LG Plasma 50PC1DR- Y-SUS Issues

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I've used m4 10mm screws from the top of the ipm (just drilled the plastic holes in ipm + heatsink a bit bigger) and screwed from the top. perfect !

just one thing im wondering, those ipm's run quite hot do they ? even to hot to touch.. should i add some (maybe 80mm) fans to those units ? is really the heat the cause of their failure ?

i was thinking of adding at least 1 fan on each side of the plasma on the ER IPM.. the one that runs hotter

still one y-sus to fix on that 3-plasma project found a few burnt resistors near the fet that always shorts.. maybe it was just those smd resistors that ive missed that got that thing shorted every time.

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I really have no idea, as I have never replaced an IPM, and plan to avoid it! If you are using any kind of glue, make sure it has good thermal conductivity. Most are very good insulators, making the heatsink less effective... and those IPMs run very hot.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

im having issues with some ipm i fighted with earlier. its got missing traces and its nearly impossible to do a proper job with the heatsink installed.

if im using thermal paste and cyanoacrylate on the black plastic tabs, would you think the ipm heatsink will stay there without falling down ?

crazy glue is pretty strong so on both sides.. maybe even adding a tab of sillicone on 4 sides after it's dried up, on the 4 sides of the heatsink between the heatsink and the pcb... sounds weirdo, or could be ok ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Possibly. You could do a comparative volt meter with your working boards. Check the gate pin of the mosfet.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

so im probably missing something bad around that area on the board..

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Yes. I think it gives it a ramp signal on the gate, which generates the RAMP_UP drive. If it's stuck high, maybe the FET is stuck ON, leading to failure.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

um. the gate drive.. that's the circuit around the fet itself ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Here's where a scope would be handy. I'll bet SUS_OUT is doing something it shouldn't. If SUS_OUT remains high for too long, then the 5 ohm resistance will be shorted to ground by that FET. High current ~40A will flow, frying the FET and resistors. Perhaps somehow the gate drive to the FET is faulty or perhaps the IPM is at fault.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

its the w9nk70z that blows, with the 2 10 ohms smd resistors and another resistor. see picture attached !

well had many issues.. but all were somehow different

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Which chip is it that blows? Didn't you have the same problem with TV #2, and it was a bad IPM that killed it?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

i didnt swap any ipm on the zsus. it seems the ysus is more prone to failure ?

do you have a clue can be causing that w9nk70z chip to blow ? they take away a resistor (smd) and the 2 bigger smd resistor. i've replaced the chip 2 times now from chips from a spare z-sus, but it blows everytime. batch code isnt the same but it seems that it's the good chip..

it seems to be the 'ramp_up' circuit, and it blows right away on tv startup. the ramp_up pot is not working since the circuit is broken, and i have no control on it

i wish i could understand why is that thing blowing !!

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Poor design, you swapped IPM on that one? IPM must kill them every time.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

here's a pic of the z-sus // edit : i see the testpoints didnt search much.. but its still my ysus at fault. i need to understand why it burns again in that section.. the buffer ?

or something else on the board ive missed

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

oh, got it. i swapped a board from a perfect set (zsus) and issue is still there. i noticed the ramp_up can not be adjusted on my ysus, not normal. gonna have to dig more..

checking and again the ramp_up big transistor on right black heatsink is shorted, the 2 10ohms big resistors burned, r66 burned, d28 shorted.

i really dont understand what's burning these things again and again :/

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Can you post a pic of your Z-sustain?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

vzbias ? how do i check this one ?

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

Looks a lot like Zsus. Check Vzbias, should be around 90V.

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

oh well. got this one working as well.. replaced same parts again, dont know what happened, but im having another issue.

what can give this kind of pinkish image ? if i push -yv to -228v or so, i get something better.. but its not in the panel's specs at all

could it be a zsus issue or one of the ipms?

[cheebster]

Re: LG Plasma 50PC1DR- Y-SUS Issues

LOL !! I 'tried' to fix the 3rd one with those parts from digikey. It bang'ed so hard my ear still hurts.. from the ysus board. But there was a picture !! lol. some stuff looks burned, gonna look it up.. but picture was working. hehe

[tom66]

Re: LG Plasma 50PC1DR- Y-SUS Issues

I want to have a recycler who will sell those kinds of things.

Here it's £25 for a 32", and one every 3 months maximum.