My first plasma, RCA 42PA30RQ - Sound but no picture

[lookimback]

This is my first plasma but I've been reading all about them. Also, Tom's tutorial has helped me a lot. This particular one seems like a good first because there are a lot of threads here on it already.


I haven't checked myself but the person I got it from said that the picture went out but he still had sound. I get a double click and a blue light when I turn it on. More of a click clack. Then the same when I turn it off.


So on the Y buffer I have 3 diodes (D5400, D5401, D5403) which I get about 3 ohms across. Removed from the board they are fine. I'm just guessing that this isn't normal. I removed IC U5401, not the problem. I'm pretty certain that the PN096S3s are the problem, I've ruled everything else out. But that only takes care of the Y buffer.

I noticed that I get a slight hum from the X main if I have the Y buffer removed but not if it's in. I don't get a hum from the Y main at all. I haven't checked for voltages yet but that's my next move.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Ok, it makes a difference whether or not the panel is connected. With it connected I get the 3 clicks like everyone else.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Samsung panel? Look at the LED on the control board. Middle board which the main A/V connects to. The LED should blink once a second or every two seconds (normal) or about once every 5 to 7 seconds (fault). What does it do?

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

It was once every 5-7 seconds. I just found and removed 2 shorted mosfets from the X main. They are both marked RJH30E2. No other shorts on the X main. With only the X main unplugged I get 207v on VS and VA 54v.

I can find no faults on the Y main and I think it might be OK.

What do you think about the Y buffer? Is it normal that I would have low resistance across those diodes I mentioned in my first post? Or should I suspect the PN096S3 ICs could be bad?

Yes, it is the Samsung panel BTW.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Can you post a picture of those diodes? IIRC, they usually have some low resistance in parallel with them, they are for VSCAN circuit energy recovery I think.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

I'll take them right now. Give me a few minutes and I'll post them. Thanks.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Here's the pics. I got one good enough that you can read the numbers. They all have the same P/N.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Yes so you can see the big 22R resistors in parallel so a low resistance reading is expected, 3 ohms is a bit too low, would expect around 11 ohms.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Ok, so something must be shorted. I'll pull the resistors first. After that nothing left but the PN096S3 ICs. Thanks.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Ah, wait a second, how many pairs of Rs? 3 pairs 2 each, they are all in parallel, there's your 3 ohms right there. Those Rs/Ds are only in SERIES with the VSC_H voltage, so the ICs going should would not cause that fault.

I'd look straight back at that X-main. Repair kit available...

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

3 pairs. 22 divided by 6 would be 3.66. I just rechecked and I have 3.8 ohms. So I guess I'm good. The difference is probably my test leads. I ordered 50 of the RJH30E2 and RJP30E2 mosfets from China just now. I'll sell the extras in my Ebay store.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

...and the non zero tolerance of real world resistors.
I'd also check the gate driver IC near the IGBTs and in general replace it anyway due to the likelyhood it has been "wounded" by the failure.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

That's on the X main or the Y buffer?

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Here's the bottom of the X main. Can you point out the gate driver IC you're talking about please? Thanks.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Which FETs are bad? It's one of the 8 pin SMD IC near the bad pair of FETs.

[tw2005]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

I made a feeble attempt with one of these xmains. Did the IGBTs only and they blew straight away. I gave up trying to identify those SMD parts, the board was so cheap.

Did the x & y swap, x damaged the y with all my fiddling.

buffer was ok , and fixed. that was a samsung same panel as this.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

There was one bad on each end. I removed them before taking this pic. If you zoom in you can see where they were.

[tom66]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

I'd look into replacing these devices too then.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Here's closeups of the ICs. The 2 on the right I'm pretty sure are FAN73711.

The one on the left, not so sure but maybe FAN73611?

Digikey has both if that's what they are.

Datasheets for both are attached.

[lookimback]

Re: My first plasma, RCA 42PA30RQ - Sound but no picture

Ok I just noticed your last post. The one you circled on the left is marked 5K. I'll try to figure out what that is.