Date   : Thu, 24 Oct 2002 12:01:51 +1300 (NZDT)
From   : Michael Foot <mjfoot@...>
Subject: Re: BBC motherboard from a PC power supply

Quoting Richard Gellman <r.gellman@...>:

> 
> >I have a spare Model B motherboard and keyboard and would like to know
> if
> anyone has had any experience with fitting the motherboard into a PC
> case
> and
> >using a PC power supply to power it? Is there any info on the web
> about
> this?
> 
> Its possible, but has to be done in a certain way.

OK. So far so good.

> 
> IIRC, the BBC Micro requires 4 isolated supplies, 3 of +5v + 0v, and
> one
> of -5v (this is a purple wire in my Model B).
> The -5v line and at least one 5v/0v pair can be obtained from the main
> power
> connector of the PSU. The other two you might have to gain from the
> drive
> power connectors.

Is it not possible to have all 3 sets of 5v/0v leads coming from the main 
power connector? ie. connect 3 wires to the 5v output and 3 wires to the 0v 
output.

> There's certain enough power in an AT PSU to drive a Model B at any
> rate.

More than enough I'd imagine - depending on the wattage of the PSU. I've got a 
number of PC 5.25 drives that can read BBC disc so I'll use those too.

> Failing all that, you can always build an isolation grid with 1:1
> isolator
> transformers.....

Um, probably way beyond my technical skills...

The other consideration is the keyboard. I'm thinking I might put it in a 
custom box and make up a long lead to run to the AT box. How long can I have 
this cable before it becomes unreliable?

Thanks.

Mike.

---
Michael Foot <mjfoot(at)paradise(dot)net(dot)nz> *
http://homepages.paradise.net.nz/mjfoot/
* Replace letters between () with @ and . when replying
---