[Info-vax] Looking for a source for replace or repair some power supplies

[glen herrmannsfeldt]

Bill Gunshannon <billg999 at cs.uofs.edu> wrote:

(snip)
>> Yeah, David Turner was telling me about how to do that, if I could find 
>> an old power supply that provided -5 volt.

> Do ATX or the older PC PSU's provide it?  I have a number of old PC
> PSU's floating around here.

They should at least supply -12V, needed for RS232, and a single
regulator IC will get you -5V from that. In all cases I know,
the current is very low.

In the 8080 days, -5V was used for substrate bias, which keeps the
current from going between the transistors on the IC. 

The 8085 and Z80 went to 5V only, with an internal bias generator,
if needed.

What uses -5V on newer systems?

-- glen