50" samsung plasma ysus problems

[gaza007]

Hi All, yet again i'm back asking for some of your wisdom

I've 2 PS-50Q97HD tv's 1 for spares and the other to repair

The tv i'm repairing only had sound no pictures so I initially thought it was the y board, upon checking the board I noticed the fuse had popped on the y board itself, so I replaced the fuse and switched the tv back on.. now the tv does the usual Samsung clicking noise from the logic board not wanting to fire it up so I removed the fuse and the tv started up again but no picture obviously.

I then removed the y board and the up & lower boards from the spares tv and fitted them to this one.. The tv fired up ok but then there was the noise of escaping gas and then the inevitable bang and the insulator which is known for going on these boards popped..

My question is this.. The y board that was originally on the tv seems to have a little charring round where this insulator sits and aside from the popped fuse there is no evidence to think the board is faulty but is it?? I thought it may have just been the usual repair for the clicking when I put the new fuse back in but after putting the new board in it fired up ok so not the power board...

I've included the pictures of the original y board and the up and lower boards I've also included a picture of the insulator and the underside of it too.

Any help is appreciated.



The insulator in question is just under the AA1 sign

https://www.badcaps.net/forum/pictur...&pictureid=231

https://www.badcaps.net/forum/pictur...&pictureid=229

[tom66]

Re: 50" samsung plasma ysus problems

You fitted the Y board and buffers from the broken TV into the TV you want to fix, and they went pop too? Can you check if the Vs voltage is good from the power supply - use a meter to check the voltage at both ends of the fuse relative to the metal chassis of the TV while it's on... you're expecting around 190-200V for a Sammy.

[gaza007]

Re: 50" samsung plasma ysus problems

Hi Tom, yeah the working board popped when I put it into the tv I'm repairing. I'll check the volts when I get in later

[tw2005]

Re: 50" samsung plasma ysus problems

These are notorious for shorted Upper buffer and blown 88N30W FETs due to the shorted upper buffer. I don't have a board to compare too anymore but I suspect that spot of discolouration is the location of those FETs. What was the fault of the donor TV you took those parts from. Sound & no picture?

[gaza007]

Re: 50" samsung plasma ysus problems

Hi Sorry for the late reply I was away for a few days.

To answer Tom's questions, the Volts going to the fuse nearest to the power in connection registers at 240v either side even when the control board is clicking on and off 'normal', the fuse mounted roughly in the middle of the power board is measuring 122v at one end and 124v at the other, of course they go down to 0v when the control board clicks off. This doesn't sound like the right amount of Volts to me Tom, if this is the case I have a power supply I could use for spares if you can suggest whats wrong with it??

Thanks for the reply tw2005, When I got the tv it had only sound no picture, upon opening the tv I checked the YSUS internal fuse which had popped, I replaced it and the tv started doing the usual Samsung clicking trying to fire on and then switching off. I replaced the board with a known working YSUS and that blew the FET chip staright away ''and you could tell it was clearly blown''.
I have just replaced the XSUS board as was told this could be the problem but that didn't change a single thing.

[tw2005]

Re: 50" samsung plasma ysus problems

Hi Sorry for the late reply I was away for a few days.

To answer Tom's questions, the Volts going to the fuse nearest to the power in connection registers at 240v either side even when the control board is clicking on and off 'normal', the fuse mounted roughly in the middle of the power board is measuring 122v at one end and 124v at the other, of course they go down to 0v when the control board clicks off. This doesn't sound like the right amount of Volts to me Tom, if this is the case I have a power supply I could use for spares if you can suggest whats wrong with it??

Thanks for the reply tw2005, When I got the tv it had only sound no picture, upon opening the tv I checked the YSUS internal fuse which had popped, I replaced it and the tv started doing the usual Samsung clicking trying to fire on and then switching off. I replaced the board with a known working YSUS and that blew the FET chip staright away ''and you could tell it was clearly blown''.
I have just replaced the XSUS board as was told this could be the problem but that didn't change a single thing.

When you say blew the FET chip are we talking buffer IC? Was it on the top buffer board by any chance? Also the control board can turn the TV off if it sees an issue. It did on one of the TVs with this setup.

[gaza007]

Re: 50" samsung plasma ysus problems

No it was the main chip on the YSUS board itself, the upper buffer chip 2nd from the the top looks damaged also. However the board which I orginally took out looks to have no damage whatsoever

[tw2005]

Re: 50" samsung plasma ysus problems

No it was the main chip on the YSUS board itself, the upper buffer chip 2nd from the the top looks damaged also. However the board which I orginally took out looks to have no damage whatsoever

Can you be more specific about the main chip on the ysus? What I'm trying to point out is I believe you have found the fault. If the replacement ysus was initially good but you connected it to the riginal buffers and the ysus blew then the buffers are shorted. That's the deal with these in a lot of cases.

If it's those 88N30W fets then you may be lucky enough to salvage one good board if there's enough good FETs left (if any).

Out of the 3 i fixed I had 1 ysus with 1 blown FET. The next had 3 and the last all 4 were gone if I remember correctly there's 4 88N30W fets.

So a good buffer set and ysus should get this going.

Also all 3 had blown upper and shorted 88N30w. All 3 had no visible signs of blown FETs or Buffer ICs and on mine no fuses blown.
Have you measured the VSUS at the ysus when you power on? You may for a moment see it just before it switches off.

[sgreen2004]

Re: 50" samsung plasma ysus problems

You fitted the Y board and buffers from the broken TV into the TV you want to fix, and they went pop too? Can you check if the Vs voltage is good from the power supply - use a meter to check the voltage at both ends of the fuse relative to the metal chassis of the TV while it's on... you're expecting around 190-200V for a Sammy.

Hi TOM66 i don't know if i'm posting in the white section but i have the tv in question samsung ps50q97hd and i am facing some very annoying problems, i had the very common sound but no picture so i opened the tv and found that the power coming from the psu was all normal so changed it anyway as have lots of spares and nothing so came to the decision that the ymain and buffers are to blaim so checked the IC chips on the upper buffer and one had a (c) like symbol burned into it so i checked the rest and they all looked ok but i'm unsure how to test them :/ i changed the blown IC chip (with great trouble) and replaced all 5 fets on the small heatsink for the upper board along with 2 resistors, 2 capacitors and a zenor diode, also another small fet, i now have a picture! but hers where it gets interesting its very snowy with very thin black lines however i can access the menu, if i run the tv on the bottom buffer the bottom of the screen glows purple (dark) and if i connect the top buffer and bottom as i said it works but the psu gets very very HOT and makes a loud buzzing noise although appears to be partly working. any idea's please would be greatly appriciated! steve

[tom66]

Re: 50" samsung plasma ysus problems

Probably best to start your own thread, but any chance of a picture of the fault?