AT Power Supply Connectors

[Kevin Webb]

My brother has an old AT PC that has been doing a fine job in his business
chugging away for several years. He recently noticed it was getting hot and
gave me a call. The PSU was very hot because the fan had stopped working. I
couldn't find a new AT PSU anywhere but found a used one in the PC graveyard
that is my loft.
When I went to replace the PSU in my brother's PC I found 2 problemettes.
1. The switch in the old unit was a rocker switch with four spade connectors
to the PSU. The replacment had a soldered on push switch with only two wires
to the PSU. the two sitches are not physically interchangeable. I intend to
check that the push switch is push on/push off rather than a momentary
device then use a couple of crimp spade females to connect the replacement
PC to the old switch. Any problems you can forsee?
2. The motherboard connectors are very similar and labelled P8 and P9 on
both PSUs. The plastic upstand next to the male connectors on the
motherboard has a number of slots in it. These line up with small nibs on
the old PSU plugs. But with the replacement plugs, the P9 lines up OK but
the nib is positioned differently on the P8 connector. Any idea what this is
all about? Both PSU's are labelled with the voltages for each wire colour
and they are the same (one doesn't mention the orange) and the wires are in
the same positions. I can snip off a nib and they will both fit fine.

Your help would be greatly appreciated.

K.

[Chris Hill]

On Fri, 29 Oct 2004 01:46:54 +0100, "Kevin Webb"
<kevin.webb-removetoreply-@ntlworld.com> wrote:
My brother has an old AT PC that has been doing a fine job in his businesschugging away for several years. He recently noticed it was getting hot andgave me a call. The PSU was very hot because the fan had stopped working. Icouldn't find a new AT PSU anywhere but found a used one in the PC graveyardthat is my loft.When I went to replace the PSU in my brother's PC I found 2 problemettes.1. The switch in the old unit was a rocker switch with four spade connectorsto the PSU. The replacment had a soldered on push switch with only two wiresto the PSU. the two sitches are not physically interchangeable. I intend tocheck that the push switch is push on/push off rather than a momentarydevice then use a couple of crimp spade females to connect the replacementPC to the old switch. Any problems you can forsee?2. The motherboard connectors are very similar and labelled P8 and P9 onboth PSUs. The plastic upstand next to the male connectors on themotherboard has a number of slots in it. These line up with small nibs onthe old PSU plugs. But with the replacement plugs, the P9 lines up OK butthe nib is positioned differently on the P8 connector. Any idea what this isall about? Both PSU's are labelled with the voltages for each wire colourand they are the same (one doesn't mention the orange) and the wires are inthe same positions. I can snip off a nib and they will both fit fine.


Wouldn't it be simpler just to replace the fan? I think you could be
getting yourself in a heap of trouble since the wires aren't exactly
the same here.

[Kevin Webb]

"Chris Hill" <hillco@earthlink.net> wrote in message
news:4ud4o0l75eqeeev9336pola3uk32qg26du@4ax.com... On Fri, 29 Oct 2004 01:46:54 +0100, "Kevin Webb" <kevin.webb-removetoreply-@ntlworld.com> wrote:My brother has an old AT PC that has been doing a fine job in his
businesschugging away for several years. He recently noticed it was getting hot
andgave me a call. The PSU was very hot because the fan had stopped working.
Icouldn't find a new AT PSU anywhere but found a used one in the PC
graveyardthat is my loft.When I went to replace the PSU in my brother's PC I found 2 problemettes.1. The switch in the old unit was a rocker switch with four spade
connectorsto the PSU. The replacment had a soldered on push switch with only two
wiresto the PSU. the two sitches are not physically interchangeable. I intend
tocheck that the push switch is push on/push off rather than a momentarydevice then use a couple of crimp spade females to connect the
replacementPC to the old switch. Any problems you can forsee?2. The motherboard connectors are very similar and labelled P8 and P9 onboth PSUs. The plastic upstand next to the male connectors on themotherboard has a number of slots in it. These line up with small nibs onthe old PSU plugs. But with the replacement plugs, the P9 lines up OK butthe nib is positioned differently on the P8 connector. Any idea what this
isall about? Both PSU's are labelled with the voltages for each wire colourand they are the same (one doesn't mention the orange) and the wires are
inthe same positions. I can snip off a nib and they will both fit fine. Wouldn't it be simpler just to replace the fan? I think you could be getting yourself in a heap of trouble since the wires aren't exactly the same here.

Thanks, Chris.
I had only a very few minutes to look at the computer before the pub closed
so my thoughts were fogged by other considerations. I changed the fan in an
Enermax PSU recently. There was next to no space in the box and and it used
tiny connectors for the fan, much smaller than standard fan connectors,
fiddly little devils, that experience has put me off replacing PSU fans;
though I expect these old AT PSUs would be easier. Also I couldn't tell
whether the fans would be the same depth and whether the replacement would
fit; again probably not actually a problem. Then I thought the old PSU was
half fried anyway and I wondered whether it was actually the fan that was at
fault; but as the PC was still working the rest of the PSU was probably
still OK. Then there was that cool clear pint of lager waiting at the pub...
I actually switched the PSUs, cut off the nib and left the replacement psu
switch dangling out of a drive bay. It seems to work OK and now doesn't seem
to be in iminent danger of catching fire.
I do need to tidy up the job though, and I don't remember coming across
differences in AT motherboard connectors, so I'd still really be interested
in anything anyone knows about the reason for the nibs on the connectors, or
what different standards exist for AT power switches. I've Googled about but
couldn't find any references on the net.

[Chris Hill]

On Fri, 29 Oct 2004 19:03:37 +0100, "Kevin Webb"
I do need to tidy up the job though, and I don't remember coming acrossdifferences in AT motherboard connectors, so I'd still really be interestedin anything anyone knows about the reason for the nibs on the connectors, orwhat different standards exist for AT power switches. I've Googled about butcouldn't find any references on the net.


I suspect it has something to do with the power good line.

[Charles Howse]

Previously Chris Hill <hillco@earthlink.net> wrote: On Fri, 29 Oct 2004 19:03:37 +0100, "Kevin Webb"
I do need to tidy up the job though, and I don't remember coming acrossdifferences in AT motherboard connectors, so I'd still really be interestedin anything anyone knows about the reason for the nibs on the connectors, orwhat different standards exist for AT power switches. I've Googled about butcouldn't find any references on the net.
The thing is there are no standards fro AT power switches. There are
some "Vendor standards". In those times the PSU usually came with
the case and it was not so important.

I think the first real standard came with ATX, where the standard moves
the power-switch to the mainboard and a low-voltage 2-pin push-button
is the solution for user-driven power switch acivity. This made
things like Wake-on-Lan, Wake-on-Modem, etc. possible and also
allowes for general compatibility between ATX PSUs.

One comment on the connectors: These are perhaps the worst designed
connectors I have ever seen: Usually you can swap the two halves,
resulting in Mainboard/PSU explosion if you are unlucky.

Arno
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