[R-390] starting 390A restoration

[djed1 at aol.com]

 Good advice on replacing the black/brown beauties, but don't rely too much on the PTO article.  The linearity adjustment on the Collins/Motorola is substantially different than on the Cosmos.  My advice is to leave the linearity alone- adjust the endpoint and take a turn off if needed, but I don't recommend trying to adjust the corrector stack.  It usually is pretty good after you get the endpoint correct.
I've recapped mine, but I chickened out on disassembling the gear train.  I just flushed it with cleaner and relubed.  But mine wasn't real dirty to start with.
Ed  W2EMN

 

 

-----Original Message-----
From: nryan <nryan at mchsi.com>
To: Bob Young <bobyoung53 at hotmail.com>
Cc: r-390 <r-390 at mailman.qth.net>
Sent: Sat, Dec 1, 2012 2:40 pm
Subject: Re: [R-390] starting 390A restoration


Hi, Bob,

You're referring to the IF deck, not the RF deck, right?  The IF deck contains 
the "death cap."

You should replace any brown or black plastic-encased tubular caps, but keep the 
metal-encased ones except the "death cap."  That cap should be a high quality 
orange drop rated at 600VDC.

Replace out of spec resistors to optimize the unit and thus gain peace of mind.  
I use original carbon comp type resistors.

Here's a link to helpful photos of a geartrain teardown from a fellow (I think) 
r-390 list member:
http://militaryradio.com/R390A/R390RFDeck/

Your PTO make is Motorola, but this link to a Cosmos PTO rebuild may be helpful:
http://r-390.com/cosmos.htm

Good luck,
Norman

Any activity becomes creative when the doer cares about doing it right, or doing 
it better. -- John Updike


----- Original Message -----
From: Bob Young <bobyoung53 at hotmail.com>
To: r-390 at mailman.qth.net
Sent: Sat, 1 Dec 2012 12:42:50 -0600 (CST)
Subject: [R-390] starting 390A restoration


I have a Motorola R-390A I bought some years ago and have finally decided to 
start to restore it. It will be my first 390A rebuild. Everything worked last 
time I powered it up but it needs mucho maintenance. I plan on taking apart the 
gear train, lube it adjust it etc with the help of the Y2K manual (which looks 
really well done by the way), also see if the PTO (Motorola) can be brought back 
to within specs without taking a turn off (doubt it, it's more than 10 Kc off 
end to end), recap it, align it and do anything else that needs to be done. I am 
reading (and reading) the R-390A Frequently Asked Questions Page but am sure 
I'll have a lot of questions. The first is I pulled the RF deck today to see if 
it had the death cap still in it and it does. I also noticed three or four brown 
beauties in there, probably a stupid question but should I replace those also? 
Resistor checks also? Thanks,

Bob Young
KB1OKL
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