Samsung PS50Q91HD Y-SUS and related

[nickon51]

I am repairing the above model, a 50" Samsung Plasma TV. The symptoms were as you would expect, no picture and chassis goes back to standby shortly after switch-on. I purchased a Y-SUS repair kit and repaired the Y-SUS board. Following advice from a few forums I left out the top Y buffer board and switched on. All seems ok with faint snow on the bottom half of the screen. Checking the upper buffer board revealed 2 faulty 3407F IC's. I removed these, re-fitted the board and could see a picture in the top 1/4 of the screen, then faint snow for the bottom 3/4.

I'm wondering why there is only a picture on the top 1/4 of the screen. The second 1/4 is driven by the IC's that were removed and the last half is driven from the bottom buffer board.

This may well be of academic interest only, but does the logic board need to know that the previous buffer scan was completed sucessfully before enabling video on the next buffer scan? Should I worry that there is only the top 1/4 of the picture. I was expecting to see a picture with only the second 1/4 missing.

I'd be interested in your comments.

[tom66]

Re: Samsung PS50Q91HD Y-SUS and related

Depending on the architecture, the buffers MAY be chained, so that after they receive their scan pulses (64, 96, or 128 per IC), they trigger the next scan for the other buffer. The only purpose of the buffers is to provide the scan pulses to the plasma panel so data can be loaded onto it before it is sustained.

[tw2005]

Re: Samsung PS50Q91HD Y-SUS and related

I am repairing the above model, a 50" Samsung Plasma TV. The symptoms were as you would expect, no picture and chassis goes back to standby shortly after switch-on. I purchased a Y-SUS repair kit and repaired the Y-SUS board. Following advice from a few forums I left out the top Y buffer board and switched on. All seems ok with faint snow on the bottom half of the screen. Checking the upper buffer board revealed 2 faulty 3407F IC's. I removed these, re-fitted the board and could see a picture in the top 1/4 of the screen, then faint snow for the bottom 3/4.

I'm wondering why there is only a picture on the top 1/4 of the screen. The second 1/4 is driven by the IC's that were removed and the last half is driven from the bottom buffer board.

This may well be of academic interest only, but does the logic board need to know that the previous buffer scan was completed sucessfully before enabling video on the next buffer scan? Should I worry that there is only the top 1/4 of the picture. I was expecting to see a picture with only the second 1/4 missing.

I'd be interested in your comments.

What was the kit worth?

I've fixed 3 of these all had dead upper buffer and blown ysus. On all 3 only the 88N30W FETs were shorted. About $7.50 a pair delivered online.

Did you test any of the parts replaced to see how many were dead?

Just curious. Also I believe you can use a couple different buffer boards in this set. I did with no dramas.

[nickon51]

Re: Samsung PS50Q91HD Y-SUS and related

G'Day

The kit:

http://www.ebay.com.au/itm/271002634...84.m1497.l2649

cost me AUD48.05 inc delivery to Oz.
Yes I did check the bits after I removed them and found that only 1 88N30W was shorted. The other components measured ok.

The sheet that comes with the kits says that you will need a new upper buffer board as well. That alerted me to check carefully the upper buffer board which is when I found two faulty ic's there.

The cost for parts should end up being about $80.00. I will check more carefully next time to see whether all 88N30's are u/s.

I have only seen reference to one type of buffer board.

Thanks for your comments, its nice to know that I maybe could save some $$$ next time.

I've have some 3407's on the way. I'll keep you and Tom posted.

Cheers

[tom66]

Re: Samsung PS50Q91HD Y-SUS and related

Ugh. Jackcon caps. You'll be better off with the original crappy Samwha! Throw the Jackcons out when you get the kit and replace them with something decent.