Amiga 3000D psu: Is the -5V REALLY necessary???

[mingle]

Hi,

I'm looking at replacing the dead PSU in my newly arrived A3000D with a Micro ATX unit, but it seems that the original A3000 supply has a -5V line and not many later ATX supplies have -5V (it was deleted from the spec after ATX v1.1).

Looking at all the info (pretty much zilch!) seems to suggest that the -5V is only needed for certain old ISA cards, so I'm thinking that it's not really needed for 99.99% of Amiga 3000s...

So, can anyone confirm this? Does anyone have full A3000D schematics they could look at and see if indeed the -5V only goes to the ISA slots?

It'd make finding a replacement supply so much easier!

Cheers,

Mike.

[Zac67]

Audio and serial run off -12V, -5V isn't used on the mainboard at all as far as I can see. But apart from ISA it also goes to the video slot, so there might be a small chance you'd need it.

[Castellen]

The -5V is only required for certain expansion cards, though I've never seen any cards that use it.  The A3000 will run fine without it, the entire machine runs on +5V only.

+12V and -12V are required for the op-amps in the analogue audio stage and RS232 level shifters.

Connect +VID (pin 1 on the socket) to +5V.  Unless the ATX power supply delivers the 50Hz tick signal, you'll need to move J350 to position 2-3 to source this signal from the on board generated VSYNC signal.

[countzero]

sometime ago I did a picoPSU mod for my A3000. I can confirm that A3000 runs fine without -5v. But another user reported problem using the picasso 2 graphics board (on EAB), I wonder if Picasso 2 needs -5v ? My system has only a X-Surf as Zorro board and no problems so far ...

[Zac67]

Oh well, if you do require -5V (or want to make dead sure) why not regulate it with a simple 7905 from -12V?