silent workstation

the silent workstation idea is just a way to recycle an old 486SuX-33
as a network terminal ,its fast enough for text editing and web browsing
with Linux mini distro but it will be in a room that I
want quiet so I've pulled the hard drive and the only fan is in the PS
its a Compaq with proprietary power connectors on the motherboard
so it would take some minor testing and surgery to swap supplies
the PS fan runs off the 12v rail and if disconnected the unit will not work
at all (normally this would be ok) the power requirements are minimal
with no hard drives to keep spinning and only a network card on an
'all in one' motherboard it would just have to run the floppy drive for
a few minutes at bootup and run from ram the rest of the time

for heatsinking the PS I was thinking to just add bigger sinks to any
component that already had one ,I do know better than to fiddle with these
things under power(I'm crazy but not THAT crazy)
always make sure to discharge the caps with a power resistor first

I've tried the same idea before using a 386 and an old Apple PSU but
it never made it thru the BIOS POST , a regulated bench supply did
work but the transformer humm was louder than a regular fan
I tried using a working AT supply with a dead fan as well but wouldn't
ya know it the fan came back to life as soon as I bought a new supply
to replace it

Update - it works

I've managed to hack the original Compaq power supply for silent running
here are some of the details
the original fan was a Nidec 12v .15a brushless fan and was connected
to +12v and a +5v health monitor circuit as "ground" return (it was already
fairly
quiet but had some bearing rattle) the health monitor wire showed +5v with
sharp
spikes to ground when the fan was running and the supply would shut down if
the fan stopped spinning so I had to replace the fan load with a simulated fan
load

snip snip and out comes the fan in its place goes a small (~1/2" dia)toroidal
transformer (1:1) ripped from an old modem
with series diodes (1N4004 or 1N4004) 1 in and 1 out of the primary winding
on the secondary winding I put 2 more diodes out to a 68ohm 2w resistor then
2 more series diodes back in to the secondary winding
don't ask me why but it works :-)

the modified supply is re-mounted more or less vertically in the case to get
a little
bit of a chimney effect and during testing it did not need any additional
heatsinking
the sides and top of the case and supply did not get noticeably warmer than
a standard
box with fans in place and it has not gone into thermal shutdown after
several weeks of running 24/7 once the screen blanks you forget its on

silent workstation specs are
Compaq Presario 486SX-33 with 12mb ram
2S,1P, ps/2 mouse&kbd ,hard&floppy drive controlers and svga on motherboard
1ea 1.44mb floppy for boot only
1ea ethernet card
operating system CCLinux-1.5 available at
ftp://ftp.linux.tucows.com/pub/distributions/mini/CCLinux