Samsung Plasma PN50a510p3f

[cliff_hootarski]

Another Craig's List acquisition. Original problem unknown. Former owner replaced the Power Supply, Ymain, Xmain, and Logic board. The TV has a picture but is extremely dim.

Checked all voltages and reset them per panel sticker.

Xmain board heatsinks stay cool to the touch. Ymain heatsinks are heating up normally.

Checked fuses on the Xmain (3) all check good.

Voltage on the row of Caps on the Ymain read 118v,
on the Xmain 103v.

I have all the boards the former owner replaced and have tried to substitute both the old Ymain and Xmain boards. The Ymain shuts down the TV immediately, and I subsequently found a shorted component on it. The old Xmain board exhibits the same symptoms as the replacement board.

It looks like a Xmain board problem. Is it on the board or the controlling voltages from the logic board? The bottom fuse above the logic to Xmain ribbon cable reads 5v on each side.

Should I try another Xmain or can anybody give me a shove in the right direction to get this going?

Almost forgot to mention. I unplugged the LVDS cable and jumpered pins 3-4 on the logic board and got the repeating test pattern, but the picture was still extremely dim.

Two LED's on the logic board flash continuously when powered up.

Also I have done a factory reset in the service menu. (mute 1 - 8 - 2 - power on)

[tom66]

Re: Samsung Plasma PN50a510p3f

We had issues which looked exactly like X-main faults but turned out to be a control board fault -- not sending the correct signal to the X-main. Unfortunately you will need a scope to make tests.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

I do have a scope. However I don't know if it's fully functional. I also have probes X1 - X10 600v rated.

If I can keep a steady hand, I'm willing to try to take measurements.

[tom66]

Re: Samsung Plasma PN50a510p3f

In which case, set your probe to 10X, scope to 5V/div (=50V/div), 10ms/div and trigger on LINE.

Then probe your favourite blue capacitor near the orange ribbons going to the panel, right hand side (pick the side not grounded.)
https://www.badcaps.net/forum/attach...7&d=1368981521

Turn the set on after you have set the probe and scope up. Get an image up: No signal display is ideal as it is static so the waveform won't change.

Post a picture of what you get on the scope.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

I have two scopes, both showing the Xmain output, however the only way I could get a stable image of the output was to vary the scope parameters.

[tom66]

Re: Samsung Plasma PN50a510p3f

Can you try at 1ms/div? Also, it needs to be on DC-coupling.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

Are these any better. Sorry, it's been a lifetime since I had to use an O'scope.

[tom66]

Re: Samsung Plasma PN50a510p3f

Scale of 2V/div (=20V/div at 10X)?

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

That's what the Kenwood scope is set at. Both scopes are on the output of the Xmain, just different caps.

[tom66]

Re: Samsung Plasma PN50a510p3f

Turn the VARIABLE knob until it locks in the CAL position. What is the Tek set at? For that one make sure VAR/CAL is in the CAL position.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

Will do. Just a sec.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

Here are pics of both scope settings. None of the adjustments are out of the "Cal" setting.

[tom66]

Re: Samsung Plasma PN50a510p3f

OK, it looks like your Vs is only 80~100V. Have you checked it is definitely around 200V?

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

Rock steady at 205v measured at the Power supply and the Xmain. Who knows when or if the scopes have ever been calibrated.

[tom66]

Re: Samsung Plasma PN50a510p3f

It looks to me like the scopes are set at 2V? Is this the case?

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

2v/div on the Kenwood.
1v/div on the Tek.
This is the only way I could get a meaningful picture of the signal (that would sync up).
If you want a picture with 5v/div, I will try.

[tom66]

Re: Samsung Plasma PN50a510p3f

Did you have trigger set to LINE or AC?

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

it's deceiving in the pictures, but it is set to line.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

When I fix a couple more of these TV's, I plan on getting a new scope.

[cliff_hootarski]

Re: Samsung Plasma PN50a510p3f

As an aside, I've noticed the bottom right heatsink is now getting hot, top right is getting a little warm vs room temp on the rest.

And the TV just shut itself off!