Samsung Plasma PSU BN44-00162a (0r 061A)

[nogger]

Hi all, just wondered if anyone has good experience repairing this PSU used in PS50Q97HDX & other plasma's.

Story so far:

I have a Sammy Plasma PSU BN4-00162A on the bench at the moment which blew its VS mosfets, 8Amp fuse etc . I changed them after checking the usual sub board components etc & also checked the VA tract & components. I powered up & strangely the VA tract now blew it's mosfets even though they all measured ok. Anyway, VA mosfets changed & surface mount & sub boards checked again & now i have the PSU runnning ok with correct VA voltages so now i just need to check the VS on the bench as i dont have a plasma in (just the board)

Problem is i can't seem to get this side fired up, does anyone know what the signal level (DC) is that the main logic board supplies to the PSU to fire up the VS tract . Checking the circuit (attached) the VS ON signal should fire QS812 which is a KRC101S NPN transistor designed for switching appls & according to the data sheet typical ON voltage is 1.5v-2.0 max. I made up a resistor chain off the 5.3 v DC rail to supply approx 1.7v & it still didn't want to fire up, any ideas anyone ?

Cheers
Graham

[tom66]

Re: Samsung Plasma PSU BN44-00162a (0r 061A)

Since it has integral base resistor, I would connect it direct to 5.3V and see if VS fires up.

Sometimes, it is necessary to turn on PSON first.

[nogger]

Re: Samsung Plasma PSU BN44-00162a (0r 061A)

Hi Tom thanks for the response.

Yes looking at the drawing again i think it's possible the resistor is dropping the volts too low to switch on. I ithink though i have tried it without success but i will give it another go. When you say sometimes you need PSON first i take it you mean the main PS ON which is the main on signal for all the secondary voltages & the VA ?. I have that enabled as it is, the test situation i am using is: PS ON enabled (grounded) & all secondary voltages present correct along with 63v VA. I just need to kick the VS into life & see if anything blows again :-) & i can get this out the door.

Graham

[nogger]

Re: Samsung Plasma PSU BN44-00162a (0r 061A)

Tried the 5.3v Tom but that doesnt work. I notice that on the VS tract the VS is enabled by 15volts being supplied to the small sub board which then pulses the mosfets & hence generates the output. The VA sub board is identical but the maximum it's getting is 3volts & then that drops so the mosfets never get fired. I think i iwll hook up an external PSU & pulse it with 2v & see if that works.
Graham

[rhodesrules]

Re: Samsung Plasma PSU BN44-00162a (0r 061A)

new here. Just need to post somewhere in order to be able to post my question. Sorry for the interruption.

[flocko]

Re: Samsung Plasma PSU BN44-00162a (0r 061A)

Hi you do not say you have you have 5v sby you need this for the board to work, as you have it on the a bench out of the set with the power cable just plugged in you should have 5vsby , then make Ps On low this will bring in the relay and power up Va /5.3/13v on the board when you have them you can then use the 5v sby to bring the Vs up Flocko