This guy has an RCA 42PA30RQ

[Bling23]

Re: This guy has an RCA 42PA30RQ

The boards LED flashes on for about five seconds and goes off for 2 seconds. but what am i looking for with this test? waveform after hooking the jumper wire?

[tom66]

Re: This guy has an RCA 42PA30RQ

You're looking for a Y-main waveform yes, and when you hook up all the boards (except the X-main) you should see dim test patterns cycling on the display panel.

[Bling23]

Re: This guy has an RCA 42PA30RQ

I should hook up the Y-Buffer board back up ?

[tom66]

Re: This guy has an RCA 42PA30RQ

For the first test (waveform) leave it unplugged.

[Bling23]

Re: This guy has an RCA 42PA30RQ

ok this is how i hooked the jumper wire. LVDS ribbon disconnected. So no change.. when I turn on the TV I get a quick waveform and then it flat lines. it happens to fast to get a snap shot

[tom66]

Re: This guy has an RCA 42PA30RQ

The problem I have is I had a PS43D450 to repair and it would shut down with the X-main failed or missing. This made it hard to isolate the fault. BUT, an older PS42B450 did let me run with the X-main missing, and I'm fairly sure this TV is based off the same plasma panel. As far as parts go, what have you already replaced?

[Bling23]

Re: This guy has an RCA 42PA30RQ

I've replaced the Y-Main the Y-Buffer and I have the X-Main on order and a small square board that has input from PSU output to main board.

[tom66]

Re: This guy has an RCA 42PA30RQ

Can you try the original Y-main? Was that definitely bad?

[Bling23]

Re: This guy has an RCA 42PA30RQ

Four of the 8 mosfets were shorted. I tried replacing them on the board but I'm need more work with my soldering skills hahahaa

[Bling23]

Re: This guy has an RCA 42PA30RQ

I still have the board but I removed the heat sink and the mosfets

[tom66]

Re: This guy has an RCA 42PA30RQ

Ah OK then. Perhaps re-try the test for the shorted FETs on the new Y-main?

[Bling23]

Re: This guy has an RCA 42PA30RQ

I have a question regarding that?... Can the test be done with fets on the board or is it best to have them out of circuit? Also is it better to use diode on DMM or use analog multimeter?

[tom66]

Re: This guy has an RCA 42PA30RQ

You can do it in circuit. Once you find a suspect device pull it and re-test. Diode mode works well. No need to use an analog meter.

[Bling23]

Re: This guy has an RCA 42PA30RQ

All the diodes tested fine. I had one that would not register any forward voltage drop on my fluke 87. I removed it out of the curcuit and retested it and it tested good. It's a RJP30E2

[tom66]

Re: This guy has an RCA 42PA30RQ

That's an IGBT.

[Bling23]

Re: This guy has an RCA 42PA30RQ

I found a good Samsung training Manuel online. It explains how everything is suppose to work with each board. My PSU voltage is key to determine what's going on. I think something is powering down the PSU. That fuse located near the VC input on the PSU reads 120v when I plug in the TV. When I power on the TV, the volts drop to 64 volts. Shouldn't that maintain a constant 120?

[tom66]

Re: This guy has an RCA 42PA30RQ

More than likely it is due to the class Y caps. If the PSU voltages are good, if only transiently, the fuse is almost certainly good.

[Bling23]

Re: This guy has an RCA 42PA30RQ

I wish I had schematics for this TV.

[tom66]

Re: This guy has an RCA 42PA30RQ

I have schematics for the PSU, I think.
http://www.tgohome.com/ServiceManual...&Search=Submit

[Bling23]

Re: This guy has an RCA 42PA30RQ

So far I"m below $100 in replacement parts...I wonder if I should order a logic board