Dead Samsung plasma - NOT (?) Power supply

[holybob]

Hi, I've got a dead PS43F4500AW 43" plasma. It was working fine, I switched put it in standby, 30 mins later I couldn't turn it back on again. From web research, I suspected the power supply. I couldn't see any obvious bad caps but I purchased a 'used and tested' replacement power supply board from Ebay. The TV still didn't power up. So I purchased a 'used and tested' replacement logic / main board from Ebay with exactly the same result.

With original power supply, when you plug it in the green LED on the back of the main board does a double flash and it does this twice. Every time it flashes there a 'ticking' which sounds like a relay on the power supply is unsuccessfully trying to fire.

With the replacement power supply, the double flash happens 5 times, again the clicking noise for every flash.

I've tried disconnecting all the ribbon cables etc and with only the power supply and main boards connected, the light sequence still remains the same.

Any ideas please? Does it sound like the replacement power supply I bought could be faulty?

Bob

[dick_barton]

Re: Dead Samsung plasma - NOT (?) Power supply

With the set powered off and power supply disconnected use you meter on ohms range and check all the power supply test points on the X & Y boards to see if you have a short circuit on any of the supply lines. Ve,Vs, Vsc, Va, +5V, +15V etc. whatever supply points are there.

[holybob]

Re: Dead Samsung plasma - NOT (?) Power supply

OK, so with a multimeter on the power supply, I can see that VS and VA fire up for a split second (to 2v and -0.15v respectively) - they fire up when the clicking noise is heard (so twice on one power supply, five times on the other). Afterwards, I can get voltage reads on the components on the left hand side of the board, but the right hand side is dead (the split is almost exactly down the middle, where the centre heatsink is - see image).

Following the helpful suggestion from dick_barton I unplugged from the mains (and disconnected the power supply board internally). I'm getting a little outside my electronics comfort zone here - it's reminding me of doing Maplin projects in the late 80s as a child. I can't get the long thin board at the bottom of the TV out - it looks like a major job and I can't see any test points on it (most of it is hidden behind the metal frame). I measured the resistance on the board going up the left hand side of the TV. There seemed to be resistance at all test points I could find: VS: 866ohm, OUTI: 866ohm, OUTL 866ohm: OUTH started in the high K ohms and steadily dropped, stabilising around 102.6kohm, VSCAN: started REALLY high in the mega ohms and then dropped stabilising around 136k ohm.

Am I testing correctly? Does any of the above offer any insight as to where I should go next please?

[holybob]

Re: Dead Samsung plasma - NOT (?) Power supply

Quick update - I've noticed on the 'dead' side of the power supply, I get various voltage readings on this side at the same time as the 'clicking' noise. The clicking seems to be coming from the component circled.

[dick_barton]

Re: Dead Samsung plasma - NOT (?) Power supply

The clicking noise from the transformer is just the power supply trying to switch on and then switching off.
The photo's are to small to read anything on the circuit board.

[dick_barton]

Re: Dead Samsung plasma - NOT (?) Power supply

There is a repair kit for this combined power supply/Zsus board and gives a hint to test "C4102, C4005 AND C4004 IF READING IS SHORT ACROSS THEM THEN THIS MEANS THIS IS THE RIGHT KIT FOR YOUR FAULT"

http://www.ebay.com/itm/SAMSUNG-PS43...-/332067823373

[holybob]

Re: Dead Samsung plasma - NOT (?) Power supply

Brilliant, thanks - I'll look in the morning. The strange thing is though that I have two power supplies showing exactly the same symptoms.

[dick_barton]

Re: Dead Samsung plasma - NOT (?) Power supply

It may not be the power supply. Because it's a combined power supply /Zsus board it may be that the board you replaced it with also had a fault although less likely.

If there's a fault on the Zsus, Ysus or one of the Ybuffers then it shuts down the power supply quickly to avoid any further damage.

Plasma's are not my thing, however there are more threads than you can read in a week on this forum regarding what and how to check.

[Andrew F. Ali]

Re: Dead Samsung plasma - NOT (?) Power supply

Most likely Y-sus and/or Z-sus Bd failure...PSU OK as you hear the 'clicks'...Disconnect PSU cable to Y-sus, power up the TV and see if Vs and Va at correct voltages come on at the correct voltages.

[holybob]

Re: Dead Samsung plasma - NOT (?) Power supply

I tested caps C4102, C4005 and C4004 on the power supply and they *don't* read short. So as I think we've concluded (thanks Andrew F. Ali and dick_barton) it isn't the power supply.

If I disconnect the PSU cable to the Y-sus, the Va and Vs voltages fire up to the correct voltages, and then slowly drop away (I guess this is expected behaviour).

So what not? Just buy myself a new Y-sus buffer board? I can get one off ebay for about £18 but I've already bought a power supply and logic board - pretty soon I'll have a complete set of boards ;-) Or is there anything I can check to be certain it *is* the y-sus ?

Thanks for all your assistance with this. It's becoming more a matter of principal getting this TV working again!!!!

[dick_barton]

Re: Dead Samsung plasma - NOT (?) Power supply

Not really knowing that much about plasma's other than what I read on this forum, perhaps some more experience repairers could advise you at this point.

[dicky96]

Re: Dead Samsung plasma - NOT (?) Power supply

Can you see any short circuits on the y-sus board, from power rails to 0V or Drain to Source shorts around the power FETs?

[holybob]

Re: Dead Samsung plasma - NOT (?) Power supply

Quick update - I didn't bother checking for shorts on the y-sus, just because I kind of thought I might as well order a new board anyway (£18) as my last chance saloon fix.

And I'm pleased to say that replacing the y-sus board instantly cured the problem. TV boots perfectly. What's slightly annoying is the new power supply I bought works, but is noisy as hell. I might try and return it. Thanks for your help everyone! Fixed without a soldering iron, just a bit of board swapping #welcometothemodernera

Bob