Using a PC Power Supply On The Beeb
By Crispin Boylan (E4W)
On December 19th 1997, for the first time since I owned my old Torch C-500
computer which sadly has now stopped working, I became the proud owner of
a Dual Drive BBC Model B, and what a relief it is to have two drives in
use at the same time, copying becomes a joy when it was once a nightmare,
and playing games like Elite or doing word processing means that saving
files is no longer a chore, but something of a necessity. My dual drives
were kindly given to me by Ian Bell, someone who I owe a lot to for his
constant help every time I have phoned him, thanks Ian! Anyway, it was
actually the case which he gave to me, and also the ribbon and power
cables, as I already had 3 Mitsubishi Disk Drives, albeit bare with no
cases, but they are very reliable, 80t double sided drives, stepping up
from my old Akhter 40t Double sided very nicely!
Anyway, we had agreed to send the disk drives to me, and then, when I had
phoned Ian asking about help with the View word processor which I had just
obtained, he told me that he was very sorry, but the dual drive case which
he had in mind to send me was powered from the Beeb, and there was no self
powered PSU - "Never mind," I said, thinking that it would be perfectly
fine to connect it to the Beeb, if they made it like that, it must work, I
thought. Well, after receiving it, putting the drives in and making sure
that the whole thing was fine, I eagerly plugged it in to the Beeb's
auxillary power supply socket, and then the data cable, turn on the Beeb
and everything was fine!
Or was it? I soon noticed that the Power Supply was running extremely
hot, and with the APTL board that I had also purchased, which was drawing
some power, I thought that my old PSU might break down in tears if it got
any hotter! So, my attentions turned to figuring out a way to get a power
supply, looking through the Beeb Body Building website on the PC (yes, I
do have a pc as well, although I don't use it for word processing or
anything else much, because my Dad needs it for his work) I found that
there was an article on making a power supply for your disk drives, but
alas, when I tried to view it, it was not available! The only one not
available, would you believe it?
Well, further e-mails to Chris Richardson, asking about whether I could
get his article from him or not, revealed that he had none, he did however
tell me that he had used a dual drive powered from the beeb quite happily
for years, and he had really given it some welly! He also suggested using
another BBC power supply to just power the drives, which I could buy from
him for £10, not a bad price! Anyway, after carefully thinking it all
over, I decided to try and go for an even bigger power supply, one from,
yes, that most power hungry of beasts, the PC!!
Finding a power supply was easy, £20 for a 120w one, or like the one I
got, from a shop which was throwing old pc's out, nothing for a 60w power
supply! I was told that this could happily power 3 drives and one hard
disk, so 2 5 1/4 inch drives should be a cinch for this thing! It already
has the connectors for 3 5 1/4 inch drives,or hard disks, and 2 for 3 1/2
drives, so no problems there! It also had a load of floating leads, which
were connected to the motherboard of the PC, and were very useful for
connecting extra devices such as powered 2nd Processors, interface boards,
and anything else requiring a power supply of 12v, 5v, -12v, -5v, common
in most things.
So next time you think that you are running low on plugs, or that its just
too messy with all those power cables, pick up a dirt cheap power supply
from a PC, plug in all your floppy drives, and find out what voltages the
other peripherals need, fit a terminating block to the power supply and
feed in any spare wires, then strip back the wires on the peripheral, and
plug them in to the corresponding voltage wires on the terminal block!
Then you have several devices running from one plug socket, you can quite
happily run anything you want from the Power Supply, as long as you don't
overload it!!
Try it out, make part of a PC actually do real work for once!