K7AAY wrote:

Suggestions on priorities for troubleshooting, by tube replacement or
otherwise, appreciated. I feel the detector is the place to start?
Have a multimeter, is all. In Portland (OR) Metro area.

Maybe, or something before the detector. You really, really want a scope.

If you don't have a scope, you can make the assumption that what has gone
bad is _probably_ a paper cap somewhere in the IF strip or detector, and
just shotgun all the paper caps out. If it turns out not to be a paper
cap, you haven't wasted your time because sooner or later one of them will
fail.

The second thing you can do is measure grid, plate, and cathode voltages
on each of the tubes on the IF strip and detector stage, and see if any of
them is way out of wack. If you see 200V on a grid, you have a DC blocking
cap issue. If you see 10V on a plate, you have a plate resistor gone open.
If you see 200V on a cathode, you have a cathode resistor gone open.

It's a lot easier with a scope and a signal generator because you can run
signal in and trace it step by step with the scope, so you can identify the
offending stage before you start poking around with the meter. This saves
a lot of time.

It's almost certainly not a tube. Tubes fail sometimes, but resistors and
capacitors fail more often. I would make sure all the filaments are lit
first, of course.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."