[R-390] R-390 Problem

[mikea]

On Wed, Feb 17, 2010 at 11:56:06AM -0600, Gary Harmon wrote:
> My Collins R-390 (non A) has a strange problem.  If the line voltage drop
> below 120 volts, the signal goes away but audio rush remains.  Kick the line
> voltage back up to 121 and the signals return.  The 180 volts does not
> change in either situation.  All tubes in the power supply and audio modules
> have been replaced with tested tubes.  Additionally, when you turn on the
> radio from a cold start, it take about a minute for the signals to apprear.
> 
> Thoughts anyone?

Oscillator(s) quitting when the voltage drops? Hinky 3TF7? Try shooting
the voltages out of the power supply to the PTO, for a start. I think.
Someone else may have a better idea; I won't be surprised. 

Does this happen on all bands, or just some? At both ends of the PTO
range and in the middle, or only in certain spots? 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin