My Samsung 50" Plasma just died. After reading various forum posts, I learned a likely culprit may be Electrolytic power supply caps. I removed the back cover and located the main power board. It is roughly 1 foot square and appears to have a front end isolation switcher and individual voltage outputs connectorized and cabled to the other 4 boards. At the AC input I found 2 ( one per L1/L2) slow blow miniature ceramic 12A fuses, one of which was blown.
I replaced the fuse, hoping, and sure enough it immediately blew on power plug in. I see no capacitors that appear bloated in any way. I see no obvious damage. I used an ohm meter to just check all caps for shorts. None found as I saw each cap slowly charge even with my low voltage meter. That doesn't mean they don't break down under voltage but I found nothing shorted. I did the same for each switching transistor and also found no clear shorts.
Because of the history of failed caps and I have all ShaWha large HK and smaller WL type caps. I'm thinking of replacing them all but wanted to ask if anyone has Plasma TV troubleshooting experience?
Is it safe to power the supply board with all the other board connectors ( the loads) removed to see if the fuse blows without any load on the supply? I'm worried about logic or other interlock signals that might be important.
Does anyone have a common sense approach divide and conquer strategy and or a schematic for this Samsung power supply board?
I went ahead and disconnected all the secondary boards from the power supply and replaced the fuse and powered it on. The fuse did not blow. I then connected the processor board and audio/video input processing board and powered t up again. No blown fuse and know the remote control appeared to work and various LEDs looked normal.
I then checked the high DC voltage to what appeared the Plasma display control boards. The voltage appeared ok at 200V to both boars which was consistent with a Samsung label for NTSC.
Then I just went for it and connected the Plasma boards and turned it on. Wala, it worked. That is spooky. I did vacuum inside and reseated the power board and generally made sure everything was ok and connectors seated.
I have now run it over night and it has operated normally. I have an electrical design background albeit very rusty. I had recalled that some Electrolytic capacitors when underrated and or over heated can punch through the dielectric and then self heal once the cap cools off and the voltage removed. Does anyone have thoughts about this and whether replacing the power supply output filter caps would be wise if it happens again? Or throw in the towel.
Given the dropping prices and cost to repair plus shipping plus its an intermittent problem, it hardly seems worth not just buying a new one if the problem continues. The 50" Samsung Plasma TV is 24 months old. A tough call.
Any thoughts appreciated.