[R-390] R-390A BFO

[wabate]

Glad to report that I made a mountain out of a mole hill!  The slug had 
only separated from the tuning shaft.  Unfortunately you have to remove 
the rear bakelite disc to get at the slug.  After you unsolder the leads 
that attach to the disc you need to straighten the twisted ends of the 
metal supports.  Once that is done, just pull it off.  The slug fell 
out.  It appears to be epoxied to the tuning shaft.  Rather than clean 
off the old epoxy, I just reversed the slug and epoxied it in place. 
There is a hole that goes all the way through the slug that makes this easy.

Reverse the disassembly and calibrate the BFO per the manual.  Not that 
difficult at all. The hardest thing was pulling the can apart.  It was 
sealed with an O-ring which was stubborn.  Guess the PTO disassembly 
made me expect the worse.  Works great now!

73,

Bill, K3PGB
.
> ----- Original Message ----- From: "wabate" <wabate at verizon.net>
> To: "R-390" <R-390 at mailman.qth.net>
> Sent: Saturday, January 19, 2008 4:05 PM
> Subject: [R-390] R-390A BFO
> 
> 
>> Hi,
>>
>> Just finished the cosmetic restoration of another 390A.  Its looking 
>> pretty good.  Turned it on and was able to hear some stations without 
>> doing an electrical alignment.  I started to check the various 
>> functions when I found the BFO was not working right.  I could go from 
>> zero beat to a 3 KC pitch on the minus side but on the + side it would 
>> only go to about 1 KC.  I took the shaft off and spun the BFO shaft 
>> with my fingers and every revolution it would go low and then high 
>> repetitively.
>>
>> Finally figured out this had to be an inductance problem.  So I took 
>> the BFO apart.  Never saw the insides before.  Sure enough, it appears 
>> that the slug (or something) is against the pivot point at the end of 
>> the coil form and it wont retract.  If I turn the shaft 
>> counterclockwise I can see the bakelite disc support flex as the slug 
>> tries to move out. So I'm against the stop. When I turn the shaft 
>> clockwise, it just unscrews. So the slug is jammed or something.
>>
>> Are there any articles on BFO repair?  I don't remember any.  Anyone 
>> been down this road? I can't be the first.  Its difficult to 
>> understand what is going on mechanically as there are threads inside 
>> of threads. One is left hand and the other is right.  I don't want to 
>> destroy anything in my learning process if I can avoid it.  THis BFO 
>> was serviced by someone before as there are pliers marks on the 
>> outside collar. So someone has messed with this.  There may even be 
>> parts missing! AARRGGHHHH!!!!
>>
>> Thanks,
>>
>> Bill, K3PGB
>>
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