Hitachi P50v701 ps quality

[freakaftr8]

Hey all I just picked up this hitachi p50v701 plasma. Known issue is turns on quick flash of the raster then shutdown with blue led flashing 3 times. Closer inspection shows 2 100v 3300uf caps domed in the vs output of the ps. Ok so research shows that this issue will eventually spike the upper and lower scan boards shorting an ic and wreak havoc on the ysus. I got lucky on this set cause the buffers are still testing ok. With both buffers disconnected set will stay on for about 2 minutes then shutdown with same 3 blink. My testing shows massive ripple in the vs line. You can actually see this on the screen with massive maldischarge pixel flash and vertical smearing of the osd before it cuts out.

I have not run into another power supply using such high value caps like this. With the rest of the tv seeming like high quality boards and build why would they cheap out on the power supply and cut corners and not have more circuitry added in so they don't need 3300uf caps?

[tom66]

Re: Hitachi P50v701 ps quality

My guess is the caps were insufficient - potentially they just reached the end of their useful life.

[freakaftr8]

Re: Hitachi P50v701 ps quality

True. I've repaired many power supplies on the past but this supply seems rudimentary.

[freakaftr8]

Re: Hitachi P50v701 ps quality

Ok new caps in the power supply. Same problem. Power up and quick flash of maldischarge. Then powers off immediately and 3 flashes. Ysus board error.
My question. I have had repaired buffer boards before but how do u test these buffer boards? I cannot visually see any burned ic's. and both upper and lower board when installed individually does the same thing. Although for like 5 seconds before when the lower board was on the set stayed on with a lit lower raster. Blank of course.
Thanks guys

[freakaftr8]

Re: Hitachi P50v701 ps quality

Actually it was the buffer boards. I'm in the process of rebuilding them at the moment. Got the top one finished. Loos good just one chip bad there. The bottom on the other hand has four shorted chips. Fun fun. Still trying to work the bugs out of it.

[Shane711]

Re: Hitachi P50v701 ps quality

How do you test the buffer boards without seeing a burnt IC? I tested for short to ground but I did not find any shorts. I am thinking I have a bad Y-SUS or PS.