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Re: Bad blocks

this is a classic hardware troubleshooting problem. you most likely
had dirty contacts. pulling the cables of and then pushing them back
on caused all the contacts to get wiped clean enough to work again. 

this is an extremely common problem, although it can be very very hard
to actually track down. that's why i evolved the three rules of
troubleshooting in the mid-70s:

1) check your power. make sure it's on everywhere it's supposed to be.

2) wiggle the tubes. (ok, this was back when there were still lots of
things made with vacuum tubes in them). the idea here is that
mechanical contacts get dirty, and even when you think they're
reasonably sealed against that--it ain't so. this means check ALL
mechanical contact connections, including cable plugs/sockets.

3) check your cables. it's entirely possible to have crimped
connections inside plugs and sockets break, and then they'll look
intermittent depending on temperature (or other factors that cause
cable flexing).

so when you have your yearly regularly scheduled maintenance, you
should pull off ALL the cables and put them back on, probably twice
for surety.

these little rules have worked for me many many times. and there have
been times when I've forgotten them and tried something else, only to
discover that they would have been the right solution anyway.

 -- clint

Clint Hyde		"Give me a LispM or give me death!" -- anonymous

Advanced Decision Systems	Internet:  chyde@chesapeake.ads.com
2111 Wilson Blvd #800
Arlington, VA 22201		(703) 875-0327