LG 50PC1DA - Clicking not as simple as I thought

[tom66]

Symptoms:
- Inrush relay clicks
- Vs/Va start rising slowly
- Vs/Va collapse slowly
- Relay clicks back off

Tested/replaced:
- AC Detect is good
- IPMs are good (while Vs is rising and falling, the waveforms are there.)
- All bad caps (at least 10) replaced
- Several non bulgers replaced
- C855 blue poly cap replaced
- Main board is leaving control signals on
- Panel temperature is OK

Next step is to check the microcontroller inputs -- something may be awry there. Seriously wish LG released a schematic of this PSU.

Have a spare mainboard will consider swapping it.

Right now though, am drawing a blank...

[ron77]

Re: LG 50PC1DA - Clicking not as simple as I thought

Looked at this thread yesterday.Could not think of anything that could be helpfull.This morning, however, remembered had similar fault on phillips plasma.I will tell you the symptoms and cure,but fully aware your knowledge of plasma is very good. Vs, va rose slowly, but could not reach their correct voltages. The vs though stuck on 54v. By heating the psu got vs up to 80v quickly enough, to stop it collapsing. There was no fault anywhere on the psu other than capacitor on 9v rail, part of the stby secondary circuit. Probably won't help you, but is sort of similar to to way your tv is performing. Ron77.

[tom66]

Re: LG 50PC1DA - Clicking not as simple as I thought

Hi Ron. I actually just fixed with a friend the Philips PSU you talk of. Bad cap on 9V rail. Though that one was throwing 2 blink error. We've nearly replaced every cap on the PSU...

[tom66]

Re: LG 50PC1DA - Clicking not as simple as I thought

OK... Now, with some tweaking of Vs/Va, the plasma panel powers up... yay...

Not so hopeful though. While it does light, we only see occasional flickers of grey.

Eventual diagnosis found:
- ER IPM to be failed (but NO obvious shorts; it is breaking down) Burning smell and arcing noise heard from device.
- SUS IPM to be suspect (believed good but cannot rule it out)
- All but the bottom two buffer ICs to be fried (10 out of 12 with dead output lines)

The repair has been determined to be uneconomical for now, as it will cost well over £130 to fix.

[flocko]

Re: LG 50PC1DA - Clicking not as simple as I thought

Hi Tom what did you find on the power board to get the vs to come up faster? On my board by the time Vson hits 4.9v the relay has already dropped out, Got more caps on the primary side to change when they get here,there are lots 50PC1DA down this way with damaged screens the most that i pay for them is £15.

[tom66]

Re: LG 50PC1DA - Clicking not as simple as I thought

Hey if you get a cracked screen 50PC1DA I'd be interested in the Y-sustain and buffer boards.

Vs/Va needed a tweak to the pots... not sure why but both were at extreme minimum, tweaked them to rated voltage and the panel began sustaining (voltages stayed up, relay didn't click off.)