Acer H213H strange power issue

[jeanguy1980]

Very strange problem: monitor works for some days perfectly, then some days it won't power on at all. ( Completely no power).
I checked the cable, AC 240 input socket. All good. Capacitors look okay. I don't know what could cause this strange problem? thanks for suggestions or places to check...

 

[Nigel Goodwin]

You can't test capacitors visually, you need to test them using an ESR meter - it could be a duff electrolytic, it's by FAR the most common failing in switch-mode PSU's.

 

[jeanguy1980]

Thanks a lot for the quick feedback and suggestions. Unfortunately i don't have ESR meter at hand to test the Cs.
could faulty Capacitor cause this random power-on issue? sometimes it works, sometimes not. thanks again in advance.

 

[Nigel Goodwin]

Thanks a lot for the quick feedback and suggestions. Unfortunately i don't have ESR meter at hand to test the Cs.
could faulty Capacitor cause this random power-on issue? sometimes it works, sometimes not. thanks again in advance.

Yes, quite easily - a high ESR capacitor could be 'just on the edge' - so depending on various random factors might 'just' start up, or might 'just not start up. If there's a start-up resistor, that could have gone high as well (it used to be a pretty common fault), and again it could be 'on the edge'. A common issue used to be all was working fine until you turned it OFF (or there was a power cut), and then it wouldn't fire up again - because the startup circuit had failed.

 

[Nigel Goodwin]

I've just downloaded the service manual, the start-up resistors looks to be three in series (always a common cause of failure), R904, R905 and R906, all 10K. C908 or C939 would be good capacitors to check.

 

[jeanguy1980]

Thanks a lot.
But somehow I can't find those R C numbers you mentioned...could you please help pointing me to the right ones... thanks again

 

[Nigel Goodwin]

Looks like there's more than one version of that model then?.

 

[jeanguy1980]

hmmm..it appears so...what to do now?

 

[Nigel Goodwin]

hmmm..it appears so...what to do now?

Fault finding, for a start what voltages do you have on the rectifiers D701 and D702?.

 

[rjenkinsgb]

could you please help pointing me to the right ones...

Can you post a photo of the back of the PCB?