New power supply problem

J

Jeffman

Gawd
Joined
Jul 23, 2008
Messages
917
Hey,

My dad got a new power supply for his build. Specs are:

EVGA Z87 FTW motherboard
i5-4670 processor
EVGA 970 graphics card
16GB DDR3 RAM
240GB Corsair SSD
500GB Samsung SSD
Random SATA optical drive

Old power supply: Thermaltake TR2 RX 750
New power supply: Seasonic Focus Plus SSR-750FX

Everything worked fine on the old build. The power supply fan was a little loud, so he opted for the new one.

New one installed - computer won't POST. Popped old one back in, works fine. Okay, I told him likely just a bad power supply. He did an RMA. Got the replacement, he just plugged in motherboard and CPU cables, and computer appears to POST. Pulled old one out, put replacement in, won't POST again. Old one back in again, works fine.

He's sent that one back again, and has a Corsair on the way instead.

Is there some stupid thing I'm missing? I've installed hundreds of power supplies and never had one act like this. I've thought about it on and off and can't seem to come up with any reason that 2 power supplies wouldn't work on hardware that is working fine otherwise.
 
The "dumb checklist":

- Is the PSU on/off switch turned on?
- Is the 4 pin 12V connector plugged in? (Sometimes I plug in the main ATX connector GPU and 5v connectors and forget this one)
- Verify the PSU is working independently using the "paperclip test"?
- Are you absolutely sure all the connectors were inserted the correct way, not backwards?

I would even clear the CMOS on your motherboard, it may have some weird voltage memory from the old PSU that keeps it from POSTing with the new one
 
janas19 said:
The "dumb checklist":

- Is the PSU on/off switch turned on?
- Is the 4 pin 12V connector plugged in? (Sometimes I plug in the main ATX connector GPU and 5v connectors and forget this one)
- Verify the PSU is working independently using the "paperclip test"?
- Are you absolutely sure all the connectors were inserted the correct way, not backwards?

I would even clear the CMOS on your motherboard, it may have some weird voltage memory from the old PSU that keeps it from POSTing with the new one
Click to expand...

^Yes to most.

He didn't do the paperclip test. Really wouldn't matter much, either it works in the computer or it doesn't. I figured the first power supply was dead. Didn't know what to think when the second one didn't work. Since the old one has always worked he just went back to it each time.

CMOS was cleared the first time, by accident. Turns out the motherboard battery was dead. That's been resolved.

I'm just wondering if there's any incompatibility that I'm unaware of. I wouldn't think so...but who knows?
 
Last edited:
I have had a bad optical drive cause this, turned out it was triggering the protection in the PSU. Maybe the old one has less sensitive protections.
 
vick1000 said:
I have had a bad optical drive cause this, turned out it was triggering the protection in the PSU. Maybe the old one has less sensitive protections.
Click to expand...

Really? I'm going up to see him on Sunday (It's a 3 hour drive). I'll check this out. He got the new Corsair power supply about a week ago, but he doesn't want to try it until I'm there.
 
Yes! The new Corsair worked with no problems.

It's left me wondering if the Seasonic power supplies he tried were actually defective, or if he was doing something wrong. He's pretty smart (he got me on a good start to PC building about 20 years ago), so I don't think he messed it up. He hasn't done much computer work in the last 10 years so maybe he was rusty.
 
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