[ARC5] BC-459 Drift

[Mark K3MSB]

This weekend I drove my SCR-274N for a vintage operating event.

I am experiencing some nasty intermittent drift problems with my BC-459-A,
and it seems to be getting worse.

When I restored the unit, I did general cleaning, replaced the bathtub
capacitor, and re-soldered all the joints I could get to.  I still had some
chirp which I wasn’t too concerned about, and drift was minimal.  This
weekend it got to the point that I decided to pull the 459 off the air (and
since 80M was dead, brought my operating fun to an end……).

I’m running my BC-456 to the 2 TX rack, but I was not running the
Dynamotor;   rather I just inserted the output of my HV PS onto the
appropriate BC-456 dynamotor pins.  I’ve done this before with no
problems.  Operation of the BC-696-A was great this weekend, and at times
the 459 was good too (a bit of chirp, but I’m not concerned about that
right now).

I did notice that when the drift and tone quality went bad, slightly moving
the tuning knob to a slightly different position would usually clear up the
problem for a short while.   This tells me there may be a problem with one
or both of the variable caps in the unit.  Thinking back, I don’t think I
could reach one of the solder connections on one of the caps, but I got the
other OK.  So I will concentrate in this area this week.

While I’m in there, are there any other things I should look for that I
haven’t already mentioned?

I was thinking of regulating the Oscillator voltage with a VR tube, but
based upon my observations, I doubt this is the issue.

All in all I still had a ball with the ARC-5s!  It’s really amazing what
they can do.  I picked up 3 more states for my ARC-5 WAS effort – only 12
more to go!

73 Mark K3MSB