Collins 32S-1 help
 

I have a 32S-1 that has been sitting for about 30 years, turned on
occasionally in hopes of keeping the capacitors happy but never set
to actually transmit. The PA plate current was a bit high (perhaps
70ma) so I adjusted the bias; maybe this was a mistake. When I
tried to tune it up there was no signal.

The BFO, VFO, and HF crystal oscillators were on frequency and most
of the voltages I checked seemed reasonable. The tone oscillator,
however, was not... oscillating. The tube (V11B) appeared to be
conducting, pulling down the plate voltage. I tried a different
tube still in the socket extender and it worked; however, it did not
work with the extender removed. I suspect the cathode bypass capacitor
(C6B). I put the extender back for the time being.

With the tone oscillator oscillating the exciter tuning was giving me
a nice response on the PA grid current and I was getting 100W into
a dummy load. Unfortunately I got a little carried away and probably
spent too much time tweaking the response. There was a blue flash
and the line fuse opened. With the fuse replaced I still get output
but the PA grid current is weird. It may go negative or it may go off
the scale (seemingly randomly) when I switch to tune. It doesn't seem
to depend strongly on the exciter tuning. I'm thinking I overheated
one or both of the PA tubes and some element warped and shorted.

If nothing is obvious on visual inspection of the PA tubes would it be
reasonable to try with one at a time removed?

Dan Lanciani
ddl@danlan.*com

Collins 32S-1 help
 

"Dan Lanciani" ddl@danlan.*com wrote in message
...
I have a 32S-1 that has been sitting for about 30 years, turned on
occasionally in hopes of keeping the capacitors happy but never set
to actually transmit. The PA plate current was a bit high (perhaps
70ma) so I adjusted the bias; maybe this was a mistake. When I
tried to tune it up there was no signal.

The BFO, VFO, and HF crystal oscillators were on frequency and most
of the voltages I checked seemed reasonable. The tone oscillator,
however, was not... oscillating. The tube (V11B) appeared to be
conducting, pulling down the plate voltage. I tried a different
tube still in the socket extender and it worked; however, it did not
work with the extender removed. I suspect the cathode bypass capacitor
(C6B). I put the extender back for the time being.

With the tone oscillator oscillating the exciter tuning was giving me
a nice response on the PA grid current and I was getting 100W into
a dummy load. Unfortunately I got a little carried away and probably
spent too much time tweaking the response. There was a blue flash
and the line fuse opened. With the fuse replaced I still get output
but the PA grid current is weird. It may go negative or it may go off
the scale (seemingly randomly) when I switch to tune. It doesn't seem
to depend strongly on the exciter tuning. I'm thinking I overheated
one or both of the PA tubes and some element warped and shorted.

If nothing is obvious on visual inspection of the PA tubes would it be
reasonable to try with one at a time removed?

Dan Lanciani
ddl@danlan.*com
Dan,
The first thing to do is go through and tighten all the screws on the
chassis. Many ground connections rely on the screws and lockwashers for
their integrity.
73, Bob AD3K