LG 60PV450 Sound No Picture

[Secondhandcash]

I have an LG 60" Plasma (60PV450), this was a curb find with bad sustain boards that were repaired over 8 months ago, never had an issue until today.

TV now turns on and I can here sound with no picture, front status LED light slowly dims away within 2-3 seconds after TV turns on (can't remember if that is normal). Things I have already checked

1. Vs and Va voltages are ok (listed as 201/55 my checks 200.8 and 55.3)
2. Checked all fuses on X&Y Sustain boards, Power Supply Board.
3. Removed LVDS cable and jumpered controller board NO PATTERN
4. Checked connector between main board and power supply and I have one voltage (3.3V MST) that is coming out at 5.1V

Was hoping something here might grab someones previous experience and point me in the right direction.

[tom66]

Re: LG 60PV450 Sound No Picture

On the Y-sus locate the two resistors marked -Vy and Vsc and check voltage across them, should be approx -200V and 150V

[Shinju]

Re: LG 60PV450 Sound No Picture

This panel is my bane right now Subbed, if I can help I will pipe in too. I have 2 of these one works flawless the other well major issues

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

Tom just want to make sure this is what I am looking for (in pics)? And I assume Fluke on DC and measure across those test points? If so I get:

Vsc 2.7V (fluctuating)
-Vy -69.7 (fluctuating)

Way off unless my testing is incorrect.

[Shinju]

Re: LG 60PV450 Sound No Picture

Those are very low voltages (I am also seeing low voltage on both Y/X, those are the correct test points. what is your VZB reading on your Xmain?

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

I am reading 110.6V on the VZB test points.

[Shinju]

Re: LG 60PV450 Sound No Picture

Your Xmain seems to be ok, that reading is inspec of the panel sticker assuming its like mine 110.

Sounds like your Ysus is toast, one other thing you can do is pull the Y driver upper and lower buffers out of the circuit and see if maybe those are dragging the voltage down on your Ysus.

Make sure if and when you pull then that you remove the small ribbon cable at the bottom of your Ysus and the buffer.

With mine I was getting a picture (test patterns with horrible noise in the picture) but I slipped a probe and now I get top half for a second and panel shuts down.

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

With the buffers pulled out of circuit the Vsc is registering 0.012V and the Vy has jumped up to about -130V. I am guessing you are talking about the small ribbon cable on the bottom going into the bottom buffer from the Ysus board?

[Shinju]

Re: LG 60PV450 Sound No Picture

With the buffers pulled out of circuit the Vsc is registering 0.012V and the Vy has jumped up to about -130V. I am guessing you are talking about the small ribbon cable on the bottom going into the bottom buffer from the Ysus board?

Correct, yeah I think your Ysus is toast. do you know how to check for shorts on your ydrive buffers?

[tom66]

Re: LG 60PV450 Sound No Picture

Is that both buffers out, all connections undone except orange ribbons?

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

Tom that is correct, although I went a step further and removed them entirely (disconnected ribbon cables). I am familiar with the process of checking shorted buffers, which I hope these are not as I ordered both new from shopjimmy in September, but if the Ysus board is bad I guess these new buffers may have fried.

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

With those low voltages gentlemen, can I assume the Ysus is fried?

[tom66]

Re: LG 60PV450 Sound No Picture

Would seem so

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

Shinju and Tom66 I replaced the YSUS board after receiving the first one that was destroyed. With the top buffer board installed and no cables connected to the lower board I can get a test pattern from top half of screen, although pixelated. When I connect the bottom buffer I get no picture at all. There is a burn mark on the chassis behind the lower buffer board so i would assume that is what blew and then took out the YSUS board. With the top board only attached I have -178 on my -VY and about 214.6V on my Vsc on the YSUS board. Is it possible that the panel itself is shorted out when the bottom buffer blew?

[Shinju]

Re: LG 60PV450 Sound No Picture

what Ysus model do you have? If you got soot on the panel from a bad lower buffer then its shot and I would not attach it anymore as you might damage the Ysus.

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

This is the pic of the damaged board I received but should work for ID purposes.

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

I forgot to mention that I have installed a new set of buffer boards, well pre-owned.

[Shinju]

Re: LG 60PV450 Sound No Picture

gotcha, so you already installed the new (used) buffers and when they are both connected you are not getting a picture and with only the top buffer attached you are only getting the top half of a picture?

Did you test the buffers for shorts before installing them?

Also your Ysus is Part Number EBR73561201
MFR Part Number 1 LG EBR73561201
Board Number(s) EAX64232001
Panel Sticker Number PDP60R30110

[Secondhandcash]

Re: LG 60PV450 Sound No Picture

In hindsight no, I just tested it and low and behold the bottom one is shorted. If I am testing correctly, I am using my Fluke 87 III Ohm setting black on one pin of the middle connector (P212) and starting at the top of the ribbon cable connector following it from top to down like a zipper with the red lead. The top connector (P201) is showing shorts on about 6 or 7 different pins. The remaining 3 ribbon cable connectors all test OK.

[tom66]

Re: LG 60PV450 Sound No Picture

In hindsight no, I just tested it and low and behold the bottom one is shorted. If I am testing correctly, I am using my Fluke 87 III Ohm setting black on one pin of the middle connector (P212) and starting at the top of the ribbon cable connector following it from top to down like a zipper with the red lead. The top connector (P201) is showing shorts on about 6 or 7 different pins. The remaining 3 ribbon cable connectors all test OK.

Yep that's dead. No cracks on the panel? Is original OK?