14 Sep
2010
14 Sep
'10
1:38 p.m.
Al,
Do you know which board/component inside the Alto creates 5V from
the incoming 15V? If you can describe it in detail, it will help me
immensely (so I can diagnose the failed component).
I beleive it's a circuit (more than one component is involved) inside the
Diablo drive. Certainly the Model 30s I used on a PDP11 only took +/-15V
from the PSU.
You need to get the service manual for the deive (Eric Smith suggested
there's something of use on bitsavers) and see how the 5V is produced.
Note that the fault may well not be in that section. It's entirely
possible for excessive loading (say a very leay capacitor) to pull the
output of the regualtor cirucit down so that it can't supply 5V properly.
Before you start replacing parts you, as ever, need to do some tests
(Yes, I know this is not the way it's done these days, but it's the way i
do it, and it's never failed me...)
-tony