20 Jan
2012
20 Jan
'12
1:58 a.m.
From: Eric Smith
Sent: Wednesday, January 18, 2012 9:44 PM
Ian King wrote:
> Instead of all of that, why not just replace the capacitors?
Why not just verify that the capacitors meet
specifications, and only
replace them if they've failed?
Ian was not at LCM yet when we did exactly this, after reading the CDE
white paper. More than 95% of the aluminum electrolytic caps in the 2065
had failed. We first tried "re-forming" a few. They failed again in
days.
At that point we made the decision never to waste our time on this. We
buy new capacitors (or higher-level components; cf. our PDP-7) and put
them in.
> On our PDP-7, we elected not to replace the filter
capacitors, which
> are the size of large soup cans.
Have you looked at the capacitors in the
"capacitor box" of the ECL
power supply of the KL10, between the H760 raw supply and H761 regulated
supply? There are 13 300,000uF 15V capacitors. There are certainly
modern replacements that are smaller, but if they're not broken, I'm not
going to replace them. They're also fairly expensive, roughly $50 each.
As I noted above, Ian was not on the 2065 project. (He did the same kind
of surgery on our VAX-11/785 systems.) Keith and I did the 2065, with
the aid of two friends of yours, Bruce Kennard and Bob Sellars.
The point is that we *run* our systems, unlike the PDP-1 at CHM. We can't
afford to mess around.
Rich Alderson
Vintage Computing Sr. Systems Engineer
Vulcan, Inc.
505 5th Avenue S, Suite 900
Seattle, WA 98104
mailto:RichA at vulcan.com
mailto:RichA at LivingComputerMuseum.org
http://www.LivingComputerMuseum.org/