18 Sep
1998
18 Sep
'98
5:31 p.m.
At 10:16 PM 9/18/98 -0700, it was written:
At 10:19 PM 9/18/98 -0500, Wirehead wrote:
On some (static memory and other) cards the linear regulators get quite hot
with the high input voltages. Doesn't help here that the 117 Volts is
sometimes 122 Volts or higher. For these systems I run them with a 12V
transformer wired as a 120 to 108V step down (buck) autotransformer. I first
tried with a variac to see how low the voltage can go, usually below 100V
with supplies with a lot of "margin", such as many of those open frame
linear supplies.
A note in defence of the much maligned Altair while on this subject...
May I point out the the Altair 'B' series machines were one of the first to
provide a main transformer with a multi-tap primary to allow for adjusting
for varying loads and local AC supply.
-jim
---
jimw(a)agora.rdrop.com
The Computer Garage - http://www.rdrop.com/~jimw
Computer Garage Fax - (503) 646-0174
I measured the voltages across a power connector
and got 9.4V, +17.56 and
-17.86. A little high but I attribute that to a lack of a load.
Actually, I think most power supplies in S100 mainframes tend to run a
bit high so they can handle the load and because it doesn't matter since
each board has it's own regulators anyway.
Anthony Clifton - Wirehead