LG 50pj350 plasma not powering going to standby

[cequil32]

Re: LG 50pj350 plasma not powering going to standby

Well the new boards did not correct the problem. I put a new Ysus board in and a Ysus bottom buffer. When I turned it on it made a loud chattering noise and kicked off. It reset and tried to power on again but this time as I was looking at the front of the tv I heard a loud pop. Now it is back to the same situation I was in before, the power supply will only run if the Ysus is unplugged, but all other boards plugged in. Could this be a power supply problem, won't power under load maybe?

[tom66]

Re: LG 50pj350 plasma not powering going to standby

You probably got a bad y-buffer or y-sus. It happens.

[cequil32]

Re: LG 50pj350 plasma not powering going to standby

So where do I go from hear? Send the Ysus board back or is there a way to test if I have a bad one out of the two I have easily. They sent me two of the lower buffer boards and not one of the upper, I have requested the upper. Could the upper being bad cause this?

[tom66]

Re: LG 50pj350 plasma not powering going to standby

Yes, quite easily.
A bad lower buffer can damage the Y-sustain.
A wounded Y-sustain can damage both buffers.

[cequil32]

Re: LG 50pj350 plasma not powering going to standby

Replaced boards and it fired up. Now there is a black line on the bottom all the way across about an inch or so from the bottom? Is those an x driver board or the panel itself?

[tom66]

Re: LG 50pj350 plasma not powering going to standby

From top to bottom: Dud plasma panel if single line or bar ~1" or bigger.
From left to right: Dud plasma panel (only if single line or small cluster) OR Y-Buffer FFC is not seated properly.

[djluis]

Re: LG 50pj350 plasma not powering going to standby

It looks like this model is very sensitive to damage the YSUS board, I am working on one and damage the YSUS board 3 times. So it looks like the 3 boards should be replaced 2 buffers plus the YSUS.
Now if someone have enougth experience with this model, can I turn TV on without the buffer boards, so I can measure VSC, VY, and other voltages generated by the YSUS board?

[tom66]

Re: LG 50pj350 plasma not powering going to standby

Yes, it can be run without the buffers.

[djluis]

Re: LG 50pj350 plasma not powering going to standby

I have repaired several of this models in 42 and 50 inches, but obviously when I checked the buffers there were low readings from the floating and VSC.
This particular one the buffers doesnt have low readings is upper on the 300k ohms. But as soon I replace the YSUS it damage the YSUS shorts some transistors. I have invested a lot of money with this unit not worth the time spending also. I will order the transistors and will try to repair the YSUS, and in the near future will post results.

[zachstanley]

Re: LG 50pj350 plasma not powering going to standby

I am having a similar problem with this TV. When I try to turn the TV on, a relay clicks. I hear a slight chirping tone that goes from low to high pitched. Then a relay clicks and everything turns back off. Never any picture, etc. I bought the TV used, and it appears someone may have already done the power supply repair that is available for this TV. Tested (on the power supply) all diodes, fuses, resistors, etc (except the SMPS Current Mode Controller 3BR1565JF, because I'm not 100% sure how to test this transistor). The fuses on the Ysus and Zsus are also fine, although I have not done extensive component testing on those boards.

I've been referencing this manual:


The troubleshooting I've done so far:

All boards plugged in:
M5V (bias to Ysus): 0V initially. I try to turn TV on and relay clicks, goes to 5V while chirping (low tone, high tone), click and 5V disappears
Va: 0, slight (<1V) bump when I try to turn on, then 0
Vs: 0, approximately 1.5V bump when I try to turn on (meter probably just doesn't react quick enough to measure), back to 0
Vy: 0 constant
Vsc: 0 constant
Standby: 5.22V, down to 5.17V when I try to turn on, returns to 5.22V

Zsus unplugged:
Same as before. I try to turn the TV on, a relay clicks. I hear a slight chirping tone that goes from low to high pitched. Then a relay clicks and everything turns back off.

M5V (bias to Ysus): Same behavior as before
Va: Same behavior as before
Vs: 0, approximately 3.5V bump (again, meter probably just not quick enough), back to 0
Vy: 0, tiny fluctuation (<1V), back to 0
Vsc: 0 constant
Standby 5V: 5.22V, down to 5.17V when I try to turn on, returns to 5.22V

Ysus & Zsus unplugged:
Much different behavior. I try to turn the TV on and a relay clicks. I hear a very faint clicking coming from the center of the power supply. Everything seems to be stable. When I try to turn the TV off, it takes a couple seconds but eventually a relay slowly clicks and everything turns off (including faint clicking noise).

M5V (bias to Ysus): 0V initial to 5.22V after I try to turn on. Stays at 5.22V.
Standby 5V: 3.46V initially (expected voltage). Try to turn on TV, goes to 5.17V and stays there. Returns to 3.46V when I turn off TV.
Va: 0V initially. Try to turn on TV and it goes to 59.8V and stays there (expected voltage). Returns to 0V when TV turned off.
Vs: 0V initially. Try to turn on TV and it goes to 204V and stays there (expected voltage). Returns to 0V when TV turned off.


Does it sound more probably that the power supply is failing under load, or that my Ysus or Zsus board has a problem?

Appreciate any help, I love this site!

[zachstanley]

Re: LG 50pj350 plasma not powering going to standby

No thoughts? Anyone? Bueller? I'm down to try anything! It's a learning process for me all the way.

[johnboy1313]

Re: LG 50pj350 plasma not powering going to standby

You'll have better luck starting a new thread.

[zachstanley]

Re: LG 50pj350 plasma not powering going to standby

I tried initially, but was told I couldn't start new threads because I didn't have a high enough post count. I'll try again...