[Hammarlund] B on SP-200 faceplate?

[Kenneth G. Gordon]

On 27 Mar 2013 at 14:29, Richard Knoppow wrote:

>     It occurred to me after I posted that it might have been 
> modified for diversity reception.

There is an added terminal strip on the right-rear (as you face the back) that 
appears to be just that.

>     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.

I also have one of those "Souped Up" Super Pros: the one in which the 
entire audio amp system was ripped out and replaced with a power supply, 
among other things. I keep it to eventually examine more closely to see if any 
of those "wonderful" mods actually made it work better. Somehow, I doubt it.

> 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.

I don't suppose you would be so kind as to list some of those vices?

> When properly 
> restored these are very fine receivers with good 
> selectivity, especially the crystal filter, and excellent 
> rejection of images and spurs.

Yes. At the time, they were the most expensive receivers available.

> 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 have seen a Hammarlund bulletin detailing this addition: it was a 3 pfd 
N-750. Supposedly, that reduces warm-up drift very, very noticeably.

>      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.

Indeed!!!!!

I have two other BC-779s: one is completely stock and unmolested...other 
than missing the dust cover, but it does include the stock power supply. 

The third one is probably only good for parts. It was given to me and is really 
ratty...but we will see once I get into it.

Many years ago, I was given a brand-new BC-779 with power supply by 
MARS. Although it worked OK, the BFO injection was absolutely abysmal 
and it hardly worked on CW, let alone SSB.

I got so frustrated with it that I changed the 6N7 noise limiter stage to a triode 
product-detector, the circuit for which I stole directly from the Heathkit 
SB-101 (which circuit Heathkit, apparently, stole from Collins).

As I have mentioned several times in the past 20 years or so, "WOW! What 
a major difference!!!!"

That receiver became one of my favorite receivers.

Ken W7EKB