Samsung Plasma PN50C550G1F : no image, but sound is ok

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

It's a little four pin connector, 0.1" spacing, square in shape and should not be connected. Vetical. Pins marked 1, 2, 3, 4. There may be another connector but don't use that as it's probably the programming header.

Thanks Tom66 for the clarification... At first, I thought you were talking about that programming header connector. I have located the 2x2 diag connector as shown on the picture.

i'll install the jumper on it and also on the PS-ON pin of the connector and run the tests and report the results.

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Yep that's the one.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

All right,

I have disconnected the really thin flat data cable connecting the logic board to the A/V board (LVDS cable).

I have disconnected the ribon cable between the PSU and the A/V board, and added a pull down (80 Ohms) on the PS-ON pin.

I added a jumper on the diag connector of the logic board (pin 3 and 4).

As soon as I turn the power bar on which the TV is plugged in, the power supply turns ON (It clicks like when I press the power button when everything was connected).

The logic board still go in its protect mode (led flashes 5 sec ON, 2 seconds OFF).

Vs on the PSU testpoint starts at its nominal value 212V for about 1 second, then ramp down to 0.

Va on the PSU testpoint starts at its nominal value 55V for about 1 second, then ramp down to 0.

Vscan on the Y-main testpoint starts at its nominal value -190V for about 1 second, then ramp down to 0.

Ve on the X-main testpoint starts a 0.40V and ramp down to 0.36V.
(But label says value should be 83V)

Jay

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

The LVDS I have disconnected is the one shown in picture

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

BTW, I have seen a kit of boards (Y-main, Y-buffer, X-main) for about 40USD near my place on ebay.

If there's a good chance the probelmatic board is one of them, it might be worth to get them...

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Please remove the X-main board and check it for shorts. Check transistors on the heatsink for shorts.

$40 is a good price if the boards are ok

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Update on the voltage for Ve...

I was about to remove the XMain to check for shorts, and realized it was disconnected ...

Ve starts at at 89V and ramp down to 0.
(The label says 83V), so not sure that to say about this...

Other measurements remains the same.

Vs on the PSU testpoint starts at its nominal value 212V for about 1 second, then ramp down to 0.

Va on the PSU testpoint starts at its nominal value 55V for about 1 second, then ramp down to 0.

Vscan on the Y-main testpoint starts at its nominal value -190V for about 1 second, then ramp down to 0.


So should I check for shorts on Xmain anyways, or is there something else to look for?

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

No, no need right now to check X-main.

Do you have an oscilloscope spare?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

No, unfortunatly, I only have a good old multimeter ...

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Ok, it would be a good idea to check the Y- buffer board.
https://www.youtube.com/watch?v=51SZsfH60EY

Also, there are no cracks on the screen at all, right? Including really small ones. Any one can stop it working.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Ok, it would be a good idea to check the Y- buffer board.
https://www.youtube.com/watch?v=51SZsfH60EY

Also, there are no cracks on the screen at all, right? Including really small ones. Any one can stop it working.

Ok, I will check the video and test the y buffer.

Screen look pristine ... So I doubt this would be the cause.
It would be visible from the front of the tv right?
Like if the glass would be broken?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

I removed the y-buffer and tested for shorts like shown in the video...
There're many detected by my multimeter, so I guess this isn't a good sign.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

The screen/glass seems flawless : no sign of crack/hailine/dent anywhere

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

As long as there are no cracks (it can be a really tiny one, like just a few pixels, or on the very edge of the panel) you should be able to fix this TV by replacing the Y-buffer. Where were the shorts found, in various positions or just around a few connectors?

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

I can confirm that there no visible cracks on the screen...
The shorts were found on almost all connectors and at various locations.
Some had many shorts and other only a few.
I tried the 3rd and 4th pin from the left as shown in the video, but almost all pin had at least a short somewhere.

I'll give it a try with the y-buf/y-sustain replacement boards I talk about previously. They are sold by a small repair shop not too far from my place and are supposed to be garanteed to work (tested).

Probably worth the shot to try.

Thanks a lot for your support.

Jay

[tom66]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Test the new Y-buffer too. I'd swap both Y-buffer and Y-sustain at the same time just in case.

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Test the new Y-buffer too. I'd swap both Y-buffer and Y-sustain at the same time just in case.

Yep, this is what I had in mind...
Thanks Tom66 for all your advice!
It is appreciated.

Even if it doesn't work, at least I will have learned a few stuff on plasmas

[jose6326]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

superbigjay, if the new boards you order from ebay do not work out for you let me know

i have the same exact tv and i was never able to repair it

the only board i didn't replace on mine was the main board

https://www.badcaps.net/forum/showthread.php?t=28943


thanks

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

superbigjay, if the new boards you order from ebay do not work out for you let me know
i have the same exact tv and i was never able to repair it
the only board i didn't replace on mine was the main board

Will do... I just picked up my boards for 40$CAD. (roughly 32USD).

Will replace them tonight and post any success / failure.

I'll check your thread too when I got some spare time.

Jay

[superbigjay]

Re: Samsung Plasma PN50C550G1F : no image, but sound is ok

Well, I have installed the new Y-main (Y-sustain) and the new Y-buffer, and the screen is alive, but now I have some horizontal lines on the top portion of the screen (about 1/6 of the height).

Is that kind of problem typically related to one of the 6 connector of the Y buffer, or to the X-buffer?

If I install my old Y-sustain, do I risk damaging the "new" Y buffer?

Any recommendation?