19 Jul
2005
19 Jul
'05
1:13 p.m.
On Tue, 19 Jul 2005, cswiger wrote:
I understand. They must have run the 49,000 tubes
pretty
conservatively to minimize failures (Unlike what we always
hear about ENIAC). Even in 1976 my Heathkit VTVM got
solid state plug in FET replacements for the two tubes ;)
Preventive maintenance played a huge part in the reliability of the
system. The Q7 had a marginal checking system, which was used to test
sections of the computer by slightly increasing or decreasing voltages to
the modules. By running diagnostics with margins, we usually got a heads
up on which tubes were about to fail, and could replace them before they
actually failed in use.
Mike Loewen mloewen at cpumagic.scol.pa.us
Old Technology http://ripsaw.cac.psu.edu/~mloewen/Oldtech/