[R-390] Zero Adjust Clutch Repair

Tue Mar 19 10:00:09 EDT 2013

If I recall this correctly, each clutch disk (or every other disk?) has alternating sets of round and slightly elongated holes (I don't recall exactly but that's the gist of it).  I assume the elongated holes are to eliminate any mismatch between the center of the hole and the center of those little pins.

It has been several years, but as I recall, those disks can be installed in various configurations and I assume there is a right way and a wrong way to assemble them.  I seem to remember alternating the round holes and elongated holes as I stacked the discs.  That may or may not have made any difference, but if the pins are sticking like you report, it could be the discs have been stacked improperly.

While it isn't a picnic, it really isn't all that difficult to tear the clutch down, clean it, and reassemble it; however, as it turned out for my first R390A, it didn't really help (it did on the second one, though).  YMMV.

Regards,
Barry - N4BUQ

----- Original Message -----
> From: "Bob Young" <bobyoung53 at hotmail.com>
> To: r-390 at mailman.qth.net
> Sent: Tuesday, March 19, 2013 8:16:16 AM
> Subject: Re: [R-390] Zero Adjust Clutch Repair
> 
> I don't know about Howard's but on mine the clutch will pull away
> from it's mating surface a little bit but not uniformly, in other
> words one side of the clutch pulls away more than the other. I've
> put a thin screwdriver between the clutch while it's partially open
> and the other surface and it won't open any more overall, the clutch
> will pull away more where I put the screwdriver in but the opposite
> side then closes correspondingly if that makes any sense. When the
> Zero adjust touches the three little rods it will only move them in
> a little bit then one side or other binds and it becomes very
> difficult to turn it in any more, it does open enough though that
> after a few back and forth turns of the Kc change knob it will work
> and I can zero it. I'll try the WD-40 again with the small
> screwdriver. I did squirt some WD-40 in there a while ago but there
> was no difference, I did not try opening them with the screwdriver
> though,
>  
> Bob
> KB1OKL
>   
> 
> > Date: Mon, 18 Mar 2013 15:50:07 +0000
> > From: chuck.rippel at cox.net
> > To: r-390 at mailman.qth.net
> > Subject: [R-390] Zero Adjust Clutch Repair
> > 
> > In reading the thread, I haven't really gotten my mind around
> > exactly
> > what is broken/not working with the clutch.
> > 
> > Generally, I find that at one time, the clutch was oiled and that
> > oil
> > had hardened. You can turn the "ZERO ADJUST" knob all the way in
> > but
> > the clutch plates do not disengage and no adjustment can be made.
> > Is
> > that what we're talking about ?
> > 
> > If so, 80% of the time I find that the radio can be put on its
> > side, the
> > "ZERO ADJUST" cranked in and a few generous squirts of WD-40
> > sprayed
> > into the gaps in the clutch plates. Sometimes, a very small
> > screwdriver
> > needs to be worked in between the plates to open a gap. Once that's
> > done, with the Zero Adjust still fully engaged, rock the KC Change
> > knob
> > back and forth and try to break the clutch loose. Once its loose,
> > give
> > the plates another shot of WD40 while rocking the KC Change knob
> > back
> > and forth. The idea is to soften and flush out some of the hardened
> > lubricant.
> > 
> > If not, the clutch can be taken apart but its no picnic. There is a
> > "C"
> > clip that needs removed then the clutch discs, springs and plates
> > need
> > to be individually cleaned. Do NOT oil them !! Getting it back
> > together is also a chore.
> > 
> > --
> > No trees were killed to deliver this message. However, a large
> > number
> > of electrons were terribly inconvenienced.
> > 
> > Chuck Rippel
> > 
> > 
> > 
> > >
> > > Message: 2
> > > Date: Sat, 16 Mar 2013 16:38:49 -0400
> > > From: Bob Young <bobyoung53 at hotmail.com>
> > > To: "r-390 at mailman.qth.net" <r-390 at mailman.qth.net>
> > > Subject: Re: [R-390] Zero adjust on R-390 receiver
> > > Message-ID: <SNT136-W3953A23CBE155668D2BCD5CCEE0 at phx.gbl>
> > > Content-Type: text/plain; charset="Windows-1252"
> > >
> > > OK I have it upside down on the floor and one side of the clutch
> > > goes
> > > in farther than the other side, something is binding it or or it
> > > appears that way. Hard to tell with the front plate on. If I put
> > > a
> > > very thin screwdriver in there that part of the clutch will open
> > > more
> > > but then the other side binds against the mating surface. I think
> > > I'm
> > > goping to have to take it apart to really see what's going on.
> > > The
> > > three little rods seem to be ok and not binding.
> > >
> > > Bob
> > > KB1OKL
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