LG W1941s strange problem

[terry]

I have a strange PSU fault on this monitor, the monitor turns on and works for about 5 mins, then the PSU shuts down (no power from the yellow transformer). After about 1 min the monitor restarts itself. and it just keeps doing this 5 mins turns off then 1 min turns on. I removed the Rectifier as shown in the picture and connected a test PSU to these point, the monitor works fine.

So I think the fault must be with the main side of the PSU.

I have already replaced the yellow transformer and the Rectifier but still have the same problem

[terry]

Re: LG W1941s strange problem

added more pictures

[1supertech]

Re: LG W1941s strange problem

Test all capacitors with ESR meter if you don't have an ESR meter replace all caps but the big fat one are those diodes test good.

[terry]

Re: LG W1941s strange problem

Yes the diodes are good, I have replaced all the cap still the same problem. I did replace the large main cap just to make sure.

[ben7]

Re: LG W1941s strange problem

Try some freeze spray on IC802 when the monitor shuts off. If it turns back on right away, then the chip is likely overheating, or is defective.

[terry]

Re: LG W1941s strange problem

Thanks Ben, I have just tried the freeze spray and the monitor turns on right away. I will order a new chip and that should sort out the problem.

[terry]

Re: LG W1941s strange problem

I have got fitted the new chip (TOP258PN) and now working great.

Thanks for your help