PSU Mystery

[Angry_Steel]

My Sister-in-Law called me a couple of days ago to tell me that her computer died, so I went to have a look expecting something simple like it usually is. But when I got there something was definitely wrong because it wouldnt even post. So taking the thing home with me I popped it open, and:

Test 1
Original PSU-Antec 380 + Intel XXXPESV board + Intel 2.8 P4

1. No Post
2. All fans power up
3. All voltages on all connectors are good including the ATX connector
4. Hard drives and DVD/CD drives will not spin up until the IDE connectors are removed, then they spin up fine.

Ok fair enough, sounds like a bad motherboard but Im not the trusting type so I grabbed another PSU from the closet and installed it.

Test 2
A-Open PSU + Intel XXXPESV board + Intel 2.8 P4

1. No Post
2. All Fans spin up
3. Hard drives and DVD/CD drives spin up fine.

Ok...so now I know we have a flaky motherboard at the very least, Im still not the trusting type so I move on to test 3 with my trusty test motherboard.

Test 3
Original PSU Antec 380 + Gigabyte G something + Duron 800

1. NO POST
2. All fans spin up

Ok right there Im having issues as I know this motherboard is working perfectly. I pull out the Antec and put in the other one and volla...everything boots up fine.

Im Stumped, all the voltages seem fine but something is wierded out on it, anyone have any clues?

[LPorc]

The only times I have similar experiences have been bad or aged capacitors on the motherboard power setup.

Try holding the reset for a little while powering up, if it keeps running and the drives start spinning, but it shuts down when you release the reset, it's the power caps on the motherboard.

[Angry_Steel]

Its most definitely the PSU as it did the same thing to the second Motherboard.

[bigben2k]

Troubleshooting 101; try adding the peripherals one by one; you might have a bad CD or HDD controller.

Sounds like the Antec gace up the ghost. You can measure the voltages all you want, but it's going to behave differently under load. It could be a bad connector, but not likely.

[RoboTech]

Two thoughts...

1. Check the Pwr-OK signal (typically gray wire on ATX coonector) going from the PSU to the mobo. Even if the PSU powers up all its rails, the mobo won't turn on unless it sees a +5V high signal from the PSU. If its not there then something is definately wrong with the PSU.

2. Check the main 20/25-pin (and 4-pin 12V aux) connector for burned pins or maybe a pin that has pushed out of the connector and is no longer making contact.

Good luck

[Angry_Steel]

The Pwr OK was .05 volts .....whats the normal voltage from it?

[Angry_Steel]

Originally Posted by RoboTech

Two thoughts...

1. Check the Pwr-OK signal (typically gray wire on ATX coonector) going from the PSU to the mobo. Even if the PSU powers up all its rails, the mobo won't turn on unless it sees a +5V high signal from the PSU.

Good call... Thanks. When I measured everything last night, that should have come out and hit me in the face with that .05 voltage but as I never have had any probs with the PWR Good I didnt even think about it. Its supposed to be a 5v

This is the last Antec I buy, used to use them all the time, but the one thats In my computer now Ive replaced 3 Caps in 2 years (550 TP) and this one I put in my Sis-In-Laws computer (380 TP) is only like 4months old.

Should just have her buy a new one instead of sending this one back for warranty, maybe Tagan or Fortron. I have a PC P&C sitting here in my next build but I doubt she wants to spend that kind of cash.

[bigben2k]

Yep. It's a standard TTL signal; it should read 0 (or near zero) or 5 volt.

[guandi]

I've had 2 Antec 550 TP's blow on me, one went first time i plugged it in it and the second one that replaced the first on warrenty blew up about a week later, never bought antec since.

Tagan are good, Enermax havent let me down yet but i have heard a few story's.

i have two Enlight PSU's that are damn near indestructable, one has been dropped down two flights of steps and only needed a cracked fan housing replaced and it now happily purrs away in this craptastic dell that falls to bits as i type.

oh, and dont buy an Ultra.