Samsung ps42b451 clicking psu

[Liam]

Hi guys

Plasma TV - ps42b451
Psu - bn44-00273d

Just received this plasma TV this morning. I've worked in a few of these before, the fault is that it's not powering up. Clicks 5 times then stops, all caps seem ok, fets 801 and 802 seem ok.

Does exactly the same with y-sus and z-sus disconnected.

Cn801 connection to main board-
Ps_on is at 3.3v
Std5v is at 5.2v
No other voltages because psu won't power on.

Cn802 connection to logic board -
Vs_on at 0v jumping to 3.3 whilst trying to turn on (clicking)
Ps_on also at 0v jumping to 3.3 whilst trying to turn on (clicking)
Gnd
Gnd
D5.3v is at 5.2
D5.3v is at 5.2

No visible cracks on solder anywhere

I need to figure out if psu is at fault or the main board is stopping this from powering on.

Any help guys??

[downunder]

Hi Liam,

There are definitely no dry joints on QX801/2? It's the usual cause.

Otherwise set up the power supply on the bench. Connect PS-ON (pin 1-CN801) to STB-5V (pin3-CN801) via a 100 ohm resistor. Do the same with VS-ON (pin 2-CN801). Hook it up to mains and see if the power supply continues to click, or turns on and generates voltages.

If it turns on, logic board is suspect, but it could also be the main board.                    Bruce

PS: Turnip will be dissecting this for grammatical and punctuation errors.

[Liam]

Right I've had the psu on the bench.
Managed to trick ps_on
Then trick vs_on using resistors and its clicking just like when the main board and the logic board is connected which I think rules out both them boards so I'm guessing it's a psu fault

But struggling to pin point the fault in the psu, it's very clean and no visible dry joints at all :(

[downunder]

Well, I'd say definitely the power supply then. Over to you now. You'll have to go over it again, unless some other member has some advice to offer.                 Bruce

[Turnip]

Hi Bruce, and not at all.

Will Shakespeare spelled his name differently most every day, and he gave Richard 3rd rather bad press due mostly to a deformity of the spine, but us Brits now have them bent bones sorted, real tasty.

Mine were always dries on 801/2 - Makes it the only Plasma I almost, nearly like - well, a soupcon.

Mind you, there were those Bush badged Sammies where the panel was always duff, and mending folks made the pound from a printed 'Certificate of Crap' - Chris.

[downunder]

Chris, your vernacular is music to the ears. If we Aussies had half a brain, we'd be classed as 'gifted'.

Bruce

[Turnip]

Hi Bruce,

Note that Quuq currently doesn't have the category 'Gifted' above our current rating for pure persistence, so would suggest that you, and a couple of other notables - Natch not me, should be elevated to such a status.

Seem to recall Quuq had 'Super Heroes' but they seem a bit quiescent at present, doubtless due to pressure of business - Suggest a vote, maybe, as us Brits are about to do something similar, if we can discern any differences when main parties stick rigidly to the centre ground, and Ukip is totally daft - Chris.