Help with defective (?) power supply

[xylem]

I got a new power supply, which has an odd quirk, and i'd like to see if its repairable before dealing with RMA. I've opened many power supplies, and performed mods, so if anyone knows what i might do to fix this myself, i'd appreciate the info.

Symptom: If this machine has been powered off for a while, after it is powered on for a brief period of time (~4 minutes?) it seems like the psu just cuts A/C power... i hear the hard drives shut down, followed by the entire machine blackout .5-1 second later. I then have to power it up again, and this second time, the machine will run indefinitely with no interruptions.

I'm inclined to think it's heat-related... as if some sensor in the psu is improperly detecting temperature, or a temperature differential between boot temperature and current temperature.

Any ideas?

 

[JEDIYoda]

why do you think its the PSU??? The PSU as you stated is new.....
To be heat related the PSU would have to be on for more than just a few minutes. Would it not?

 

[xylem]

Originally posted by: JEDIYoda
why do you think its the PSU??? The PSU as you stated is new.....
To be heat related the PSU would have to be on for more than just a few minutes. Would it not?

I just installed this psu, and it's the only thing i replaced. It happened the first time i powered on using it, and has happened every time since. It seems strange to me, but it happens after the machine has been off for a while (and has had a chance to cool down... maybe also had a chance to discharge the capacitors, but i'm not sure how that would cause this). Once i restart that single time, it will run indefinitely.

 

[John]

Swap with a known good psu and see what happens.

 

[Reiginsei]

I have the same problem with a Seasonic 650w PSU.

If the machine has been turned off for a long period of time, and then you press the power button, the comp turns on and then turns off a few seconds later. Then, when you press the power button, the comp can stay on forever (I turn off the comp once a week.)

Unfortunately, I can't test the voltage of the PSU in MS Vista 64 because Intel desktop utils don't work. In the BIOS, the voltages look fine though.

 

[GalvanizedYankee]

Originally posted by: John
Swap with a known good psu and see what happens.

Do this.

The new PSU may have a dry capacitor. When powered on several times a dry cap will warm up and start to function. When cold it will offer an open or high resistance circuit.
You could warm up the PSU with a hair dryer set on low(blow into the exhaust grill), then boot the rig. If it powers on w/o issue, it most certainly will be a defective cap. Main boards are forced to POST by warming the caps, then diagnostics can be run to see if it is worth repair.

It would be very odd for a high-end PSU like Seasonic to have a problem like this but a Deer or L&C...They are Chinese Junk(boat) when new.

xylem,
You failed to indicate brand and model of your PSU.

 

[NeoPTLD]

I would do nothing other than trying a known good PSU and if the problem is resolved, don't tamper with it.

Return the new power supply for repair/refund.