HP Compaq: DOA - Obvious Things To Check?

[(PeteCresswell)]

I just posted this in the Windows Vista NG, but then realized that I might have a better chance here. ===================================================================

Family members HP Compaq/Older Athlon X2 just went belly-up.

Only sign of life is a single green led glowing on the mobo: no power supply fan, no CPU fan, no response to DVD drive's eject button...

First thought was power supply, but when I swapped in a known good power supply, no change.

Then I figured "Maybe the on/off switch"... so I pulled out the switch and used a knife to jumper the two leads coming into it - figuring that would duplicate the action of the switch... but no luck there either.

Unless somebody has a better idea, next thing I am going to do is to revisit the power supply and verify correct voltage on each output lead.

[mike]

If the power supply fan ain't running, it's likely somewhere in that path. Pull the power cable and short the "on" pin to ground. Pinouts.ru will show you which pin that is for your particular configuration. If the PS fan runs, start from the switch and check all the connections down to the header. Not much you can do in between.

I had a system similar to that. Power switch didn't work. Grounding the pin brought up the PS. That path goes thru one of the huge glue chips on a multilayer board that's impossible to debug. Nothing but the chip in the path.

[Don Y]

Examine the (electrolytic) capacitors on the motherboard (and inside the power supply) for "bulges"/leaks. The tops of the caps will appear "domed" (instead of perfectly *flat*) when they have failed. You may also notice a brownish residue on the top *or* leaking from the bottom. Sometimes, the cap will have lifted off the circuit board and tilted as it "vented" ("blew its wad").

[philo]

If it did the same with a known good supply then I would not suspect the original.

First thing I'd do is reset the CMOS (using the jumper)

Next, remove all components including RAM etc...if the mobo is good, you should at least hear the RAM error beeps.

Then start putting things back to see what the problem is.

Occasionally problems are as simple as cleaning the pins on the RAM etc.

If still, nothing the mobo is probably bad but in a few extremely rare circumstances I have once found all I had to do was remove then replace the CPU.

Also once I found the CMOS battery was low but not all the way dead (approx 2.2 v) and put the mobo in an illogical state (

[philo]

Yep. If I see bad caps, I condemn the mobo and go no further.

[(PeteCresswell)]

Per philo:

I was not ruling out RCI on my part - my assumption having been that if the connectors plug into the mobo, it must be the right kind of PS.

[clare]

Look at all the caps on the mobo. Any that are convex on the top?? Sounds to me like the mobo is shorted due to bad caps (very common problem - particularly if it's been running a bit slow lately)

[philo]

That's correct.

Possibly 15 years ago, Dell had a non-standard ATX configuration but I am sure that does not apply.

BTW: Might was well look at the pins on the mobo, if they are badly tarnished or burned looking ...no need to go further.

[rbowman]

The newer power supplies are deceptive.

You need the jumper before the power supply itself fires up. The last time I had a problem that didn't trace back to a defective supply it was a bad floppy drive.

[(PeteCresswell)]

Per (PeteCresswell):

Bingo! Either RCI or a bad second PSU.

Put in another PSU and it came right up.

After, if course, I had hosed the BIOS settings by replacing the CMOS battery - just on GPs... -)

[philo]

In your first post you said "known good"

Sheesh, what are you, a human being :)

[(PeteCresswell)]

Per Oren:

No - same, cannibalized from an old PC.

[(PeteCresswell)]

Per philo:

RCI strikes again.

But it did come out of a new box... my guess is that there was some incompatibility that I did not know enough to recognize.

I put it back with a note on the box "Suspect..."...

[bob_villain]

I replaced a Dell P/S that checked good with a tester...the guy at the repair shop said a standard replacement wouldn't work. I did go back and tell him it worked fine in the Dell.

[Wade Garrett]

Given the rock bottom price of entry level-- or even refurb-- computers these days, I'd bury it with full honors and go buy a new one;-)

[philo]

What is RCI?

I should have asked sooner

Unless the power switch somehow got flipped to 220v

I've seen that on a few very rare occasions

[(PeteCresswell)]

Per philo:

I was trolling....

It is a sophisticated technical term developed by my group during the mainframe user support days: Recto-Cranial Inversion..... -)

[bob_villain]

[mike]

I've read reports that, for a while, Dell used a different pinout on their power supplies. I've never encountered one in the wild.

[philo]

I should have known

HA!