[Hammarlund] B on SP-200 faceplate?

[Richard Knoppow]

----- Original Message ----- 
From: "Bill Cromwell" <wrcromwell at gmail.com>
To: "Gary" <xfrmrs at roadrunner.com>
Cc: <hammarlund at mailman.qth.net>
Sent: Wednesday, March 27, 2013 1:29 PM
Subject: Re: [Hammarlund] B on SP-200 faceplate?


> On Wed, 2013-03-27 at 16:13 -0400, Gary wrote:
>> BOATANCHOR?
>> >
>> >
>> > Does anyone know what the B stands for on the faceplate 
>> > of this SP-200?
>
>
> What about three or four of those in a row A, B, C, D, 
> etc.
>
> 73,
>
> Bill  KU8H

    It occurred to me after I posted that it might have been 
modified for diversity reception.  This _was_ done to some 
Super-Pro's. It involves bringing out the AVC and diode load 
to the rear panel and usually installation of a gain trimmer 
so that the two or three receivers can all have equal gain. 
That could be the extra knob.  However it would not explain 
the missing dial shutter or changed S-meter.  I rather agree 
with the person who suggested the receiver had been taken 
apart and not put together again very carefully.
    As far as modifications, my BC-779 was modified when I 
got it according to the articles by Geisler (?) in CQ 
magazine in the late 1940s.  Geisler changed all the RF 
stages to 6SL7 dual triodes using a common cathode 
arrangement.  I think he left the LO alone but can't 
remember.  Anyway, the set will still receive but the idea 
that it would have much lower noise, etc., is accompanied by 
vices which far outweigh the virtues.  Since my receiver had 
already been hacked I used it as a test bed for some 
experiments of my own but eventually restored it to original 
with the exception of a VR tube for the LO. BTW, my receiver 
had the scars of a fixed-frequency crystal oscillator on it 
similar to the arrangement used on the SP-600-JX.  it had 
been removed by left a couple of holes in the front panel 
above the main tuning dial and a hole in the cover for the 
main tuning side of the turret.  All patched.  When properly 
restored these are very fine receivers with good 
selectivity, especially the crystal filter, and excellent 
rejection of images and spurs. They do need voltage 
regulation of the LO otherwise they will shift frequency 
with the RF gain.  The also have a lot of warm up drift but 
evidently Hammarlund added a single temperature compensating 
cap to the LO in the last of the SP-400 series.  Its shown 
in the schematics but no value is given, evidently they were 
selected at the factory.
     I need to get my BC-779 out of storage and work it 
over. I did not at the time replace the paper caps which 
have by now probably all turned into resistors.


--
Richard Knoppow
Los Angeles
WB6KBL
dickburk at ix.netcom.com