[R-390] RF subchassis separation

Tue Mar 4 07:41:35 EST 2014

Could a hole be drilled in the RF coil asssy to allow the head of the screw to fit into it?

73,

Bill  
WA2DVU

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Chris
Sent: Monday, March 03, 2014 11:10 PM
To: r-390 at mailman.qth.net
Subject: Re: [R-390] RF subchassis separation

Well I just happened to think, and went to look at a crusty RF deck I have for parts.  That plate sits flush against the RF coil assembly chassis, so if a screw is used it must be countersunk and not sit above the surface of the plate.  I don't really want to separate mine at the moment, but perhaps someone with a gear train assy separated from the rest can chime in.  

Chris 

Sent from my outdated iPhone wireless thingy

On Mar 3, 2014, at 10:01 PM, Chris Farley <kc9ieq at yahoo.com> wrote:

> I was looking through the drawings to see how that shaft is supposed to be pressed/crimped into place.  It appears there may be a drawing missing from the set (SM-D-178900 missing, as referenced to on SM-B-178901), but here is info gleamed from drawings of the shaft, the RF gear train assembly front plate, and the gear train assembly:
> 
> The pressed-in portion of the shaft is .219" +.001" -.000" by .040" deep.  That end also has a hole drilled into it, which strangely is shown without specs, aside from being 1/4" deep and tapped at 8-32.  
> 
> The hole in that front plate is complicated.  .2187" +.0005" -.0000" hole.  Countersunk at 82° ±3° to .343" on the front, and countersunk at 82° ±3° to .248" on the rear. 
> 
> Now I'm no machinist, but that sure seems like it must be a temporary "hold it in place" plan given the approx .0001" press-fitand overlapping tolerances, and then probably flared out from the rear for a more solid fit.  
> Question is, why does the shaft drawing show the rear hole to be threaded??  Is there actually the possibility of using a screw to hold that shaft in place?  One is not shown on any of the drawings I have seen thus far.  
> BUT if it IS indeed threaded and they aren't messed up from whatever pressing or staking took place, or the ID is such that you COULD drill/tap it, sticking a truss head screw (or a screw with a <shudder> FLAT WASHER) in there would seemingly be a pretty easy fix, assuming there is clearance behind the plate. 
> 
> ????
> 
> Regards,
> Chris
> 
> 
> 
> 
> ________________________________
> From: rbethman <rbethman at comcast.net>
> To: r-390 at mailman.qth.net
> Sent: Monday, March 3, 2014 8:40 PM
> Subject: Re: [R-390] RF subchassis separation
> 
> 
> Mark,
> 
> I've looked at the post you showed in the pic.
> 
> Since it was highly likely a press fit, it can be "staked" to fix it 
> back in place.
> 
> It won't be a simple task.  I'd seek out someone with machinist skills.  
> That would be someone that can help with this.
> 
> Application of something very like the metal bonding tube that for the 
> life of me that I can't remember right now.
> 
> The combination of "staking" and that compound should make it tight 
> once more.
> 
> By golly!  I think it is JB Weld.  It finally popped into the old 
> noggin as I began to sign the end!
> 
> Regards,
> Bob - N0DGN
> 
> 
> 
> 
> On 3/3/2014 8:35 PM, Mark Richards wrote:
>> Now finally doing a rebuild of my R-390A.  Gear train has been 
>> disassembled, cleaned, and now in the re-assembly process I hit a
>> snag:  there's a post which hosts the Differential Gear Assembly, and 
>> it is very loose.  It cannot be screwed down tightly.  I suspect that 
>> this post is press-fit into the gear backing plate. As the post is 
>> loose, I think this is accounting for the fact that the Differential 
>> Gears are not aligning properly with adjacent gears, nor with the 
>> front gear cover.  There is considerable mechanical friction when the 
>> front plate is attached.
>> 
>> So, my questions:
>> 
>> 1. Can the RF Subchassis be separated from the gear assembly plate and...
>> 2. Can the Differential Gear Assembly post be repaired?
>> 
>> A photo of the offending post:
>> 
>>     http://kumichan.net/private/03-03-2014 20-28-04.png
>> 
>> 
>> I have another complete gear/RF Subchassis that is of dubious 
>> electrical condition, but is mechanically sound.  If I can separate 
>> gears from chassis, then maybe an option is to swap out the RF 
>> Subchassis with the good gear set?
>> 
>> 
>> /K1MGY
> 
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