> that blew.   The incoming line and the case I have the amp in are grounded 
> or so it seems to me.  Is there any way to protect the overall system or 
> should I consider board replacement an operating expense.

Dealing with lightning currents is just like dealing with noise in board
design, just bigger. You should have a lightning rod, grounded to its own
ground stakes (3 of them, a foot apart, 10 feet deep, minimum) and this
setup should be as far away from your instrumentation as possible. Then
be sure that the lowest resistance path from your vault ground, rack ground,
etc. to the same ground stakes is via a thick wire that's run as far 
away from your signal wires as possible. The input leads should be
twisted as tightly as possible to eliminate loop area for magnetic coupling
of the surge to the inputs of the gear. Finally you should look at the
input circuitry of whatever blew up and protect it with gas tubes and/or
MOV type surge suppressors, each routed to the same ground stake. Wide
copper strap from the earth stake to your cold water system is good too.



-- 
David Josephson / Josephson Engineering / San Jose CA / david@.............

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