Shugart 851 power problem

From: Bill Sudbrink <bill_at_chipware.com>
Date: Tue Apr 25 14:19:50 2000

Hi,

I have a pair of 851s in a nice case with power supply.
They are attached to a Cromemco 16FDC in an IMSAI box
with a Cromemco ZPU and an Expandoram 64K board. I'm
using the ROM enable on the 16FDC to drive the phantom
line. There is a reason for these details...

Here is the problem:

#1 Power up the drives by themselves:
At the drives:
  5 volt line reads 4.9
 -5 volt line reads -4.9
 24 volt line reads 23.9

#2 Power up the IMSAI box:
At the drives:
  5 volt line reads 1.2
 -5 volt line reads -0.9
 24 volt line reads 2.6
and (needless to say) the drives don't work. The Cromemco
ROM monitor gives all sorts of errors trying to access them.

#3 Power off the IMSAI box:
(Same as #1)

#4 Power on the IMSAI box again:
At the drives:
  5 volt line reads 5.0
 -5 volt line reads -5.0
 24 volt line reads 24.0
and the drives work fine.

What gives? Does this make sense to anybody out there?
Received on Tue Apr 25 2000 - 14:19:50 BST