 on the cable is not utilized - PIN1 is the first pin on the lower left hand side of the cable and pin 2 is the pin right above it on the top row and it is pinned. I just want to make sure before i start jumping them. Thanks so much for the help up to this point btw.

Thanks,
phatcav