Vax hardware problems

[utzoo!decvax!ucbvax!unix-wizards]

>From hill at SRC-UNIX Thu Nov 12 01:49:34 1981
	We have had a VAX 11/780 for about a year and have been
intermittently plagued with hardware problems.  The most troublesome
of these problems have been a flakey writeable control store and
bad power supplies.  We suffered about a month of 20 minute mean up
times due to the power supply problem.  Fortunately, we have a
reasonably capable maintenance crew here who diagnosed the problem
within a week, but it took us three weeks of threats and coercion
to get DEC to fix it.  As it turned out some DEC wizard out in
Colorado managed to find that the system was going through power
fail procedures when it was telling us about bad stacks and double
faults.  We had DEC scope the power supplies and convinced ourselves
that they were too spikey for a stable system.  DEC's response was
that they were switching power supplies and therefore spikes were
normal.  
	The power supplies have been replaced and we have had no
problem since (about two months).  Incidently, the writeable control
store problem caused strange error messages also.  Typically, they
were machine checks during fortran program execution.
	Hope this helps.
Alan R. Hill