13 Sep
2010
13 Sep
'10
1:26 p.m.
I thought a video might be easier for you all to see the issue I am
having with restoring my Xerox Alto.
The issue I am having is the Diablo Disk drive does not power on fully
(I am measuring +15 and -15V on the drive, but +5V is only measuring at
around 2.5V. The lamps on the front of the drive do not light-up, and
the LOAD/RUN button does nothing, hence the door lock does not unlock.
I don't know the Alto at all, but this sounds a bit like a Diablo model
30 drive. In it?
If so, from whta I remember, it derrives the +5V rail intenrally from the
+15V supply. If the +5V rail is low, then either there's a problem in the
regulator, or an overcurrnet condition (maybe a nearly-shorted
capacitor).
FWIW, I have the DIablo Model 30 service mnaual, but it woudl take a
little time to find it.
Here is a link to the video: http://www.youtube.com/watch?v=mx80CvjuvyE
I have visually inspected all PCB boards and components, nothing seem to
be damaged. Also, the power supplies seem to be outputting power
properly (as seen via the RED voltage LEDS in the Alto card cage.
I would still chekc thiem with a voltmeter and a 'scope (to look for
excessive ripple).
Any recommendations on how to troubleshoot the disk
drive further?
-tony