LG 50PV450 Have sound but no video

[unixmonkey]

I have an LG 50PV450 that recently died on me (about 5 months ago). It's been sitting on my couch in the basement since then and I've finally gotten the ambition to look at it. When it turns on, I can hear the sound like normal, but I have no video. I've turned it on in a dark room, and there's nothing at all. I've skimmed some posts and have tried the following:

I've tested the fuses, they're all fine
All the capacitors are fine (no bulges)
I've disconnected the Y buffers and connected the top only, and then the bottom only (while keeping the middle ribbon connected), no change
I've tested the voltages:
Va - I was getting a reading a few days ago, but I forget what it was. Since disconnecting the buffers and re-connecting them, now I get nothing.
Vs - I was getting a reading a few days ago, but I forget what it was. Since disconnecting the buffers and re-connecting them, now I get nothing.
-Vy - This seems to be different every time I try to get a reading. Sometimes it starts at 20v and builds up to 500, and sometimes it hovers between 150 and 190.
Vsc - This reading was steady, but I think it was about 5 or 6 volts above the sticker.


Any suggestions on where to continue for troubleshooting? The voltages seem weird. It's possible that I'm not doing it right. I'll check them again tonight to confirm and update with the voltages that I get.

[sordids999]

Re: LG 50PV450 Have sound but no video

Posting pictures of the back of your tv showing the boards with clear pictures may help you more with fixing your problem

[unixmonkey]

Re: LG 50PV450 Have sound but no video

My apologies. I thought I had attached them.
Here they are. Let me know if I need to post better ones.

[Andrew F. Ali]

Re: LG 50PV450 Have sound but no video

On P813 see if you have 5Vstby on Pins 13 & 14
If you do then you can Self Test the Pwr Bd as follows:
A. Make test-bulb ( Connect two (2) 120V 60W in series)
B. Disconnect P811 and P813
On the underside of the Pwr Bd on P813:
1. Connect Pin18-Auto Gnd to Pin10-Gnd with a wire
2. Connect a 100ohm resistor across Pin14-5Vstby and Pin17-M-On
3. Connect another 100ohm resistor across Pin15-RL-On and Pin13-5Vstby
C. On the underside of the Pwr Bd on P811:
4. Connect the Test-bulb across Pin4-Gnd and Pin1-Vs Supply
D. Check all connections are properly made and insulated from each other
E. Plug into 12Vac and observe
5. The Test-bulb should light up bright (Vs Supply GOOD)
6. Measure P811 Pin6-Va=55V
7. Measure P811 Pin7-M5V=55V
8. Measure P813 Pin1 or Pin2-17V
9. Measure P813 Pins 5,6&7-5V
10. Measure P813 Pin8 (Error Det)-4.9V
11. Measure P813 Pin16 (AC Det)-4.9V