Samsung PN58C500G2FXZA - Sound but no picture

[DLinkOZ]

I have this 58" Samsung plasma, and it's my first time to attempt a repair on them. I've read through the fast track troubleshooting manual for it, but I'm unsure of the cause (none of the scenarios are true, and the SMPS seems to be powering down). I think perhaps the x-sus, since that voltage appears to be suspect and the manual states the x-sus generates it. Pics are below - they're with my phone and not great, I can take better if necessary. The last shows the two test points I used to measure Vsc and Ve.

Here are my power readings:

Vs: 210v at power on (exactly what the panel sticker states). It immediately begins to drop quickly, slowing considerably at 20v until it eventually drains completely to 0v.

Va: 55v at power (exactly what the panel sticker states). It immediately begins to drop quickly until it drains completely to 0v.

Vsc: -200v at power on (exactly what the panel sticker states). After ~15 seconds it begins to drop quickly until it drains completely to 0v.

Ve: -40v at power on (panel states 90v, so this is suspect). After ~15 seconds it begins to drop quickly until it drains completely to 0v.

Any input is appreciated. Testing the banks of transistors on the y-sus doesn't show any to be shorted, further leading to my x-sus guess.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Here are the images, I was receiving a 500 error when attempting to attach previously.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Correction - the SPMS is not powering down. You can continue to listen to the TV, so it's obviously staying on.

[martino]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Just curious,I circled that transistor in this picture.Can we get a close up of that,it seems"out of place"??

[martino]

Re: Samsung PN58C500G2FXZA - Sound but no picture

sry,pic didnt load lol

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

That nonsense exists on both sus boards. First two are y, second two are x.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

My Ve is wrong, I'll need to get it plugged back in and capture a proper reading.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

So Ve is good - starts at the proper 90v and, like the others, begins to rapidly ramp down to 0v.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Looking at the pics on shopjimmy, they also show those strange transistors.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

According to this, it may be the y sus or buffer, since I do seem to get a vs power down.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

So I've been trying to determine which sus/buffer set is giving me problems - x or y - and I came across an oddity. See the attached pictures, specifically the second. The connectors from the y sus to the y buffers seem to carry voltage across (in the second, you can see that the bottom half of the pins go into the ground plane on the right). What I've found is on the one of the connectors on each buffer board (upper and lower) shows exactly 31.5 ohms across the sections (assuming it's positive and negative, the latter being obvious since it connects directly to the ground plane on the y sus). So would that point to a short in my y sus/buffer set?

[martino]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Is that with the buffer disconnected from the y main?

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

No, it's with the buffers still connected. I didn't bother to disconnect, as I don't know that I care if it's the buffer or main as I'll be replacing a full set (y main + buffers or x main + buffers). So isolating to either the buffer or main isn't necessary, only determining if it's y or x.

[tom66]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Yes the ground plane is the FLOATING GND node (the sustain board output) and the other traces are the SCAN HIGH voltage. They should be open circuit between those two terminals. (About 140V in operation between them.) If they are not there is a short on the buffer board.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Great, that's what I thought. I'll do the same test on the x side, but with only 31 ohms I can assume I need to pick up a set of y boards. Correct?

[tom66]

Re: Samsung PN58C500G2FXZA - Sound but no picture

No need to test the "X" side -- there is no X-main buffer board.
Check panel for cracks very very carefully before ordering a new board, including ones right around the edge of the screen.

[DLinkOZ]

Re: Samsung PN58C500G2FXZA - Sound but no picture

Will do, thanks!