Philips 50FP5532D plasma Ysus fault

[alanos313]

Hi all,

I have recently been trying to save a Philips 50inch plasma TV with a faulty Ysus and lower buffer board. I have found and replaced two faulty MOSFET transistors on the Ysus board, and bought a replacement (second-hand) buffer.
On fitting the parts and powering up, the TV worked perfectly. For about 3 hours. Then the picture went fuzzy, with some ghosting and sparkling, interspersed with very bright flickering of the picture.
I turned the TV off and allowed it to cool for about 30 mins. When I turned it on, it was OK again until it warmed up, when the same problem returned.
I checked the voltages on the power board (VS and VA) and made sure they were correct. The TV continued to show the fault for around an hour. Then suddenly the picture returned to perfect clarity. It stayed perfect for around an hour, then with an audible 'pop' the picture disappeared completely. Sound continued. I switched off and left overnight.
Upon inspection, i found a blown IC on the lower Y buffer. I removed the buffer, and swapped over the blown IC with a good one from the old buffer. I also checked the Ysus board, and was surprised to find all the MOSFETs to be ok. So i fitted the repaired buffer, and switched on. Again the picture was perfect for a couple of hours. Then the same fault occurred, although as of yet it has not blown the IC. I have now switched off, and decided to ask on here what I should do next? My inclination is to fit a complete Ysus repair kit even though the components all seem ok when tested with my multimeter. I cannot see any signs of bulging on any of the caps on the Ysus board.
My question is, What could be causing the fault to occur when the boards get hot? Is there a particular component I should be looking to replace? Has anyone else had this same fault before?

The Ysus part number is LJ41-05120A.
The buffers are LJ41-05121A (UPPER) and LJ41-05122A (LOWER)

Thanks in advance for your thoughts

:-)

[ben7]

Re: Philips 50FP5532D plasma Ysus fault

Double checked that all connectors are put in place nicely?

[alanos313]

Re: Philips 50FP5532D plasma Ysus fault

Double checked that all connectors are put in place nicely?

Yes, checked and re-checked. Ordered a Ysus repair kit from eBay for £25. I am thinking maybe one of the FETs is screwing up when hot. The kit also has a few caps and resistors etc in it, i hope once i change them all it will work properly! Just an odd fault, most times things improve as the set warms up... mine seems to be the opposite! I have found a few slightly bulged caps on the power board, however the voltages seem ok even when the TV is hot...

[cadiman]

Re: Philips 50FP5532D plasma Ysus fault

Used buffer or buffer ics are a really bad idea here.

The problem is you had a good y board and ruined it with used faulty buffers.

You do not want to put used buffers in any tv mostly if they didn`t come out of one of your tvs.

If you buy used buffers and they don`t work you can send them back. The problem is are they going to repair your y board for you that their bad buffer board ruined?

The easy answer is, no.

Also, rebuilt buffers are a bad idea too since these companies only replace the faulty buffer and not all of them on each board.

You need to find companies that will replace all buffer ics on both boards to have the proper repair then mate them with a for sure known good y board. That is why these are mostly sold in a set of three with a warranty too.

The mosfets are most of the problem but there are other components that can fail.

The kit you are buying should give you all the items needed to repair a y board that failed due to a shorted buffer.

[alanos313]

Re: Philips 50FP5532D plasma Ysus fault

Ok so here is an update...

I have now fitted the Ysus repair kit. Also have a new lower buffer. When I switch the TV on, the screen is black. If i remove the lower buffer and power on, the top half is displayed, albeit with some sparkles. With the lower buffer connected, there is no picture! Both buffers are clearly ok, so can anyone tell me which component on the Ysus board is likely to be causing this symptom? Or could it be a case of adjusting the pots on the Ysus board? I have already checked voltages from the power board and they are spot on!