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Old 10-01-2021, 10:19 AM   #14
ohren
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Join Date: Mar 2015
City & State: Sweden
My Country: Sweden
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Posts: 59
Default Re: Dell 2209wa - momentarily blinks every two seconds [ Video + Audio + Service Manu

I isolated the problem.

Turns out the PFC + PWM controller is overheating. Alcohol sizzles on it, and the problem goes away for a while.

Before potentially replacing it the question is whether this is more likely because of internal deterioration, or failure of an external component. I'd be grateful if someone could lend me their intuition:

1. Do these controllers commonly get very hot during normal operation? I'm not sure why that would be, but if so, could that sufficiently explain internal deterioration?

2. Would the failure of some external component commonly be able to make such a controller draw too much power?

Maybe the controller is on its way out, but until then I've stuck a heatsink on it to see what happens. Looks promising so far. Still, I can feel it radiate heat far more than anything else on the board. The heat sink is at about 70 C according to an IR thermometer.

The circuit can be found on page 75 (U850). The controller is an SG6901ASZ.
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