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

[Amraks]

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

There is one part I am stuck on thats the removing rubber or silicon heat sinks from y-main on the bottom of the board.

So ur saying there might be a dry joint on a fet in that section?

[tw2005]

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

There is one part I am stuck on thats the removing rubber or silicon heat sinks from y-main on the bottom of the board.

So ur saying there might be a dry joint on a fet in that section?

No, PSu can have dry joint issues on the FETs.

The ymain I'd expect shorted fets

If it's the black pads, get a hair dryer and heat them up. try not to deform them peeling them off, makes it easier to get hem to sit on the baoad again after repair.just get them nice and warm and should be good.

[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.

[tw2005]

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

I usually just check for shorts, bad i guess you mean shorted? You might as well replace the lot if only 1 is not short.

So that's out cct those results?

checked that smd fet yet?

[Amraks]

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

Yeah thats all the fets removed out of circuit.
Lucky last, pain in the arse, smd fet to remove.
Q5501 - B20NK50Z - bad.

I made up a small little testing circuit they are defiantly not functioning right.

ZD5502 did u replace this Zenor diode

And there is a few kits out there with resistors added to the package.

Would like to know where these resistors are located.

[tw2005]

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

Yeah thats all the fets removed.
Lucky last, pain in the arse, fet to remove.
Q5501 - B20NK50Z - bad.

I made up a small little testing circuit they are defiantly not functioning right.

ZD5502 did u replace this Zenor diode

And there is a few kits out there with resistors added to the package.

Would like to know where these resistors are located.

Nice, that probably helps me. No this is the first one I've had with the extra damage, I think if the kit has that in it and the rest of it matches what we're talking about it'd be silly not to replace unless you can test it. I think for the few cents and time I'd replace it.

What resistors we talking about?

[Amraks]

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

Thats what I am trying to figure out I seen it posted on here. if we can determine that. should be easy to test and replace. with out having to lift to many off the board.
I think its close to the zenor I am talking about.

[Amraks]

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

check these locations z diode @ #5502, resistors @ 5508 & 5509, v regulator @ Q 5501 I had these fail on the same y sus, along with fet's mentioned on the two heat sinks common with this board when buffers are toasted

https://www.badcaps.net/forum/showthread.php?t=14972

Not sure what he means by other heat sink.

[tw2005]

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

Resistors often measure their value in cct unless in parallel, visually you can often spot burnt or smd resistors can have a pin hole from blowing.

I don't think I'd be pulling them all out to test unless the result was doubtful.

I think Tom may have a video in the stickys for this series. could be wrong but he may have had bad caps and burnt resistors on that ymain. Been too long to remember and these TVs are not a favourite of mine.

[tw2005]

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

https://www.badcaps.net/forum/showthread.php?t=14972

Not sure what he means by other heat sink.

Well there are 3 heatsinks, i think he means the other large heatsink.
I'd probe all those parts anyway to be sure they have not shorted , but with the 3 I did I never found anything bad there but never assume.

[tw2005]

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

that part number in the kit, BZV55C is only a partial number, it needs a suffix to know what voltage zener

[Amraks]

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

thanks I will remove the top heat sink and fets and test

[Amraks]

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

While I had my hot air station out, I decided to remove the faulty IC from the upper buffer board.

It went successful, this is my first attempt at removing them. come up nice and clean.
Used a bit of Aluminium Tape to protect surrounding parts.

Will move on to the other mosfets after school holidays, gets hectic around here during school holidays and makes it harder for me to work.

[tw2005]

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

While I had my hot air station out, I decided to remove the faulty IC from the upper buffer board.

It went successful, this is my first attempt at removing them. come up nice and clean.
Used a bit of Aluminium Tape to protect surrounding parts.

Will move on to the other mosfets after school holidays, gets hectic around here during school holidays and makes it harder for me to work.

Sounds promising and I'd love to see a picture of your craftwork.

maybe if you get the buffer fixed, i might need your help.

[Amraks]

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

To remove the glue from the chip I used a bread clip works wonders and doesn't scratch traces

[Amraks]

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

heres my craftsman ship

[tw2005]

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

heres my craftsman ship

looks pretty neat, can't wait to see if you pull it off

[Amraks]

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

cheers I am confident I fix it up

[Amraks]

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

Ok I am back again I think there is just more than the fets shorted.

Y-Sus is still in protection mode, I get a brief flash of black fuzz when the screen is switched on.

I am out of ideas..

[tom66]

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

Do you have an oscilloscope available?