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Samsung PS50B5302SW dead

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ProDave:
Samsung plasma tv totally dead.

No standby light (not even sure there is one on this set)

If you put your ear right next to the PSU board you can just hear the very faintest chirp chirp like it's trying to fire up and immediately shutting down.

I take it therefore a replacement psu board will fix it.  Is it likely anything else will have died or just the psu?

downunder:
Hi ProDave,

That's a huge gamble, assuming it's the power supply. Have you done any other checks. e.g, does it fire up if the scan boards are disconnected from the power supply, is the LED on the control board flashing, is PS-ON pin changing level when you power it on, is standby 5V present all the time the set is connected to the mains? As far as I recall, all Samsungs have a standby light.

ProDave:
No outputs at all, even with power boards unplugged from PSU.

The only output showing any hint of an output is "PS_ON" hovering between 1.2 and 2.2 volts.

Anyone got a schematic for these power supplies, or even a full service manual for the set?

the power supply board is BN44-00274B revision 1.2

ProDave:
If I unplug the ribbon cable to the small signal board from the PSU, I get 2.6V on PS_ON and 5.0V on 5V stby

Dead SSB pulling the standby power down?

Another quick test.

SSB unplugged, 1K resistor between 5v stby and ground, pulls 5V stby to less than 1V

So 5V stby won't even source 5mA

So PSU fault or SSB fault?

ProDave:
Okay some real progress.

Power up 5V stby from bench psu. now for the first time I have the standby light on the front light up.

Try to turn the set on, and after a few false starts (relay clicking) the set powers up and picture is fine.

So it looks like a PSU fault, and clicking relays usually means dud capacitors doesn't it?

Is there a service kit to fix this PSU rather than replacing it?  Can't find one on Ohm supplies.

P.S I have the service manual now for the PSU from Electro Tanya.

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