Samsung PS50C91HD - No picture, not sure which board is faulty

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Nope I have been meaning to go shopping for one.

[tom66]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

You can spend $50 (USD) and get a decent analog scope these days, on the used market.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

yeah I will have to grab one.

I wonder what else needs replacing. would caps cause this?

I haven't yet got the 3 caps tw2005 suggested.

[tom66]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

I've had caps trigger protect fault on the 42" panel, so I suppose it's not impossible... in that case though the cap was bloated completely.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

if them fets blew again nothing would come up on the screen right?

[tom66]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Yes and no, certain shorts could trigger protection after the panel initialises...

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

I can always get this flash when turned on.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

disconnecting the upper buffer board I get half the screen flash then it goes into protection mode.

Can this tv run with out upper buffer board, if not could this possible be my buffer repair?

Removing the chip would I'd expect the tv to turn on with chip removed?

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

nevermind I have found the answer to that.

you can run it. Would it be possible the voltages aren't being regulated properly and the y-sus is going into protection mode.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

just tested the old mosfets from the top they tested good so I have a few spares.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Testing new 2SK2837 N channel fresh from packet.
a) black on pin 1- red on pin 2 - O.L
b) black on pin 1- red on pin 3 - O.L
c) black on pin 2- red on pin 3 - 2,732 kohms

One of the old ones from the bottom heat sink.
a) black on pin 1- red on pin 2 - O.L
b) black on pin 1- red on pin 3 - O.L
c) black on pin 2- red on pin 3 - 0.741 mohms


just testing them to verify that they are working correctly.
Plus still trying to get my head around this testing mosfets.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Q5500 - k2837 - bad
Q5304 - 88n30w - bad
Q5303 - 88n30w - bad
Q5302 - 88n30w - bad
Q5306 - 88n30w - stuck on

I hope I tested right.
red probe on drain and black probe on source in beep mode on diode test on my digital multimeter.
after touching the gate with red while keeping black on the source, then touching back to drain with red probe.

Just learned something. only one was bad that was 88n30w location Q5306.
Needing some resistors that come in the kits and the zenor diode.

[tw2005]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

I have no suggestions because all I've ever been faced with are the 88n30w fets and an upper buffer. At this time I'm not over interested in the dead samsung I have which needs a lot of work except I am interested in how the repaired buffer you did turns out.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Yeah me too I wanna see if I done a good job or not on it. I have no ESR meter to test the caps but I will chuck some new ones in.
if that don't work, I will replace the resistors and zenor diode. then if that don't work I will order a new Y-Sus.

The breif flash I am getting seems like the set sensors there is no control of the voltages and probably shuts off to the y-sus to protect the pannel.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

fired it up with some new 25v caps replacing them 3.

with out buffer boards protection light was off not sure if this was fluke on a cold start or what.

installed buffer boards protection light on still. removed buffer boards protection light on still.

Cold solder?

I could hear power running threw it with out the buffer installed.

[Amraks]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

I think I am up for testing them mosfets again as I think the buffer chip blew them again.

I have some new buffer chips coming as the ones i ordered were not in there correct packaging.

they were taped to a bit of foam and I done my best to work with them but the chip did not line up correctly.

[Andreasbest]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

Hello all.
i have the same problem like many others in here, i have a ps-50c91h and i get sound but no picture / backlight at all.
Facts : The Vs and Va voltages on the PSU sockets are ok (206 for Vs and 63 for Va), the LED5800 on the Y-Board doesn't light, not sure if it must be ON but it's not.
Question : Service manual troubleshooting advises replacement of Y Board in this case (blank screen). Should i get this as a fact and check only the Y board for defect component(s) or not?

[spippolone]

Re: Samsung PS50C91HD - No picture, not sure which board is faulty

I take the opportunity to follow up on the first part of this question The problem it similar for my TV.
I have a Philips 50PFP5532D. Sometimes the TV goin on and it work fine, someone you can see with horizontal line, someone it don't start, but if you go in off and on again start fine.

I found some caps fault on power board, and une on X-main Board and I replace it.
After the replace, the TV never goin on.
The power supply it's OK all voltage there are.
When I turn on the TV you can see the back led this video https://youtu.be/zDLEUFdOK7E. When the led on the board blinking you can a little buzz from X-Main and Y-Main, all the panel goin on 1 second, the VS go to 215V for a second and after VS go down and the panel switch off. The screen in this video https://youtu.be/QY_vWkm3YBg

The front led is OFF when the TV is in Stand-by and fixed RED when the TV is ON

X-Main is 50HD W2 PLUS X-MAIN
Y-Main is 50HD W2 PLUS Y-MAIN