[R-390] Zero adjust on R-390 receiver

[Bob Camp]

Hi

Even light oil will turn into varnish after some number of years. Given the way these radios got (mis-) lubed by various generations over the years - who knows what's in / on the plates or the rest of the assembly. Dust / airborne crud / bits of stray trash are also a source of trouble.  Disassembly / cleaning / visual inspection is often the only way to be sure you have all the guck out of something like this. 

The clutch is only designed to go just so far. Past that point you likely are trying to compensate for something that's out of tolerance. First suspect would be the crystals…

Bob

On Mar 16, 2013, at 3:21 PM, n4buq <n4buq at knology.net> wrote:

> That's the way my  Motorola clutch worked (or, more correctly, didn't work).
> 
> A couple of things to check.  Are all the screws in the front panel?  If not, it could be allowing the panel to bow more than it should.  Second, is the clutch plate (the disc that's on the end of the front panel screw thingee) solid and made like it should be?  My Motorola had a rather home-made looking device which I replaced (it still didn't work like it should, though).
> 
> Could be that there is dried lube between the clutch plates.  I don't think they're supposed to be lubricated with any kind of "wet" lube" like oil, etc. (maybe, if anything, a dry lube like talc(?)).  If so, the plates could just be sticking together with grease/oil.
> 
> I seem to recall Roger having some thoughts on this way back when I worked on mine.  Maybe he'll chime in.
> 
> Barry - N4BUQ
> 
> On 3/16/2013 2:07 PM, Bob Young wrote:
>> Is there an adjustment in there? Mine needs about a half a turn to separate the surfaces but it gets difficult to turn once it gets to the point where the surfaces start to separate, these is some drag also and I have to turn it back and forth a few times to get it to stop turning the whole mechanism. I have it adjusted so it can't go in more than half a turn, if I turn it in anymore than that I feel like I'm forcing it and it creates drag (bending something?) when tuning from about 400 to approx 300 but only when tuning down,
>> 
>> Bob
>> KB1OKL
>> 
>> 
>>> Date: Sat, 16 Mar 2013 14:40:24 -0400
>>> From: rbethman at comcast.net
>>> To: r-390 at mailman.qth.net
>>> Subject: Re: [R-390] Zero adjust on R-390 receiver
>>> 
>>> You shouldn't need to drop the front panel to adjust it.
>>> 
>>> Turn the radio upside down.  You the have access to the assembly.
>>> 
>>> Bob - N0DGN
>>> 
>>> On 3/16/2013 2:34 PM, Bob Young wrote:
>>>> Mine has never worked correctly either, it takes a lot of effort to separate the clutch and it mating surface, it does work but with effort. It is probably adjusted incorrectly and I haven't had the time to drop the front panel to check it out and see what the problem is.
>>>> 
>>>> Bob
>>>> KB1OKL
>>  		 	   		
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> 
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