[SignalOne] CX7A Back Together

[jerry]

The PA cage is reassembled.  Wow, what a PITA of a job!  I note that 
Signal/One sold the bandswitch with coils as a single spare part.

   Put the radio all back together.
   After a no-receive hiccup ( forgot to hook up a wire ) I got good 
receive again.

But no transmit.  Dead as a coffin nail.  Before, I at least had 50W or 
so on 40M.

Went back to troubleshooting.  I had seen signal entering the RF driver 
board, but none coming out.  Specifically,
the CA3028A at the input of the RF board.

Hmm - there's this input at the CA3028A called "ALC".  It's biased at 
about midpoint between ground and the +15 supply rail.  I swear it was 
midpoint before.

Anyway, now it's zero volts.  Something is shorting it to ground.  I 
pulled the wire off the ALC input and *poof*, we have RF!

Only not as much as before.  17W out on 40M.  S'OK, THAT I can work 
with.

The BAD thing is on 20M.  The PA tuning *arcs*.  Zap! And on 80M!  Zap!  
And on 40M!  Zap!

I see there is mention of parasitic oscillations in the Trouble Guide.  
"Place a single ferrite bead at the 8072
socket on the grid and screen terminals."   I'm honestly surprised that 
there is no facility for neutralization.

                   - Jerry, KF6VB