Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

[jczarniak]

Hi,
Replaced capacitors (4x1000uF), checked mosfets QX801, QX802, QS801, QS802 - no shorts, fuses OK.
AC connected:
5.1V between Stby and RTN pins
4.2V between PS-ON and RTN

AC connected, bridge between PS-ON and RTN:
Relays clicks ON and straight OFF.

No idea what to do / check next.
Thank you very much for any help.

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Mosfets: 11 Ohm between external legs on the bigger ones (QS801, QS802)
1380 Ohm - QX802 (between external legs)
2.4 kOhm - QX801
Anything wrong here, please?

[dick_barton]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Are those readings with the mosfet in circuit. Better to test with it removed and meter set to diode mode. What's its part number?

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Are those readings with the mosfet in circuit. Better to test with it removed and meter set to diode mode. What's its part number?

Mosfets still in board.
Checked in diode mode (still in board):
First one: 0.645, second one over the range.
Looks like these two has been replaced in the past.
FDPF 18N50T

[dick_barton]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

You should be able to measure the diode in one direction with all other measurements OL

[ReeceyBurger123]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Watch this if the mosfets are not blown, common issue on these boards is broken solder joints:

https://m.youtube.com/watch?v=JjQ--2SZdyY

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Removed two surface mounted diodes: DX803, DX804.
One looks fine, other one: over limit in diode mode, 5kOhm in resistance mode.
Power supply still clicks On and OFF without them diodes. Is this OK?

[ReeceyBurger123]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Removed two surface mounted diodes: DX803, DX804.
One looks fine, other one: over limit in diode mode, 5kOhm in resistance mode.
Power supply still clicks On and OFF without them diodes. Is this OK?

Thats fine, have you checked the solder joints on the devices on the middle heatsink ?

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Thats fine, have you checked the solder joints on the devices on the middle heatsink ?

Yes, re flowed etc...

[ReeceyBurger123]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Hmm ok then have you tried disconnecting the sustain boards see if the Psu stays on ?

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Yes.
I've got the power supply out of the TV now.
CN807 connector, stby, VS-on, PS-on pins; there are pins marked 5.3V, I've got only 1.42V. Is this OK?

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Connector CN801, AMP etc, on pins 5.3V and 12V I've got 1.4v.

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Va test point 1Volt

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Vg - 1.4 V
Vs - 0 V

[dick_barton]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Video at
https://youtu.be/za3EixgxBkk

Which may be of help.

[dick_barton]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

There's a repair kit available

http://www.coppelltvrepair.com/p/1/b...r-the-va-tract

[ReeceyBurger123]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Ok so your Vs supply is dead, as you said the fets were changed have you checked the fuse for them ?

[dick_barton]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Mosfets still in board.
Checked in diode mode (still in board):
First one: 0.645, second one over the range.
Looks like these two has been replaced in the past.
FDPF 18N50T

Both mosfets should show diode between D-S
Are you sure that the second mosfet is not open circuited.

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Ok so your Vs supply is dead, as you said the fets were changed have you checked the fuse for them ?

Fuse is fine

[jczarniak]

Re: Samsung PS42-Q97HD, power supply: BN44-00161A clicking ON and OFF

Both mosfets should show diode between D-S
Are you sure that the second mosfet is not open circuited.

Both mosfets:
red probe on S, black on D, diode mode, reading: 563
reversed probes: no readings on both mosfets.