[R-390] RF subchassis separation

[Chris Farley]

To answer the disassembly question-  

First off NO do NOT attempt to remove the cams/shafts.  If you look at the rear (and middle) ones, they are pinned in place.  Tearing these apart would be a mini-nightmare to straighten back out.  

That entire gear train assembly comes out as a unit-  Look at the picture from this completed eBay listing-  This whole thing comes out as one piece:

http://www.ebay.com/itm/COLLINS-R-390A-please-verify-GEAR-TRAIN-W-MILITARY-INSPECTION-TAG-/141203550647?pt=US_Ham_Radio_Transceivers&hash=item20e06331b7&nma=true&si=6mEUC20wSuT0ZP3Z55xr8VjD5Gk%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Now before you go "holy crap!", It's not as daunting as it looks.  

First if you haven't already, remove the slug racks and springs.  Remove the gear from the bandswitch shaft, and slide the shaft rearward enough so that the retaining clip may be removed.  Then remove the bandswitch shaft by pulling out through the front.  Pull it out straight, don't turn it and misalign the wafers.  The antenna trim control shaft and 2 screws holding that bracket must also be removed.  Now it gets easy.  From the rear, remove the 3 screws holding the back plate to the chassis.  Remove the two downward facing screws from the two brackets holding the center plate down, right behind the RF coils.  There are nuts and washers under the chassis on these two screws.  Then turning the unit upside down, remove the three hex head screws holding the front plate to the chassis with a 1/4" wrench.  That entire assembly as seen in the link should now be free and lift straight up from the chassis.  

It's possible I forgot a screw or step somewhere, but if you're mechanically inclined it's not hard to figure out.  I had mine separated in under a half hour, and that was the first time doing so.  

Good luck

Regards, 
Chris




________________________________
 From: Mark Richards <mark.richards at massmicro.com>
To: r-390 at mailman.qth.net 
Sent: Tuesday, March 4, 2014 7:03 AM
Subject: Re: [R-390] RF subchassis separation
 

To Chris, Bill, Barry, Norm, Roy, Bob... thank you!  I am overwhelmed 
with the number of replies and excellent thoughts.

In summary, the shaft is held in place with a countersunk screw 
(possibly philips head?) screw.  It is possible to gain access by 
separating the chassis.  Question is: how?  It appears removal of the 
cam assembly (as a start) is required, and this seems a frightening 
proposition.  Chris, can you give us some hints on how you got these apart?

Tried to tighten the shaft by rotating.. even with some pulling tension 
to friction-lock the screw, allowing the threads to take. No joy.  My 
guess is that whatever corrosion or chemical bond exists has formed with 
the shaft in the loose position.

/mark

K1MGY

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