Samsung 50" Plasma HPT5044 No Picture

[tieny]

I usually just fix LCDs and don't really like dealing with plasma tvs since I never have much luck with them (probably fixed 1 out of 5 :[ ). But this one was given to me for free so its worth a shot. Though with my luck I don't have much hope.

TV symptoms are, after the power button is pushed, the TV makes the ON sound however no picture appears on the screen (no light on TV at all, even in a dark room).

Checked the screen for any internal cracks but there isn't any. So I'm most likely concluding it has a bad Y-sustain and probably bad y-buffers as well? What do you guys think?

I checked two fuses on the YSus Board and both are good. No burn marks on the IC leads of the buffer board HOWEVER the uppermost IC looks like it blew and burned from the top of the chip with two white spots (see photos)

I don't know much about plasmas either. Having all those different boards in a plasma always seems to scare me sometimes lol.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

VERY common issue with this chassis.

It is the buffer board that needs replacing but also some transistors on the Y-main board.

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

I JUST bought the EXACT same tv- TODAY. lol. Burned IC at the top of the buffer (I actually saw it smolder) Tom- anything else I should look at as the CAUSE of the chip burning, or does it just happen with age? I already sourced a new buffer, just want to make sure I do not toast it too.

Thanks in advance!!

Dave

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

Just to show I am not kidding- too funny!

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Hmm, looks exactly the same haha. maybe theres some hope with this plasma afterall ;]. The thing that worries me is that I often read that both buffer boards AND the y-main board should be replaced at the same thing to make sure it is fully repaired without any risk of further damage.

(Had a very bad experience with another plasma with this bad y-main and buffer problem lol)

I'm wondering the same thing. Is it just a common problem with this chassis due to age? Or is there something that is causing this common problem within the y-main board? Tom- you mentioned some transistors that needed to be replaced on the Ysus, which ones?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Only the upper buffer needs replacing.
The Y-main can be repaired.

The top most heatsink closest to the buffer boards has the shorted FETs on it. Check each is not shorted, replace as necessary (will cost ~$20) run with lower buffer (should get garbage on the screen), buy new upper buffer, enjoy TV.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

There were 5 FETS on the top left heatsink. From left to right in that order.

What would be the best way of testing them?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

oops forgot the photo

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Just check every combination of pins, 1-2, 1-3, and 2-3 on diode test; only one way is necessary. If you see <100 on ANY reading then the fet is most likely bad.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Just checked each FET, all are reading on "1" out of range when on the diode test. Except for pins 2-3 itll read about 500 ohms for each.

Does that mean there all still good? If I were to remove the upper buffer board with the lower and ysus connected would the TV be able to turn on at least?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Hmm, they seem OK.

You should try with NO buffer connected. It may fry the new/OK buffer.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Just put the ysus back on the panel, but no difference without the buffer boards. Still nothing on the screen.

Left it on for a couple minutes, then I felt the heatsinks on the Ysus. The top left seems cold, the bottom left one is hot, and the rightmost one is cold.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

You don't expect an image without the Y-sus
Problem is you need a scope to be sure the Y-sus is OK.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I see, so theres no way of knowing if the ysus is okay. I could place the lower buffer board only to see if theres some picture but its a risk...

Ah such a gamble, another reason I don't like dealing with plasmas =(.

But when I had both buffer boards and the Ysus hooked up there was no picture anyway? If the lower buffer was good shouldnt it show something on screen? Unless the damaged upper buffer is preventing the lower.

Other problems I have so far, I can't seem to find just the upper buffer board for sale. Shopjimmy is out of stock for the set as well.

I found this post that repairs both buffers and the Ysus for only 145$ (better than buying all three for $200+ eh?)
http://www.ebay.com/itm/Repair-LJ41-...-/280909667446
Thinking thats my best option so far but then i don't know if theyre reliable.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

It's only Samsung that blow buffers when there's a problem with the sus board.

Never seen it with Panny, or LG... and in fact, on both of the Samsung plasmas I have done, it hasn't happened either, though both of them were shorted X-mains. And both parts were cheap - £12 and £18.

Plasmas are great to fix (and usually easy -- part goes BANG -- there's the obvious problem), but you NEED a scope unless you like board swapping. Even if it's just a 20 MHz single-channel cheapie analog one.

One thing you can try if you don't mind damaging your broken upper buffer, is to remove the blown IC, then power it up. If it works, then replace that IC or the upper buffer. Worst case is it blows the next lowest IC when it addresses that one .

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Hm I wouldn't mind getting a scope even just a cheap one. Not really a fan of board swapping (well except for the main board sometimes). Another tool to add to my collection! One can never have too many tools right =D. Do you have any recommendations to where I can get one?

I don't mind damaging the upper buffer much, hey its already damaged right? The hard part is just getting the IC off (and especially all that glue gunk). I have done it before using a heat gun but I don't like the fact those little smd capacitors are right next to it. I might just order some chip quik solder to do the job instead.

If the IC is removed should I test it with both buffer boards connected?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Pick a good scope up from ebay or craigslist; you need it to be 400V rated and get a 10X probe with it (switchable is OK.)

You should be able to get away with just the upper buffer board for a quick test.

Removing it is best done with hot air. Place foil around the board and cut a hole for the chip to remove, that way nothing else will be damaged. Also, make sure you cut off the epoxy around it.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

I don't know much about oscilloscopes so I'll probably do some research about them later.

I usually use aluminum foil around the IC and heat it with a heat gun.

What is "epoxy"?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

The ICs have glue around them, you must remove this before removing the IC (use a screwdriver or knife.)

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Okay great! I got it off without any problems . I might need to buy some wick later.

So with the IC off, I should connect only the Upper buffer with the ysus and see if anything comes on? (and probably watch for a blowing IC) =D