@Oldsmobile_Mike
Sure, but first take not that messing around with PC power supplies could fry your computer or worse yet, yourself!
For the record, I really reccomend getting a decent tower conversion rather than what I am about to describe for a desktop machine.
Even My A1200T is still rigged this way internally (using 2 power feeds, I mean) supplying power from the cases PSU to the motherboard in 2 places.
Back to the 1200D
Like many of my friends, I had an old PC kicking around with a spare 200W AT PSU. First and foremost, the PSU needs to be in working order. A duff one could ruin your machine at the flick of a switch.
Next check that the main power switch is either
1) Physically mounted into the PSU itself (ususally round the back of the PC).
Or
2) Is on the end of a cable (ie the power switch is mounted in the front of the PC's case somewhere) but explitly connects only the low voltage DC side!
Whatever you do, don't go playing with any PSU that uses a power switch on the end of a cable that carries mains voltages. You could get electrocuted!
Such PSUs are fairly rare but I have seen a few them. The power switch connectors ususally have heavy insulation on the lugs.
If you are in any doubt, you are probably best of leaving the PSU in the PC case.
There are aminet files explaining how to connect an A1200 power cable to the PC's PSU. I wont go into detail here (principally because I can't remember the basic amiga power cable pin out and don't want to give you ill advice), but basically you need to source +5V, +12V, 0V and -12V on the PSU for the 1200 power cable.
-12V is the only one not part of any ot the normal PSU disk power connectors. You will find it on the main PC mobo power connector - it's usually colour coded blue, but check thouroughly on the PSU's legend.
Assuming you have your basic 1200 power cable connected up you now have plenty of juice available.
So far, all this has been the normal stuff to get a beefier PSU.
In order to prevent current damage to my 1200 mobo (as happened to my friend) I decided to add a secondary rail to my 1200D as I explained earlier.
I took a spare 1200 power cable and chopped the connector off the end and the old brick off the other. I then used this cable to simply extend one of the PC PSU's drive power connectors (just the 0/+5/+12VDC) such that it would reach my amiga.
I fitted the male version of the same connector to the hard drive / floppy drive power cable inside my 1200 and mounted it on the back of my amiga case.
This basically meant that the hard drive and floppy drive were now powered directly from the PSU and not via the amiga motherboard anymore, thus reducing the current flow through it.
Eventually I took this one step further and used the motherboard floppy power connector to feed 0/+5V/+12V into the motherboard via a standard floppy power connector. Even without powering the drives, the 040 card still drew some current.
The pin configuration for the 1200 mobo floppy power connector is +5V, 0V, 0V, +12V from left to right, looking at the motherboard as it would be normally inside it's case (and in front of you).
I still use this configuration in my 1200T, using a spare floppy power connector to feed the motherboard there and also via the original power cable.
