PS51F8500 BN44-00619A power supply thermistor failure - but what else?

[T.F.]

Hello!

I was watching TV recently when it shut down while tripping the circuit
breaker. A couple of days later I removed the back panel, and, looking
at the PS module, I discovered a broken component, a thermistor. A bit
of it had split off and this fell into my hand while taking off the panel (see
photo, it's directly to the right hand side of that metal casing with the plug).
I'm not an expert by any means but I do think I can manage replacing it.
Question is, though, is this likely to be the entire issue, or will there be other
defective components which led to the thermistor breaking in the first place?
What do you recommend I should be looking at (and how)? The two fuses are
both fine.
Looking at similar such issues elsewhere as well as on YT it seems that the
FETs are a frequent cause of failure.

Decent multimeter and soldering equipment are on hand.

Thanks very much indeed for any assistance!

T.

Here's a stock photo:

[R_J]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

The thermistor went because the relay contacts are bad, sometimes you can get away with cleaning the contacts, but it's best to replace the relay.
Current flows through the thermistor in standby, but when the tv turns ON the relay shorts the thermistor.

[T.F.]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

The thermistor went because the relay contacts are bad, sometimes you can get away with cleaning the contacts, but it's best to replace the relay.
Current flows through the thermistor in standby, but when the tv turns ON the relay shorts the thermistor.

Thanks for the quick reply! Do you suppose that would solve it? Are there any other components I should be looking at (such as the FETs, which seem to be prone to failure and always included in "repair kits" I've seen on various sites?)?

T.

[R_J]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

Usually if the fets are shorted, the DC fuse will be blown. The ntc goes open because without the relay shorting it when the tv is ON, ALL the current is running through the ntc and it will eventually burn up and open.

[T.F.]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

Thanks for the help R_J. Besides having been busy looking for a
replacement TV, I've also been looking to procure those parts,
and it's quite difficult indeed. Apparently there's no local electronic
shops *at all* and there's no alternative to ordering them from China,
at least the relay (NTC seems to be available closer by).

What might likely happen if I were to (temporarily) replace the NTC only?

And what about (removing and) cleaning the relay contacts, as you say?
Could that be a temporary workaround?

Just out of curiousity, what would happen if you used a 13mm NTC instead
of a 15mm one (still 8 Ohms/5A)?

Thanks again!

[R_J]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

The smaller ntc will handle a bit less power but should not be an issue, Try cleaning the relay contacts, that should be ok, If you only replace the thermistor and the relay contacts are bad, when the tv is on and operating at full power, ALL the current will be passing through the thermistor and it will not handle it and it will burn up and open.

[Silidagreat]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

Hi,
I have the same problem with this board. Does anyone know what is the part number for that thermistor or does anyone have the diagram for this power board?
Please?

[R_J]

Re: PS51F8500 BN44-00619A power supply thermistor failure - but what else?

An SCK-056 (4.7Ω, 6A, 15mm) should work, If nothing else is bad I would suspect the relay contacts are bad and not shorting out the nt801s when the power supply is ON. (not in standby)