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Fault CX500, why is it now working ?


Matt35636

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Hello, I'm curious if anyone has attempted to fix a Corsair PSU... I have a CX500 and it had a power on issue which seemed like a "typical capacitor" issue.

So silly me decided to open it up & void my warranty.

 

It always provided the 3 power rails, but does not turn on the POWER_OK pin when its "warm", unfortunately it needed to be switched off over night for it to correctly power on once.

 

Visibly it "looks" like the CapXon cap's are fine. But I'm concerned about the PS229 power monitor IC. It does not send out +5 on the POWER_OK pin. (on a warm boot), and it sets the fault pin... so it knows there's a problem. But all the rail voltages/ripple seem good to me.... I don't have a digital scope, so I can not capture the rise times.

All the voltages on the IC pins are the same, if its working or not (except PWR_OK & FAULT)

 

 

I found that putting a large load (car head light) on the 12v rail, does power up.

 

In the picture attachment (I adjusted the example datasheet to fit this power supply). I though that adding a large capacitor between pins 1 & 2 (PowerGoodInput & Ground) would help delay the IC startup (there is a great block diagram), but it made it worse!. So I took the risk and removed the smd capacitor (circled in red) and now it works just fine.

 

Its appears that they have built the board from the example application from an earlier chip (PS222 ?). But physically used the newer chip (PS229).

 

 

SO...

I was wondering if anyone has explored this issue. And possibly knows why this little cap makes the difference.

P.S. Please no comments about Capacitor brands :)

ps229.png.e459059a7de28960d13b8f56d59d0128.png

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