Samsung 50" Plasma No Video

[DaveStar]

Its a PN50B450B1DXZA

So here's the rundown of what I've done and where I stand.

Started with no video and no red LED up front but you could here the SMPS clicking. All voltages (PS and Stby are good) as well as Va and Vs. So I assume its not the SMPS.

Disconnected the Logic Board. Would power on and make startup sound but still no video.

Replaced the Logic Board. Same issue.

Vsc voltage on Y main was not good.

Replaced the Y main and Y buffer. Vsc voltage now good but same issue.

Disconnected the X main and it will power on and do the startup sound but still no video.

Replaced the X main. Still no video, but with startup sound.

Vsc and Ve voltage are all over the place but Va and Vs are still good.

I'm hearing a new clicking/ buzzing coming from the Y main and X main.

Any thoughts? I can post pictures and provide more thorough descriptions of what I've done and what is going on.

Thanks in advance for any tips.

[DaveStar]

Re: Samsung 50" Plasma No Video

I really think it is my X main because without the X main plugged in everything checks out OK. With the old X main I get no voltage on Va Vs Vsc or Ve. With the new one, Vs and Va are good but Vsc and Ve are all over the place. Is it possible this 2nd X main board is also bad? Or is it my main control board? That's about the only one I haven't changed out.

[tom66]

Re: Samsung 50" Plasma No Video

Yes, it is quite possible. Can you provide some pictures of your X-main and one of the overall layout of the TV?

[DaveStar]

Re: Samsung 50" Plasma No Video

There is no visible damage to any of the boards. Though all the replacement boards are refurbished.

[tom66]

Re: Samsung 50" Plasma No Video

Your photos are really blurry and it's hard to see what is going on in them. You need to take ones in more light or use a better camera.

[DaveStar]

Re: Samsung 50" Plasma No Video

These are a little better.

[tom66]

Re: Samsung 50" Plasma No Video

They're much better. Thank you.

I've highlighted two measurements to make.
On the 200 ohm range (or just ohms if autoranging) measure between the indicated arcs (board removed, power off.)
When testing to the white connector touch the metal pins.

I'm expecting >10k for both (infinite reading is OK.)

[DaveStar]

Re: Samsung 50" Plasma No Video

I have a cheap multi-meter so I can't set the range, but it is .0L

[tom66]

Re: Samsung 50" Plasma No Video

For both? OK and Ve on the X-main measures what when plugged in and connected?
And autoranging doesn't make your meter cheap. It makes it more expensive...

[DaveStar]

Re: Samsung 50" Plasma No Video

Yes for both, and on both the old and new board. When the old X main is hooked up I get no boot up at all. With no X main the Vsc reading on the Y main is good at -193. When I plug in the new X main both the Ve and the Vsc reading jump up and down but never close to where they should be.

[tom66]

Re: Samsung 50" Plasma No Video

I think the Ve on the X-main has a fault. Both Ve and Vsc are generated on the same supply, so a fault on the Ve (high/excessive loading) will cause problems with the Vsc. At this point I would suggest you have a fault with both boards.

[DaveStar]

Re: Samsung 50" Plasma No Video

Right on, I'll try and send this board back. Do you have any thoughts on buying a refurbished board (this one was) vs a new board?

[tom66]

Re: Samsung 50" Plasma No Video

If you get a refurb board there's a chance someone knows what they are doing and has inspected it for damage and failed components and repaired that. So I'd go refurb.

[DaveStar]

Re: Samsung 50" Plasma No Video

Alright.. New refrurb board just came in and before I put it in I wanted to test the same points you had me test on the old board.

Looks like I'm getting a good reading between the ground and the adapter pin, but ground to Ve is showing overload.

Any thoughts before I install the new board?

[tom66]

Re: Samsung 50" Plasma No Video

Overload? As in a single "1"? That is a good reading. Any other reading you are seeing?

[DaveStar]

Re: Samsung 50" Plasma No Video

Ground to Ve is .0L so over limit

All the adapter pins came in around .7 to .8

I went ahead and installed the board. Vsc is ranging between -4 to -40 volts (should be -193) and Ve starts at 0 and slowly climbs a few mv the longer I hold it on there (should be 89).

I'm curious as to whether their is a problem with my Y-Main now. Perhaps I shorted the replacement one at some point during all this.

[tom66]

Re: Samsung 50" Plasma No Video

What do those voltages do without the X-main installed?

[DaveStar]

Re: Samsung 50" Plasma No Video

With no X main Vsc comes it -192.2, right where it should be.

I have 3 X mains right now, oem, 1st refurb and 2nd refurb. When comparing the 3; ground to Ve all .0L Ground to adapter pins the same on both the refurb boards (.7 or .8) and 0.0 on the oem board. So I think the first board I suspected of being bad was not actually bad but it is nice to have it for comparison right now.

[tom66]

Re: Samsung 50" Plasma No Video

The other possibility is a Y-main failure, due to the combined ERC. Check the ERC to SUS OUT (the ribbon connectors on X-main, buffer connectors on Y-main) and ERC to GND.

[DaveStar]

Re: Samsung 50" Plasma No Video

I count 3 of the 8 boards on this thing that I haven't changed out. Control Main, and a long skinny one that runs along the whole bottom and on behind the control main that connects to the X main.