Power interlocks (was Re: [OT] Alphaserver Oops!)

From: Eric Smith <eric_at_brouhaha.com>
Date: Tue Nov 10 20:07:13 1998

> Seems there's a power interlock in the top cover!

Jeffrey l Kaneko <jeff.kaneko_at_juno.com> wrote:
> I always jumper or otherwise disable those %&$_at_# things--
> they always cause more problems than they solve.

They certainly don't *ALWAYS* cause more problems than they solve.
Some interlocks are very important. For example, some of the interlocks
on vacuum column tape drives are to keep the tape from winding up in a tangle
all over the room (and in an extreme case possibly strangling someone).

Some computers can actually be damaged by operation with interlocks disabled.
For instance, one site disabled the door interlocks on a VAX 8600 while trying
to repair it. This led to the thermal sensors shutting it down. So they
disabled those too. It'll be OK for only a few minutes, right? No, they had
to replace about $15K worth of boards that failed due to overheating. All
because someone thought they knew better than the system designers and could
debug a problem on the cheap instead of calling in a qualified field service
engineer.

I'd suggest defeating interlocks only if you are *sure* you know what
you're doing, not if you *think* you know. In the case of the Alphaserver
that was cited in the earlier email, it is clear that the person opening the
machine did NOT know what was inside it, and it would have been entirely
inappropriate to defeat the interlock.

Eric
Received on Tue Nov 10 1998 - 20:07:13 GMT