Samsung HT-P38 DVD Home Theater System

[kevinm34232]

Re: Samsung HT-P38 DVD Home Theater System

Unfortunately due to my bad, Im not done with this one yet.. I was putting in the last screw in and screwdriver touched something and sparked in vicinity of power supply pic#3&4.

Standby red light is on but as soon as power is pressed it flashes blue for split second and then goes back to standby, no other voltages.

I thought I'd find something easily but after checking for awhile found nothing obviously shorted. The only thing I did find was a short between GND and SENSE on U7 (see page 54 for power supply schematic from post#2). It's a bit over my head but it looks like that goes to U10 Source

()

which may be where I touched, but U10 does not have a short between any pins. I need some help t/s'ing what I did here..

I have checked all the diodes, the 3 that showed short tested good out of circuit.

[kevinm34232]

Re: Samsung HT-P38 DVD Home Theater System

Wondering if I can get some help finding a replacement diode. I found D4 to be conducting in both directions and that's in the area where I touched. I had checked that diode before and it tested good so Im not sure if that's the only problem.
Diode is marked with FR107, I just want to make sure a get a correct replacement so if anyone can point me to one on Digikey I'd appreciate it.

[Khron]

Re: Samsung HT-P38 DVD Home Theater System

1A 1000v minimum, 500ns recovery time maximum.

Cheapest one Digikey has in stock would be this one:

http://www.digikey.fi/product-detail...SCT-ND/2233952

If i were you, just in case, i'd also pull and check the U4 FET. D4 is part of the RCD snubber that's supposed to "quiet down" the switching peaks in the primary of that flyback converter. With D4 shorted, that 100k resistor is in parallel with the primary transformer winding there, so it may well not be working as it's supposed to.

Also, that seems to be the part of the circuit that handles the transformer for all the logic and low-voltage audio circuitry, so... No small wonder it won't budge

[kevinm34232]

Re: Samsung HT-P38 DVD Home Theater System

Ok thanks for the diode! Can you show me as per the attached pic what you're saying about U4?

I'm still learning and trying to see how it flows from D4 to U4, or were you referring to U10? Thanks!

[Khron]

Re: Samsung HT-P38 DVD Home Theater System

Ah yes, U10, my bad - that's what you get for posting at 3:48am local time

[kevinm34232]

Re: Samsung HT-P38 DVD Home Theater System

That diode DID fix it (for the second time )... Thanks!

[Khron]

Re: Samsung HT-P38 DVD Home Theater System

Glad to hear that Gotta love "bringing back things from the dead", eh?