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Power supply questions:

A power supply on one of my computers recently failed. ( I know it is the supply. I yanked another supply out of another computer, and this computer runs fine. I tried this supply in the other computer and it wont run. )

A freind had an Compaq he wanted to throw out, so he gave it to me. The mobo connector on the power supply was correct but the leads in were the wrong color ( except for ground ). He also had a repair manual, the voltages it described matched the voltages in the ATX spec.

So I attached a few old hard drives and fans to the power supply ( for a load ) and tried grounding the power on line. It wouldn't turn on.

I then yanked the Compaq mobo, attached the power supply to the mobo, and turned it on. With the back exposed, I measured the voltages on each of the current carrying lines and they matched.

I temporarily put in the power supply, and plugged it in. The computer came on when I plugged the supply into the 120, didn't have to push the button.

So now I'm confused.

Before I install the PS, I will have to take the connector from the old PS and wire it into the Compaq PS ( the leads on the connector are way short, the form factor of the supply seems off in that regard ).

Here are the differences that I have noted in the manual and the ATX standard.

Differnce one. A lead labeld Fan off on the Compaq is label PowerOK in the ATX spec. Difference two. One of the ground leads is specified as remote sensing on the Compaq. none are specified that way in the ATX standard. Difference three. One of the 3.3 leads is specified as remote sensing in both the Compaq and the ATX standard.

I have no idea what remote sensing means in this case. Should I change those leads? Should I not use the remote sensing ground lead?

Would that explain the power on without abutton push? Thanks.

The reply-to email address is snipped-for-privacy@yahoo.com. This is an address I ignore. To reply via email, remove 2002 and change yahoo to interaccess,

** Thaddeus L. Olczyk, PhD

There is a difference between

*thinking* you know something, and *knowing* you know something.
Reply to
TLOlczyk
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The problem is powerok also know as 'power good'. The motherboard outputs a signal to this input within a specific time frame or the ATX will shut off. If the motherboard does not provide this signal, you can jumper it to a 5 volt output. Lack of the power good signal is why you must keep the switch input grounded when it is not connected to a motherboard. Check your case switch, it is momentary.

Sense inputs measure the power supply voltage at the load and adjust the voltage so as to be within spec.

I would not be surprised to find similar connector with different pin outs on Compaq / HP or Dell systems. They want you to buy their over priced replacements.

ATX power supplies are electronically switched. They can and do false. This is why you should switch off or unplug the supply when adding or removing cards from the slots.

Reply to
Lord Garth

Ok. I'm confused here. The mobo has a standard ATX connector and expects stqandard inputs. The power supply is different and doesn't have a powerok line ( instead it has a fan on line in it's place ).

The funny behaviour I see is after I ( partially ) install the PS. It turns on the momment I connect the PS to a 120 outlet, not waiting for me to "push the button", which i find confusing.

I haven't kept the system on for very long, but in the time that it is on, it stays on.

So I guess that I should change the leads so that the connector matches up with the ATX spec with regards to sensing. The question is where do I put the grounded lead that is sensing. The ATX doesn't have anything like that in it.

You point here isn't clear to me. Everytime I connect the PS to a 120V source it powers up. So this isn't some kind of "false" startup.

The reply-to email address is snipped-for-privacy@yahoo.com. This is an address I ignore. To reply via email, remove 2002 and change yahoo to interaccess,

** Thaddeus L. Olczyk, PhD

There is a difference between

*thinking* you know something, and *knowing* you know something.
Reply to
TLOlczyk

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