LG 50PQ6000 unstable 5v standby

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Looked at my only old PC PSU and there isnt one.

Found this online though?

Simple-Set your analog meter to X 10 K ohm range. Black probe to pin1 and red probe to pin 2 and 3 (must have readings) then black probe to pin 2 and red probe to pin 1 and 3 (must have readings). If black probe to pin 3 and red probe to pin 1 and 2-it should have no reading. If there is a reading then it is consider shorted. How acurate is this test? It is 90 over percent. That means, if you still suspicious about the reading then the only way is to direct replace the component and retest the smps again. This component is quite cheap and easily get from those used electronic board especially the SMPS that have the optoisolator in it.

Credit to jestineyoung.com

[tom66]

Re: LG 50PQ6000 unstable 5v standby

Not useful.
Only tests for leaky/short not failing reference.
Why don't you follow this thread - I'm helping heavymachines out with possible same issue:
https://www.badcaps.net/forum/showth...=24304&page=10

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Looked at my only old PC PSU and there isnt one.

Found this online though?

Simple-Set your analog meter to X 10 K ohm range. Black probe to pin1 and red probe to pin 2 and 3 (must have readings) then black probe to pin 2 and red probe to pin 1 and 3 (must have readings). If black probe to pin 3 and red probe to pin 1 and 2-it should have no reading. If there is a reading then it is consider shorted. How acurate is this test? It is 90 over percent. That means, if you still suspicious about the reading then the only way is to direct replace the component and retest the smps again. This component is quite cheap and easily get from those used electronic board especially the SMPS that have the optoisolator in it.

Credit to jestineyoung.com

Agreed didnt help me at all.

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Not useful.
Only tests for leaky/short not failing reference.
Why don't you follow this thread - I'm helping heavymachines out with possible same issue:
https://www.badcaps.net/forum/showth...=24304&page=10

Cool will do thanks

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Cool will do thanks

The link brought me back to this thread!

[tom66]

Re: LG 50PQ6000 unstable 5v standby

I mean here
https://www.badcaps.net/forum/showth...t=25670&page=4

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Cooleo! Cheers

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

I think I will get some in stock they seam a useful part to have in the draw.

Could you please tell me if the KIA431A is the same as the TL431A?

Data sheets below:





Ebay has some TL431A's easy to obtain thats all.

I have had a look and a few of the important looking numbers look close but not exact.

[tom66]

Re: LG 50PQ6000 unstable 5v standby

They appear to be compatible.

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Thanks Tom

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

I replaced 4 x TL431 but still a low stand by voltage.

I was lookng at this resistor and it was sutch a low resistance I couldnt check it??

Ps. have circuled a few bits.

[tom66]

Re: LG 50PQ6000 unstable 5v standby

Whats with that diode looks brown/burnt?

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Just been replaced with a new 1N4007. The original was shorted.

[tom66]

Re: LG 50PQ6000 unstable 5v standby

The old one was as 1N4007? Or was it UF4007?

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

Give me a min I will double check.

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

OK the original was an IN4007S 943 OR 1N4007S 943

Its very hard to read and I can find data sheets on them both. :/

The replacement is a: Silicon Rectifier Diode 1N4007 1 A 1000 V

[tom66]

Re: LG 50PQ6000 unstable 5v standby

It would be 1N4007S not IN4007S.
But anyway that's the right part.

Is the new part shorted in any way?
Does it measure 4.4V with main board unplugged?

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

New 1N4007 seams ok with diode test on DVM.

4.45vDC board unplugged.

[tom66]

Re: LG 50PQ6000 unstable 5v standby

OK, can you buy beg borrow or steal a 10 ohm 5W resistor? We need to see if P/S is stable under load.

[Baileybum1234]

Re: LG 50PQ6000 unstable 5v standby

I just happen to have 2 x 10 ohm 3w resistors in my hand.