Jul - The R-390A Frequently Asked Questions Page

leave that phase alone. Left the gears in the RF deck and scrubbed them down with a long bristle
brush, a toothbrush and carburator cleaner. Got probably 70% of the old grease out, rinsed the carb
cleaner out and followed that with a scrubbing with 50/50 Simple Green and water solution then a
thorough rinse with hot water. Blew out the gear train with compressed air and let it sit in the 100
degree heat we had one day. Once dry, I re-lubricated everything, of course.
Pulled each slug rack out and dipped the bearing in the carb cleaner and gave them a twist. Cleaned
everything but the actual slug with a toothbrush then submerged the bearing ends a final time and
moved them. Gunk came out and the bearings on the racks move nicely now. Lubed the bearings and
faces of the racks with 90W oil and placed them back in the radio. No wholesale replacement of
capacitors in the IF deck but noted there are certainly plenty of them. I imagine they could give you a
fit if one started leaking.
Anyone out there in List Land have information on which ones commonly fail in this radio? Other
common problems that I ought to chase down before they become serious issues?
Found the 1st RF tube replaced with a 6AK5 v/s a 6AJ5 as are all the oscillator tubes. Also, there is a
6BH6 as the last IF amp. I wonder if these are helpful mods AKA: W3HM and the 75A-4 mods or did
someone popped some tubes and just stuck those in 'cause they fit?
Repainted and re-lettered the front panel. Stripped and painted the knobs, cleaned all the sub-chassis,
set the PTO length, balanced the upper and lower band end over-run and set up the mechanical
alignment for the cams. Tied it all together by setting up the Cam Position/PTO length/electrical
relationships, centered the Antenna Trimmer and then did a full IF and RF alignment.
To put it bluntly, the radios performance is impressive. I did not do a full sensitivity test but knew it
was very hot. For some reason, I had it tuned to 15.400 and heard Radio Kuwait with no antenna
connected other than the shielded BNC cable going to the HP-8640B generator. I did a spot check at
the 3.8 mhz RF deck alignment point and was floored.
Ben Wallace and Mike Harris (just finished his) are currently tied for "most sensitive R390A's I have
yet to restore." This one beats both by a hair but, keep in mind, its a different radio. Much higher build
quality in the non "A" but I am not sure there are performance differences between the non "A" and the
"A" that would justify what must have been the cost difference.
I'd like to find out the various problem caps and maybe pre-emptively replace them. Also, the filter
caps seem to be either papers a-la the 32V-3 HV cap or are oil filled's. They could also probably stand
to be replaced, again on a pre- emptive basis.
This does not make me an R390 expert and I have no plans at present to start restoring them. Having
no real parts stock and little direct experience makes that idea one who's time has not yet come.
However, its a start. -73- Chuck Rippel, WA4HHG
From Barry Hauser" I restored my Collins R390 over the long weekend. I had it traded to me on a > "it
worked the last time I tried it" basis. Basically, that means it was broken > and the "seller" pretty much
knew it.
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