Samsung 460CXN - Power Supply Issue

[R_J]

Re: Samsung 460CXN - Power Supply Issue

QP802s and QP801S are basically switches, they are turned on and off by the signal on their gates (pulsed at 65Khz) They are normally open.
Turning them on and off causes the voltage on this side of TM802S coil to be boosted from 160 volts supplied by the bridge to around 300 volts dc across CP810/CP817
Since the bad fet is shorted to the gate it might be wise to also replace UP801

[pantherts]

Re: Samsung 460CXN - Power Supply Issue

Resistance between source and drain on QP802S is an OL.

[pantherts]

Re: Samsung 460CXN - Power Supply Issue

Okay, I understand now. That makes sense. Thanks so much for the explanation.

[pantherts]

Re: Samsung 460CXN - Power Supply Issue

Any way to reliably test UP801 in power off mode to see if it's shorted inside?

[R_J]

Re: Samsung 460CXN - Power Supply Issue

got a scope to check the output pulse? it might be ok but if it is not you could blow the fets or the supply just won't work

[pantherts]

Re: Samsung 460CXN - Power Supply Issue

Nah, no scope available. Alright, I'll get an order together. Thanks so much for your assistance with this. I'll check back in again.