problem with psu in Samsung 32"

[katinkapicinyke]

Re: problem with psu in Samsung 32"

Check DB801,DB802.

Thank you! Both de-soldered and checked, appeared to be working correctly.

[R_J]

Re: problem with psu in Samsung 32"

Thank you, I can see no short on CP811, CP805 (took me some time to find, little SMD bugger!), neither on CP805, CM807, nor on CM814.

The resistance between the two legs of CP811 is around 4.5K Ohm, give or take due to my meters tolerance.

I suspect the transistor must be bad, (open). you should be able to find a NPN transistor to install just to try it.
It acts like a switched, regulator for the M_VCC voltage.

[katinkapicinyke]

Re: problem with psu in Samsung 32"

I suspect the transistor must be bad, (open). you should be able to find a NPN transistor to install just to try it.
It acts like a switched, regulator for the M_VCC voltage.

One of those moments in life, when one only has a PNP in hand...
I found a TIP117 in my box of spares, could I just use that instead?

[R_J]

Re: problem with psu in Samsung 32"

You can not use a PNP where an NPN is in the circuit. It won't work.

[katinkapicinyke]

Re: problem with psu in Samsung 32"

You can not use a PNP where an NPN is in the circuit. It won't work.

Understood, thank you.

I've found a BD243B (NPN), would that be sufficient please?

[dick_barton]

Re: problem with psu in Samsung 32"

What is the part number on the existing transistor QB802 ? Is it metal or plastic backed and does it connect to a heatsink?

Edit
If it's a KSD526-D then BD243B looks suitable

[katinkapicinyke]

Re: problem with psu in Samsung 32"

What is the part number on the existing transistor QB802 ? Is it metal or plastic backed and does it connect to a heatsink?

Edit
If it's a KSD526-D then BD243B looks suitable

Thank you, yes, it is a metal backed To-220 as far as I can tell with no heatsink attached (KSD526-D).

[katinkapicinyke]

Re: problem with psu in Samsung 32"

Reporting back here chaps, issue fixed with replacing KSD526-Y with a BD243B NPN transistor, the PSU is back in business!

All your efforts are greatly appreciated, thank you once again!

[dick_barton]

Re: problem with psu in Samsung 32"

Thanks for the feedback.