plasma tv PSU

Just to add to this..

The tv works fine all PSU voltages within specs.. Then it starts clicking a bit and then shuts down. Seems to click when the brightness changes on the TV. (Dark picture to bright picture) and it seems to fail more on bright pictures like cartoons.

When it shuts down it wont restart until the power is removed completely. The standby light will change from red to green, but to no avail. The 300V doesn't come up in the PSU. No Vcc only STB voltage. Unplug it plug it back in and comes right up.

Poking around with freeze spray on some of the suspect components recomended by the service manual it will shut down, but not instantly as expected. It takes a minute or two...

Im puzzled what the clicking soud inside this thing is. It is not the relays and the intensity changes. It always clicks a few times while warming up.

a e V

ck

ded

. It

ing

Replace the bad 'lytics and check again. Got an ESR meter? If not, it's time. Even the cheapy $50 MAT Electronics meter will do OK. SMPSs are particularly fussy about the caps. 'OK' rarely is OK. Secondary outputs have to be very good. Panasonic FM, Nichicon PW, HM, HN an HZ series caps are good. For SMT caps Panasonic FK and FP are good.

G=B2

G=B2

Replace the bad 'lytics and check again. Got an ESR meter? If not, it's time. Even the cheapy $50 MAT Electronics meter will do OK. SMPSs are particularly fussy about the caps. 'OK' rarely is OK. Secondary outputs have to be very good. Panasonic FM, Nichicon PW, HM, HN an HZ series caps are good. For SMT caps Panasonic FK and FP are good.

G²

I have a bob parker mk2 meter that I buit a few years back. I poked around with it and didnt find any bad caps, although I didnt remove them all from circuit. I have my suspiscions that it is bad caps though. There is a serivce buletion that says to check the 2 400V 250uF caps. They checked ok out of circuit.. I guess I will double check all the caps again.

If it's a Samsung 4264 or similar, look for bad solder at a couple of the switcher transistors near the middle of the PSU. The eyelets were too small and need to be scraped back and soldered.

Mark Z.

Shotgun the caps in the PSU if you want to go to the time and expense. Do the ones in close proximity to hot items like heat sinks, diodes, >1watt resistors first. Placement of caps in those locations will always give trouble eventually and have much shorter lives. Wish I had the set, this is just the kind of troubleshooting challenge I love.

--
Live Fast, Die Young and Leave a Pretty Corpse

Actually I enjoy it too, although this is my first switcher to fix.. I just wish I had someone around to learn all the tricks from. If I didn't enjoy it, I would just watch the tv as is becuase it functions without issue most of the time or just buy a PSU thats been rebuilt for $70.. I enjoy fixing anything that gives me a little challenge. This is the first piece of equipment that I have ever cracked open which had a sufficinetly detailed service manual.

Thanks for the tips.

Its actually a Hitachi W32-5000 similar to a P5000 with a MPF4700 PSU

Thanks for the advice!

You're welcome. I've now repaired 5 >400 watt PC PSUs. Used to just toss them and buy new. A couple friends who saved the failed units gave me these for parts so I decided to have a go at repair. The last unit was a

650 watt PSU that failed after a year. Made a chirp with then AC was plugged in. Grounding the green PSU 'on' wire did nothing. Since I have no ESR meter I took a count of the caps and their values and drove to a local electronics supply store. I also gave the PSU a good visual, tested some obvious fuse-able type resistors and some discrete semiconductors. Also looked for bad solder and signs of hot components, discoloration, you name it...whatever my past experiences had taught me not only with switchers but any high power electronic device. Finding no obvious signs of damages I purchased some replacement caps found in areas I described above. Cost me about $20 US. Took me less than an hour to replace and reassemble. I ended up with a spare 650 watt PSU. My new quad core AMD based PC with a 120 watt CPU needs a minimum 600 watt supply. My NVidia graphics card has a separate 12 volt plug since the PCIe bus cannot deliver enough current. Also have 3 SATA hard drives and two DVD burners. Lots of power hungry devices I don't want to tax a smaller PSU on. Plus I overclock the quad PSU to 4 ghz and that requires a high degree of voltage regulation precision. So not any old PSU will deliver. I've had no problems since I bought the hardware back in July.

--
Live Fast, Die Young and Leave a Pretty Corpse

On that note.. I just found a blackened cap which is close to a 2w resistor which also appears to be black. New resistor and new cap time.

Replaced all the smaller caps around hot areas and it appears to be working ok, although this tv still is making a clicking sound when heating up and cooling down.. It really sounds like a relay, but It is something else.