[R-390] Solid State Ballast 'quirks'?

[Mikek]

Howdy

I have a Collins 390a that has a solid state ballast
replacement that I got as part of the restoration.
Sometimes, while listening, the station will suddenly
'go away' and just have static.  I noticed some of what
appears to be 60 cycle hum in the audio.  The Tuning and
BFO does nil but the AF section is still working and selecting
the various filters has the noticeable 'audio' so I wonder
if the 'balast' cut off.  I power off the radio and let it
sit and sometimes the set comes back for a while then goes
dead.  Other times, I let the radio sit overnight and the
next day all is good - SO, I know this is an intermittent - should
I zero in on the solid state ballast first - I suspected that
unit since the only thing that seems to go away is the tuning/bfo
- any one seen this before??  Any other places to look while
troubleshooting?

Thanks es 73
Mike AA9IL
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