I've got a Centurion also and dug out the book. It seems what you are
describing is S-1, the INTERLOCK switch on the HV-AC board (81536), not
to be confused with S-1 on the front panel, the main power switch.
This board contains 3 relays which switch the ac line voltage to the
plate xfmr primaries and the fan. Upon operating the front panel switch,
a 12 vdc supply on the QSK board comes alive, sends 12 vdc to connector
2 on the HV-AC board, goes thru your (vaporized) s-1 interlock and turns
on relays 1 and 3. Relay k-2 is operated via a 1 sec time delay from
Q-1, also on the HV-AC board.
It seems to me the only things that could cause excess current to flow
thru the interlock is:
C4, a .01 uf bypass on the collector of Q-1 going short or Q-1 itself
going short. (Well, OK, one of the relay coils could go short, but
that's extremely unlikely).
Check Q-1 or C-4 on the HV-AC board, take 2 aspirins and call me in the
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