LG32LN5300 No standby voltage no power

[anupkg1985]

I'm working on LG power supply where I'm not getting any voltage on the board. I'm getting fluctuated voltage from 12v-15v on C103 on primary side. Also getting voltage fluctuations on pins of IC101. I replace all ceramics on primary side however same issue. Also tested mosfet Q101 looks good. Can some one tell me whats going wrong here?

[dick_barton]

Re: LG32LN5300 No standby voltage no power

What's the part number of the power supply. Pictures are difficult to read off.

[anupkg1985]

Re: LG32LN5300 No standby voltage no power

It's EAY62810301 Power Supply for LG 32 inch LED tv. C103 I'm getting fluctuating voltage on C103 is 100uf 50V which I already replaced and IC is SC1S311.

[dick_barton]

Re: LG32LN5300 No standby voltage no power

This may be the power supply schematic

Have you disconnected the mainboard from the power supply and used a 1K resistor between standby 3.5V and PWR then checked the voltages at the output?

[anupkg1985]

Re: LG32LN5300 No standby voltage no power

I'm not getting stand by 3.5V on the secondary side. Could that be IC issue?

[dick_barton]

Re: LG32LN5300 No standby voltage no power

It looks like SC1S311 is attempting to work but failing so trying again which is probably why the voltage is jumping around.
Here is the data sheet for SC1S311.
I would be checking that there is no physical damage to the IC and next check the components around it.

[dokma]

Re: LG32LN5300 No standby voltage no power

Try checking the R103 and ZD105 feeding the startup voltage to the IC101. If they are leaking, IC101 could be on the way out.

[anupkg1985]

Re: LG32LN5300 No standby voltage no power

I tested both r103 and zd105 and looks good to me.

[R_J]

Re: LG32LN5300 No standby voltage no power

Check that R113 is not open, It is likely the VCC voltage you are measuring could be from the startup cell in the ic itself. Check that R112 and the transformer winding are not open.
It is possible that the ic is bad as in no drive.