Re: New PSU, New MOBO No power


OK. Got it. Thank you for your help. The 'new' mobo was bad. I pulled an
old mobo from an old Dell, plugged everything into their sockets and it fired
right up! WHO would have thought THAT!!!????

Good grief .. what a waste of two days! :)

Have a wonderful new year everyone and thanks for your help.

Don in Tucson
AizA


"AizAizA" wrote:

Thank you for the suggestion. I pulled the mobo, plugged in only 20 pin and
12vdc then shorted the power on pins. No change in symptoms. :( I thought
fer sher you had come up with the answer. I even shorted pins like for front
LEDS to see if THEY would come on .. nope.
I double checked power in with psu tester; still good.
Again thank you.

--Still Stuck in Tucson
AizA

"Michael W. Ryder" wrote:

AizAizA wrote:
Thank you for reviewing this post. I am a pretty experienced tech, which is
why I have ended up here .. I need some wisdom from Super Techs.
Here is situation: Got computer (HP Pavillion a300n) that does nothing when
power switch pressed.
Pulled PSU, replaced with suspected good PSU (used).
Pressed power switch .... power light came on, fans whirred .. and within
seconds power switch light dimmed to nothing and then POP goes the PSU.
Got NEW PSU and plugged in everything, held breath and hit power switch.
Nothing.
Bought new mobo. Plugged everything in and pressed power switch. Nothing.
Unplugged peripherals (hard drive, A drive, CD rom) hit power switch.
Nothing.
Grabbed PSU tester, plugged it in. All lights indicate good.
Plugged in HD, CD, and A drive, leaving 12VDC and 20 pin plugged into
tester. PSU fan whirs. Plugged 12VDC into mobo. PSU fans whir.
Plugged in 20 pin and nothing.
Replaced CPU.
Still nothing.
Checked front panel cable with multimeter .. switch works.
Even tried shorting power on pins on mobo.
Nothing.
I have even gone so far as to plug in PSU to mobo (12vdc and 20 pin) and
have EVERYTHING else unplugged ... even mouse, monitor and keyboard.
Nothing.
I have checked (and rechecked) 115 switch.
Given that power supply tester shows good power out, I know switch and power
cord are good.
Known good psu, brand new mobo, no loads plugged in and I still get nothing.
No fans, no lights, no action at all.
I replaced with previous mobo and CPU.
Nothing.
I even swore at it.
Nothing.
What in the WORLD am I missing????????
I know I am a pretty brigh tech .. have worked in electronics
troubleshooting for decades. I know I have followed every normal
troubleshooting practice more than once on this machine. (I am on Day Three
with this struggle)
PLEASE assist. PLEASE tell me where I am making my mistake.
I also grabbed another new PSU in case the other one had OK volts, but not
enough current.
I do not believe that I am missing a 'normal' thing like power supply switch
in the wrong position or something like that. I have gone through all the
basics.
I am open to any advice and I welcome any ideas or words of wisdom from
those of you with greater experience and knowledge than I.
I am grate ful that you took the time to read this, and thankful for your
responses.
Have a wonderful 2007.

Don in Tucson
AizA

Have you tried powering up the motherboard out of the case? Maybe you
have a short between motherboard and case, like a misplaced standoff.

.

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