Samsung 50" Plasma HPT5044 No Picture

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Yep, try that... it's quite possible the rest of the screen will either just light up dimly or show random noise.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Well just hooked it up. Turned it on and nothing. Not even a slight flicker on the screen.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Hmm. I cannot be sure then, but there might be more problems on the Y-sus.

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

I did the same- Mosfet right below the AA1 burned (b20nk50z) is that common?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

How did you check it? Is it the mosfet under the bottom left heatsink?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Wait isn't that a voltage regulator?
The one on mine doesn't seem to look burned, but the bottom of the board where its solder kind of look odd.

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

LOL There is a HOLE in the top of it. Plus it sparked a little. Yes, it is below (not attached) the bottom left heatsink on the board. I unplugged the upper ybuffer, left the low one plugged in and it stayed on with no further exciting moments. It was buzzing pretty well beforehand so I wonder if it was about to go and took the upper Ybuffer IC with it? Or vice versa? I ordered an upper buffer and will send in my Ysus to get repaired- I just want to make sure That's all that is needed so I don't blow any of my new parts!

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Not a regulator, but same case package as one.

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

Yep, same same. The bottom of my board also looked like it had some heat issues, and the Ysus was buzzing- then when I removed the IC from the ybuffer and plugged it all back in it smelled and the went sparky sparky at this component.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Wait, so with the lower buffer board and the ysus only plugged in, the TV was able to turn on? What was your initial problem when all three boards were plugged in? Was there any thing on the screen at all when you hit the power button?

I hear a small buzzing on the ysus with or without the buffers connected. It was only a little buzzing so I thought it was normal. I can hear feint buzzing coming from the x board as well.

So you plugged in the upper buffer with the IC removed with the Ysus and that component blew? I wonder why nothing happened with mine. (Or maybe mine was already blown?)


So what does that component that burned do?

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

No picture ever- just sound. I don't know what that component does- tom?

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Were you able to get anything on the screen with only the Lower buffer and Ysus plugged in?

[dsnyder586]

Re: Samsung 50" Plasma HPT5044 No Picture

No, no picture at all It starts up, makes the startup sound and chagnes channels/I can hear the channel just no picture. The guy I bought it from described that he was watching and the screen went from picture to black from one side to the other.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Alright so I decided to test the other mosfets and I think I found a shorted one. 88N30W 723638, it was located under the bottom left heatsink.

Pins:
1-2: 17 ohms
1-3: 17 ohms
2-3: 1.0 ohms

I looked up the SMD component (b20nk50z) Its a 17A 500V MOSFET. I found some on ebay.

Trying to find a way to desolder it and test if its shorted or not.

Until then I'm gonna test all the mosfets under the right heatsink.

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

Those readings look bad to me. It has a drain-source short (1 ohm is likely dead zero but you meter has lead resistance) and gate-source / gate-drain leakages.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

How do you find a replacement for this MOSFET? I found some on eBay "88N30W" but the bottom label is different. Do the bottom numbers mean anything?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

All that's important is 88N30W.

The bottom numbers are a date code/manufacturing lot code etc.
723 would possibly imply week 23 of 2007.

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Ahh I see.
Found this one on ebay I'm probably getting.
http://www.ebay.com/itm/2pcs-88N30W-...item19d5f78ebe

I checked all the other mosfets and they seem okay. (havent checked the smd fet yet, can't find a way to measure it out of circuit but it seems okay hopefully)

I'll probably order and replace the mosfet. And hook the ysus with only the upper buffer again and hopefully some picture shows. Then i'll just send the buffer boards to be repaired.

If the Ysus is good, can a damaged buffer blow the ysus again?

[tom66]

Re: Samsung 50" Plasma HPT5044 No Picture

On a Samsung, I think the Y-sus can be damaged by a shorted buffer...

[tieny]

Re: Samsung 50" Plasma HPT5044 No Picture

Yeah I thought so

I'm thinking I should buy the mosfet first, replace it, test out the y buffers, and if something goes wrong with the ysus at least I can still send the buffers in to be repaired or not if I decide not to.

Or I could buy the mosfet and send in the buffers at the same time and get everything at the same time. Then test everything at once but if something goes wrong I'll probably be left with bad buffers and a bad ysus. So I'll probably just move on from this project if that happens with this option lol.

option 1: The buffers could still prevent the TV from going on because its still damaged. (but if buffers don't damage the ysus and the picture goes on then success! ysus is repaired) total loss will proably be around 10$ if something goes wrong

option 2: Everything could be assumed repaired and probably has a higher chance of success (if ysus is assumed fully repaired) but if not total loss will probably be around 80$

Ah decisions!