Stuart Rohre wrote:
> You an check for gross shorts or opens with the diode test function on the
> finals too. I would imagine they might fail short rather than open. Do
> they get hot, even with low power output? That would be a short. Of
> course, if open, they might act as a capacitor and pass some driver power to
> the antenna connection.
I think the leads are accessible without taking the board out. Maybe a
bit of poking around, but definitely worth a try.
>
> Just be sure any meter you use has low current if acting as a ohm meter for
> testing. And voltage. Modern DMM's are probably safe for finals and
> drivers.
Yes, I only use a DMM these days.
>
> Might be reluctant to use an old AVO meter VOM to test in today's transistor
> circuits.
Years ago I had an ancient AVO but it probably went in a clear out.
They're worth a bit nowadays...
>
> A surely safe test for a final, is to check the source or emitter resistor
> DC voltage drop. If there is a voltage drop, it is handling some current.
> If no voltage at the resistor high side, the device is open.
> 73,
> -Stuart
> K5KVH
Just a thought.. When diodes blow, I presume they go open circuit. Or do
they? Is it possible just to destroy the semiconducting properties and
leave a linear resistor?
73
Bob
MM0RKT
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