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Subject: Re: Need another Fix it Kit
From: Martin Tom Brown
Reply To: mapug@shore.net
Date: Fri May 03 01:09:19 1996

In message <960502183607_388938295@emout15.mail.aol.com> DBaker1047@aol.com writes:

> Meade. I had the scope mounted in an Observatory with the transformer
> plugged in all the time. The on-off switch was controlled at the scope.

A dodgy on-off switch might be the common cause.

> Just a thought......everyone talks about the voltage jumps and spikes and
> burnouts etc..... what then, are the two fuses for in the system. There is
> one at the transformer lead line prior to entering the power input of the
> scope and then there is one on the back of the circuit board on the scope
> base. I have had neither of these fuses blow prior to experiencing these
> electrical problems. I would have thought that that was what they were there
> for....to protect the internal circuitry. Apparently mine failed to
> safeguard my electronics.

It's a corollary of Murphy's Law.

A penny fuse protects itself by allowing expensive electronics to fry.

Seriously the fuse can only help if there is a high current fault
persisting for one or two seconds (enough to melt the fuse wire).
Like a stalled motor or electrical short circuit. It is surprising
just how long a fuse will last at say 200% rated current.

The fuses are useful - just limited protection for semiconductors.

Regards,

-- 
Martin Brown  <martin@nezumi.demon.co.uk>     __                CIS: 71651,470
Scientific Software Consultancy             /^,,)__/