[Hammarlund] Old Hammarlunds - modifications.

[djed1 at aol.com]

---Original Message-----

 The Geisler mod involves more than the first mixer- there are changes to the detector, RF and AVC also.  The BC-779 I bought had the 6SL7s in it, so I got a good price on it. When I opened it up, not only was the mixer and RF stage modified, but the detector wiring was unrecognizable and the noise limiter 6N7 was completely gone.  After about a week of scratching my head trying to undo all this, I had resorted to buzzing out each wire on the schematic.  While I was taking a break from this dreary task, I thumbed through a stack of old QSTs stored next to the workbench.  And there it was!  A CQ magazine with "Souping the Super Pro".  Once I had the article, it was easy to track down and reverse all the changes.  It would have been interesting to see what the performance of the Geisler mods were, but I was too far along in the restoration at that time.
Ed  W2EMN




From: Todd, KA1KAQ <ka1kaq at gmail.com>
To: kgordon2006 <kgordon2006 at frontier.com>
Cc: Hammarlund <Hammarlund at mailman.qth.net>
Sent: Thu, Apr 14, 2011 12:53 pm
Subject: Re: [Hammarlund] Old Hammarlunds - modifications.


On Thu, Apr 14, 2011 at 12:00 PM, Kenneth G. Gordon

<kgordon2006 at frontier.com> wrote:

> A kind soul on this list sent me zipped copies of three articles from CQ

> magazine detailing modifications to the Super Pro. These are the Geissler

> article from 1957, the Lee article from 1958, and the Reed article from 1961.

>

> ALL of these are rather extensive, and NONE of them seem to me to be

> totally necessary.





I think the time in which these articles appear indicate more about

the mods than anything. Back then, not many hams had a choice of the

plethora of gear we have today and instead had to make do with

whatever would fit their budget. There were a lot of surplus Super

Pros kicking around along with the BC-348, Command set/ARC-5s, and so

on. Wasn't around until the newest article was published, so I can't

say for sure but my guess would be that you did whatever you could to

upgrade/improve whatever you already had or could afford to buy.



Referring back to Henry Rogers' page on the Super Pros under

'Modification Mayhem', a number of these modifications seem to address

problems that were related more to user issues than actual design

deficiencies, or desires to somehow make a late 1930s radio into a

newer set:



"L. E. Geisler Modifications - With the cheap, easy to find

availability of the surplus WWII Super-Pro receivers in the

mid-fifties and sixties, the "modification mania" did finally catch up

with the line and the WWII Super-Pro was considered "fair game" for

modifications. Most of the infamous Super-Pro modifications were

derived from the first of the series, "Souping the Super Pro" by L.E.

Geisler, published in the Dec.1957 issue of CQ magazine. Geisler was

an engineer that worked out of Japan for a company that sold modified

Super-Pro receivers. Today, Geisler's modifications are "tame" and

basically replace the 6L7 mixer tube with a different octal mixer tube

that is quieter, then he replaces all of the capacitors and does a

full alignment - pretty much standard stuff. Geisler's mods are

conservative, make sense, improve performance and do no real harm to

the receiver. One has to remember that Geisler's company sold these

modified Super-Pro receivers so they had to perform better yet still

retain the professional-commercial appearance in order to have

marketability.



Post-Geisler Modifications - The later modification articles

endeavored to "out-do" Geisler's "makes sense" conservative approach

with more and more outrageous modifications. Included in the list of

notorious "cut and hack" articles are "A Super 'Super-Pro'" and

"SSBing the Super Pro" - both published in the "Surplus Conversion

Handbook," part of the CQ Technical Series. These articles advocate

the wholesale modification (destruction) of the entire receiver,

including replacement of the front-end tubes with miniature tubes, an

on-board solid-state power supply, removal of the 14 watt P-P audio

section to install an anemic 6AQ5 single ended audio section (which

also then provided room for the on-board power supply,) on-board

converters to cover 10 and 15 meters, product and infinite impedance

detectors - on and on. It's doubtful that a receiver could ever be

returned to original after being the victim of these later

modifications. I have only seen a couple of Super-Pros that attempted

these modifications and they were wrecks. No doubt, the end product

failed to impress the owners and the receivers were afterward

relegated to the junk pile."





While it probably made sense at the time, in today's world with so

many 'better' options(if that's one one seeks) available with new

sets, it seems like a lesson in futility. But since there are already

so many hacked up versions out there, we have plenty of opportunity to

investigate that side, too.



I sold one of these sets years ago that had every octal replaced with

miniature tubes. It looked like an empty box. A fellow in MA has

converted one to all solid state devices. It looks even worse! I

currently have two pre-war SX models which have both been hacked to

some extent. I'm hoping to restore at least one of them back to all

octal tubes, replace the other bad components, and go from there.

Unfortunately, it's never easy to figure out someone else's ideas

involved, especially when they never completed the mess!



The ones with the onboard power supply and hacked out audio are

horrendous. I always remind myself that it was someone else's radio

and I can't appreciate why they did it since I wasn't there. I try to

respect the role that surplus gear and amateur mods played in our

hobby decades ago, it's just that some of them seem to make so little

sense for the work involved.



~ Todd,  KA1KAQ/4

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