Samsung HPT5054X powers on, but only shows a few lines of distorted video

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

So Far:

Fuse F5700 is blown
Cap C5709 is bulged. Don't have an ESR, so I'll just replace.

Traced the circuit from fuse F5700, looks like it powers Ys and Yg, whatever that is. Everything is testing good so far, and have not encountered any FET's. Does this make sense for the symptoms I'm seeing?

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Ys and Yg are the FETs for the SOURCE (Vs) and GROUND (0V) sustain drive output.

[tw2005]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Spiking I mean as in you get residual charge left in the caps on the PSU. There's a 3 pin lead on the bottom rhs that feeds the E/F buffers, I think 90V from memory, i powered up one of these once and forgot to connect it, turned it off and tried connecting it straight away. It arced as i did and blew the chip on one of the ribbons that attaches to the panel. not repairable, I had just finished rebuilding the ymain and replacing the top buffer board, TV was fixed but now i had stuffed the panel.

just sharing my experiences so other people don't make the same mistake.

pretty sure Tom has a video for testing these exact buffers in one of the stickys, troubleshooting hints.
you don't want shorts in the input side nor do you want to see short between gnd and any of the connections on the panel connector ribbon side either on the buffer.

https://www.youtube.com/watch?v=25HT...tCVe9&index=11

https://www.youtube.com/watch?v=51SZ...tCVe9&index=10


The TV he fault finds has pretty much the same ymain, buffers etc. It's a really interesting video regardless to watch.

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

60V for the addressing on these panels. Yep, if you attach the 60V while the buffers are cold (5V off, enables disabled) they will fry... kinda why I'm worried about jumping the AC det on my 42" Panny, I don't know if I'll fry the panel if it de-sequences incorrectly...

[fuxxy]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

SOLVED.

Cap C5709 (680 uF, 25V) had a bulged top, and was shorted, resulting in fuse F5700 (1A, fast) blown.

Removed cap and circuit was no longer shorted to ground. Replaced cap & fuse, unit powered on with no other issues.

Thanks guys!

[tom66]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

Nice one. Haven't heard of many low voltage caps failing short but that's crappy Samwha for you...

[nwcs]

Re: Samsung HPT5054X powers on, but only shows a few lines of distorted video

I have a strange problem with the same tv. Customer tried to fix it himself and he said his original problem was no picture so he changed the y main and the upper buffer board. Now when turned on the left half of the picture comes on but is garbage and then the right comes on a few seconds later. If I press the menu button or input button the right half of the picture will change to more or less of a scrambled picture.