LG 42LN5400 no standby.

[budm]

Re: LG 42LN5400 no standby.

Which cap is that one on the board, c???

[diif]

Re: LG 42LN5400 no standby.

C102

[dick_barton]

Re: LG 42LN5400 no standby.

Good luck when it arrives.

[diif]

Re: LG 42LN5400 no standby.

I've fitted the cap but i'm still getting the enable voltage fluctuating and too low.
I'm missing something...

[diif]

Re: LG 42LN5400 no standby.

Seems the cap is a 3kv not a 1kv. Is that going to make a difference ?

[budm]

Re: LG 42LN5400 no standby.

Not the cap Voltage problem, you still have other problem in the circuit.

[diif]

Re: LG 42LN5400 no standby.

I'm struggling to see what though. I've removed all of the mosfets and caps and pulled up a leg on the diodes and resistors and they all measure fine.

[dick_barton]

Re: LG 42LN5400 no standby.

What voltages are you measuring with everything connected and powered up as shown in the box???

[dick_barton]

Re: LG 42LN5400 no standby.

Also what voltages do you have at the various pins as shown in the attachment. You also need to make sure that the chain of resistors attached to pin 4 are exactly as they should be.

[diif]

Re: LG 42LN5400 no standby.

There are no voltages present on that connector with everything connected

With just the PSU receiving power the voltages on the SSC1S311 are

1) 316mv
2) 0v
3) NC
4) 266v
5) 0v
6) 0v
7) 11-14v fluctuating
8) 0v

I do find 2.5v on Q802 though, I wonder if this is a low standby voltage ?

[dick_barton]

Re: LG 42LN5400 no standby.

OK so no secondary voltages.
Resistances leading to Pin 4 all checked ?

IC Pin4 nice high voltage but don't know if its's what is should be

Suggest you change the IC.

[budm]

Re: LG 42LN5400 no standby.

Did you find and replace the start up cap that is connected to the VCC pin? You are sure that it is C103?
Per spec of the IC, the Vstart (Vs) is between 18~24V, 21V typ.
I suspect the IC as well, but you should also check the rectifer in the secondary side to make sure they are not shorted.

[diif]

Re: LG 42LN5400 no standby.

Thank you, I appreciate the help.

Yes, pulled the legs on all of the resistors and diodes to check.

Is the startup cap C108 ? 0.1uF 50v ? It's a tiny ceramic cap i have no way of measuring.
Could you help me identify the rectifier on the secondary side please.

[budm]

Re: LG 42LN5400 no standby.

OK, you have the diagram, I wish we get to see that from the beginning.
C103 is the startup/running cap.
Per diagram: Rectifiers in the secondary cold side are D201 (for standby +B24 which feeds the switched 24V) , D204 (for standby 85V DD), D203 and D205 for the 3.5V STBY.

[dick_barton]

Re: LG 42LN5400 no standby.

start testing D201, D203, D204, D205 to start with. Have you checked C103, D102, D103, ZD103, Where did the schematic appear from?

[diif]

Re: LG 42LN5400 no standby.

Apologies, I only found it yesterday when I was at work and have just pulled it off my laptop. I did try and find it when i started with no luck.

C103 99.4uF 0.06ohms

With the diode setting on multimeter
D201 0.327v
D203 0.175v
D204 0.404v
D205 0.208v
D102 0.488v
ZD102 0.496v

[dick_barton]

Re: LG 42LN5400 no standby.

Those readings appear to be OK. Did you also test the diodes with the leads reversed to ensure they read high or OL on your meter.

[ReeceyBurger123]

Re: LG 42LN5400 no standby.

Think I read something about the Smps controller for these failing. Will see if I can find it then will link it.

[diif]

Re: LG 42LN5400 no standby.

Those readings appear to be OK. Did you also test the diodes with the leads reversed to ensure they read high or OL on your meter.

Thanks, yes either started high, rising to OL or just OL.

Think I read something about the Smps controller for these failing. Will see if I can find it then will link it.

Cheers mate.

IC101 SSC1S311A as suggested by budm and dick_barton ?

[ppx2006]

Re: LG 42LN5400 no standby.

Hi,Diif

I have the same problem with Power Supply of my LG 32LN575N, did you resolve the issue?

Thanks.
ppx