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Samsung PS50B5302SW dead

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watteau:
Hi,
Sounds like a standby supply fault.
Circuit attached if you need it.
Regards,
John

ProDave:
Thanks

I had already got the circuit bit it never hurts to post if for others.

This is an odd one that has me foxed.

Initially the 5V standby was all but dead.  After replacing all the electrolytics in the standby circuit the 5V standby is "working" and I have the standby light, but try and turn the set on and thr 5V standby sags and it fails to start up.

I presently have it working on test with a separate little power supply providing the 5V standby.

It's not a capacitor fault as they have all been replaced. It can't be a semiconductor fault, surely if it was the 5V standby would not work at all.

So what else can make the 5V standby "work" but not be capable of sourcing enough current to turn the set on?

downunder:

Looks very similar to a Panasonic standby circuit I was working on last week. Turned out to be the opto PCM801S, but the reference IC CM401 could conceivably cause it too.         Bruce

Liam:
I'm having issues with my Samsung psu, take a look at my pcm801s opto
Do you think that this is worth replacing?

downunder:

The opto doesn't look too healthy, Liam. Is that just dust on the pcb beside it or has an electro leaked?

That would certainly affect the operation OF IC801S which looks to be the control IC for generation of Vs.

Bruce

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