lg 42pc1da sound but no picture

[rdsx18]

Hi all, new here but I have a 42" LG plasma that I got for nothing, it made a loud pop and he picture went on it. I did some troubleshooting but nothing too crazy because I have limited electronics repair experience. The y-sustain had a blown fuse and cold heat sinks after leaving it on for 20 minutes. So, I replaced the y sustain and buffer but it is still the same. The x sustain was replaced in 2010 and the tv hasn't been used since it broke in 2011 so I don't think that's the issue. All fuses are still good, I checked those, but the board on the center back has a few green leds and one red one, d1303. Sorry for the long post but any ideas? Could the y sustain I got be busted too?

Cliff notes: replaced x sustain, y sustain, y buffer and still no picture.

[Alastair E]

Re: lg 42pc1da sound but no picture

Highly likely the 'new' sus board has a popped IPM too They have come to that age when they are failing, and most popular item to go is either of the two IPM's on the SUS boards.

IPM type is-- YPPD-J018C/E ....

Check through past posts on that model for testing info to check it out.

[rdsx18]

Re: lg 42pc1da sound but no picture

Thank you for the response, I just tested the ipm on the old y board, it was toast. He new one however is fine, could the x board be gone again too? What else would cause no picture but maintain sound? I was under he impression it was a y sustain issue

Edit: I'm sorry, I keep saying x sustain for some reason, I mean z.

[Alastair E]

Re: lg 42pc1da sound but no picture

The IPM's dont always go short-circuit!

The MOSFETS can first short--Then blow Open circuit, (Happens almost instantly) so a fault wont show on simple meter testing.
They can also fail, when the MOSFETS just go Open-Circuit, no pops, no bangs or drama, just stop working.

It/They can still be faulty unless tested properly dynamically--after removal, using 12-24V and a regulated 15V supply, running a 50W lamp as load, and input of square-wave around 50KHz, scoping output to test properly.
--This is how I test 'em anyway.....

There are Many reasons Why a PC1DA wont have a picture, but still have sound--the IPM's are the most popular reason however.

How are all the other voltages derived on the Y-SUS and the VZbias on the Z-SUS?

Anything on the screen At All--? in a darkened room?

Vs and Va from PSU OK?

Start at basics and work through--Only way is by logical testing, start by testing ALL the supplies from PSU And then the ones on the Y-SUS like the -Vy etc and Vzbias on Z-SUS...

Changing boards randomly is pointless and expensive, will only cost you too much and generally isnt worth the effort when you consider most vendors don't/cannot/unable to/couldn't care less whether the boards they sell are OK.

[rdsx18]

Re: lg 42pc1da sound but no picture

I'll have to start testing the voltages more, but the old y sustain shorts between the vs out and some pins so I at least know that was for sure bad.
Thank you for your help so far.

[Alastair E]

Re: lg 42pc1da sound but no picture

Its a fair assumption that the replacement Y-SUS has a fault.

Its unlikely--but conceivably possible-- that the Z-SUS IPM or the Z-SUS board has failed At The Same Time as the original Y-SUS IPM shorted.

[rdsx18]

Re: lg 42pc1da sound but no picture

Just tested vs and va from psu, it is 186.6 and 59.8 respectively. I'm sorry but I have no idea how to test vzbias, and all the screen does is occasionally white spots when in a dark room, no picture at all

[Alastair E]

Re: lg 42pc1da sound but no picture

Right--OK....

Here is a Service-Manual download site that Tom66 hosts from this Forum.

Check through the list of PC1DA stuff, download the S.M. and Guides, have a look through, they'll say how to check the other voltages etc--

http://www.tgohome.com/ServiceManual...h=Submit+Query