28 Apr
2002
28 Apr
'02
12:15 a.m.
These voltages are OK for an unloaded system. Put in four or five 2102
memory boards and it drops to 7.5 volts. If you want to replace that big
capacitor you can find a new replacement at Mouser Electronics.
www.mouser.com
The Mouser part number is 539-CGS16V110000 and they cost about $22. This is
the right size, 2.5 x 4.125 inches.
Michael Holley
www.swtpc.com/mholley
----- Original Message -----
From: "Louis Schulman" <louiss(a)gate.net>
To: <classiccmp(a)classiccmp.org>
Sent: Saturday, April 27, 2002 8:07 PM
Subject: Old Power Supplies, revisited
I am putting my SWTPc 6800 back together, after
complete disassembly
for cleaning. So, on to testing the power supply.
It works! But here's the question, which I know has been discussed
before with respect to S-100 machines.
The power supply is a big transformer with one really big (91,000 ufd)
capacitor, and the usual rectifier stuff, etc. The documents call for
7-8 volts unregulated, along with + and - 12V.
I am getting something like 9.3 V, and + and - 14.3 V. Are these
voltages too high? Of course, on the SS-50 and SS-30 cards there are
voltage regulators, but I don't want to cause any damage. This thing
probably hasn't been powered up in 25 years.
How can I check the capacitor function without an oscilloscope or other
fancy equipment? Should I worry about "reforming" the capacitor?
Thoughts appreciated.
Louis