Help Needed on R390A

[Doug]

Hi Dave.....sounds like you've been given a dandy rig.  I used to
repair the 390/390A series for the Navy's Security Group, so
I'll try to be of help.  I think we had 300 of 'em to keep us busy.

The band switch is driven by a cam system that locks the RF tuning
coil racks with the HF oscillator, and tunes the IF's.  To access the
wafers themselves, remove the RF deck by releasing the green headed
screws and the power plug (turn the lock ring to turn it loose).  Gently
remove the deck and turn it over....underneath are the actual switches
and wiring.  Clean those well with some contact cleaner/lube.

Most tuning troubles with these rigs are due to poor mechanical
alignment, resulting in things being out of sync and not tuning properly.
So...take a look at the cams on the front and back of the RF/IF unit.

First off, tune the indicator to 7000+00, take a good look inside at
the front of the RF assembly, find the index marks on the cams.  Each
one should be aligned with it's cooresponding mark on the front plate
of the assembly.  If not, you'll need an alignment tool....just a spline
wrench brazed into the end of a 10 or 12 inch piece of tubing and
fitted with a handle or some such equivalent.  Now, loosen the gear
clamps and align the marks on All of the cams....retightening the
clamps just snug, not real tight so you dont break the clamps.  Now,
firmly push down on the coil racks to see if any of them move down.
If not, you're in good shape.  If they move, ya might have a busted
clamp, which are available from Fair Radio Supply for a few bux.
When you finish....all the cams and gears should rotate smoothly,
and have NO binds or crunching sounds coming from the mechanism
or dial.  You can use a LITTLE light oil on the cam surfaces, but keep it
off of the shafts in the gear clamp areas.  Lube there will require the
clamps to be set tighter than they should and therefore bust 'em.

I see you've tested the bottles, so you're off and running now.  You
can pick up a maintenance from Fair Radio.....I think they're $25 or
so, but worth the money.

You'll need to do RF/IF alignment according to the chart in the book,
but if you need info, write me and I'll try to get all of it together for
you.  A good quality sig gen is really necessary, along with a VOM
to monitor the AGC voltage and the Diode Load strap on the back
of the rcvr.

As far as price goes, I'd say it'd be worth $300-400 as is, assuming
it's all complete.  I picked one up a while back minus meters for parts
at $300 plus shipping.  But, since yours has meters and covers, it'd go
for a bit more.  A really cherry R390A would be worth $500-600,
plus shipping.

Most R390S's were used in racks, requiring the covers to be pulled
to allow better cooling.  So, the covers are scarce.  Fortunately, both
of mine have covers.  Since the little buggers are a touch on the heavy
side, most Matmen were pretty big guys.....they kept 'em around just
to install and pull the 390's!  They could be a turkey to change out.

Good luck and email me if I can be of any help to your project.

73

Doug, K7YD
Livingston, MT


Dave Hollander wrote:

> I was recently given a Collins R-390A  - yes given (I lost a ton of stuff
> to my ex-wife last year so this was well deserved). It has both top and
> bottom covers and both meters which I have come to find out is a big deal!
>
> Having not owned one, I have paid any attention to other messages on the
> R390A but now have a few questions myself.
>
> After replacing 4 tubes, the unit came to life, however it is dead on
> several bands - 2, 6, 10 Mhz and intermittant on .1-1 Mhz. After studying
> the insides, it is not intuitively obvious on how to get at the band
> switch to clean it with de-ox. I also do not have the manual yet. Being
> it looks like a mechanical nightmare to me, can anyone explain how to get
> at the bandswitch? Also do the bands that are dead share a common xtal by
> any chance?
>
> Also what is this puppy worth? Panel has wear on screw holes where it
> would mount to a rack. Main tuning knob is missing paint, rest of panel
> and knobs look pretty clean, about an 8.5 and it does have meters and
> covers!
>
> Any help is appreciated
>
> 73,
>
> Dave Hollander N7RK
>
> ***************************************************************************
> ***
>
> Dave  N7RK -  Webmaster CADXA
> Phoenix, Arizona         *DXCC Honor Roll*    *WAZ#23 - 75 Meter SSB*
>
>                  ex-N7RK/ZB2, VK2ERK, ZM0AJN, WB6NRK
>
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