[Hammarlund] BC-779s and mods (was HQ-129 serial number list)

[djed1 at aol.com]

I bought a BC-779 at Dayton, which had been modified but was cosmetically good.  I wanted to restore it to original condition, but it was substantially modified with dual triodes for all the RF tubes, missing the noise limiter, and sundry other wiring changes.  I spent a lot of time going through tube by tube rebuilding the circuit, until quite by chance I discovered an old copy of CQ (Dec 1957) which had an article by Leonard Geisler entitled "Souping the Super-Pro".  It was exactly the modifications done to my radio, and I was able to track and remove all of the modifications easily.  Since he changed the AVC and NL wiring, it would not have been easy to track down all the wiring changes.  At that time the mods included replacing all four RF tubes, but did not include moving the power supply to the main chassis.  It was still a time-consuming job, but a sentimental journey since the Super-Pro was my first real radio.  I converted my original radio to all solid state in order to solve the drift problem, but then abandoned it in the early 70s for the lure of a R-390A.  I still have that one.Once I got the BC-779 all rebuilt, it worked well for a pre-WW2 radio.  The warm-up drift is still daunting.  Even with a TC cap, it drifts 10s of KHz for the first few hours.  I also picked up an excellent SP-400 which only required recapping and a few minor repairs.  It took me a year to find the two small original tuning knobs. I definitely have a soft spot for old Super-Pros.
Ed  W2EMN

-----Original Message-----
From: Kenneth G. Gordon <kgordon2006 at frontier.com>
To: Ed Tanton <n4xy at comcast.net>
Cc: Hammarlund <Hammarlund at mailman.qth.net>
Sent: Mon, Mar 23, 2020 3:49 pm
Subject: Re: [Hammarlund] BC-779s and mods (was HQ-129 serial number list)

On 23 Mar 2020 at 14:09, Ed Tanton wrote:

> I would like a copy: n4xy at comcast.net
> 
> Ed Tanton
> Marietta, GA

OK, Ed and anyone else who needs them.

There are 5 separate PDF articles on these mods. Since I am not sure which mods have 
been attempted on your receivers, I will send them all. I suspect the one that is of most 
importance to you is the one labeled, Ultimate_Super_Pro. BTW that article was not written 
by Lee, but Reed in 1957 for CQ magazine and is 9 pages long.

Lee wrote one on adding/converting the Super-Pro for SSB, and Geissler wrote another 
article on modifying the Super-Pro.

Lee also wrote an article on modifying the AR-88 for "improved performance". I am not 
including that one.

Lastly, the service bulletin from Hammarlund (which I cannot find directly now, but will 
continue to look for it) is mentioned in detail in a Hints and Kinks. The capacitor suggested 
is a 3.3 pfd TC cap with as high a negative temperature coefficient as possible. N-750 will 
work, but an N-1500 was suggested by Hammarlund.

I will include all these PDFs to anyone who wishes to have them.

Ken W7EKB
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