New PSU and now problems

[SanDiegoPC]

I posted last week RE: an HP Pavilion a430n desktop. I did replace the PSU with a Thermaltake 450W unit which should have been a great upgrade from the original junk that it came with.

When I started it up, I got right to the Windows password screen so I released it to the customer. He calls me up and says then, that he can't get into Windows at all after he gets it home.

I have it on my bench now and can't get jack out of it. Odd thing is that when you turn on the switch at the back of the PSU, the computer comes on.... just as if you had pushed the button on the front of the machine. I know that Dells and HP computers usually spin the fans for abouit a second or so when plugged in, but that's not what this one's doing. It tries to start the computer into the POST sequence. Problem is that it gives no video 9 times outta 10.

The front panel switch is not shorted. If you hold it for 5 sec you can shut it down. Then touching the switch again fires the machine up. So the front panel switch is working as it should. Why does the machine start up though, when you first plug it in?

I tried another video card too, and got nothing in the monitor then either. So there's two issues: 1 is that it comes on as soon as you plug it in, 2 is that there's no video 9 times out of 10 when it starts.

HELP!

 

[PCTC2]

IIRC some Dells and HPs don't use the standard ATX form-factor 20-pin so the pins may not be the correct order, thus shorting the power pin to ground, making the PSU try to turn on.

 

[SanDiegoPC]

Thanks. so what's IIRC? I have by the way, replaced PSU's in about thirty Dells and half that many Emachines...this is the first I have had a problem. What can I do?

 

[Flipped Gazelle]

Originally posted by: SanDiegoPC
Thanks. so what's IIRC? I have by the way, replaced PSU's in about thirty Dells and half that many Emachines...this is the first I have had a problem. What can I do?

IIRC = If I Recall Correctly

The issue with the Dell PSU's was several years ago. Basically, they were wired slightly differently, so plugging in an off-the-shelf PSU resulted in either the PC not working, or the PC shorting out.

Have you tried a different PSU with the problematic PC?

You should definitely do more testing on a repaired/upgraded PC that just booting to login screen.

 

[SanDiegoPC]

Yes, I have tried another PSU. Exact same result unfortunately. Both of them have much more power than the OEM one so I know that's not an issue. Both PSU's and the HD from this computer all work well in another machine.

I agree about testing a repaired PC ... no question about that. But I didnt' have his password and had already removed it from the bench to work on another. Customer called and asked about it, I made the mistake of telling him to come & get it rather than asking for his PW.