seiki se55uy04 Blown PSU 890-pf0-5501

[Aviator747]

Hi Everyone,

A friend of mine gave me this 55" LCD Tv as it died with a "poof" of magic smoke.

When I plugged it in to see what state it was in, it did nothing, no response to any panel input or remote input. no back light or led indicators.

I yanked off the back cover and noticed a disc cap looking component, with a NTC 3D-15 pn# on it. This is apparently a thermistor. On the underside there is a very severe scorch mark and some traces are blown away. This is where part of the problem arises. I can tell where one side of the thermistor connects to its trace. But not the other side.

There is also a cap that has splooged out its contents. I'm not 100% sure as to what type it is or what value it is. I haven't removed it or the silicone that stabilizes it.

I have found this board several places online, everyone is sold out. Or wants big bucks for a used unit. If I could find the board cheap enough I would swap it out. Or find a schematic or a underside picture to determine where the thermistor connects too.

Thanks for any input.

[CapLeaker]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

The thermistor goes between the 2 inductors. Figure out what else is blown, open, or shorted. Check F101, bridge rectifier and all the fets and diodes mounted on the heat sink in the primary section. All that black (burnt mark) would have to be totally removed an the board fixed, as the black stuff is conductive. If the fets are shorted to the gate pin, then you would have to look at the PFC and the gate drive circuit as well. The the next thing to figure out would be if all the voltage rails on the secondary are o.k.

[Aviator747]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

99% alcohol would be the best for cleaning up all the carbon char? What's the best way to check with a VOM? Someday I would like to get a LC tester. The diodes I should be able to test in circuit with diode check. Whats the best way for the fets? Can it be done in circuit?

Thanks for responding

[CapLeaker]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

Yeah, you need alcohol, but you also need to grind the rest of the black stuff off until it is gone. It won't all wipe away.

[CapLeaker]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

test away with your meter in diode mode and go for shorts on the fets and diodes. Test it in circuit, if it is shorted, test it out of circuit again.

[stjeff0]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

That cheap solder. Replacing that thermistor worked for us twice now. No other service needed.

[brianbelfast]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

Hello old thread. Does anyone have a schematic for this PSU? I have a dead one. Blowing fuses. The PFC controller has shit itself and killed the FET.

[CapLeaker]

Re: seiki se55uy04 Blown PSU 890-pf0-5501

Change the PWM and the FET, check the diodes and resistors on the primary.