[Hammarlund] Old Hammarlunds - the Geissler modifications.

[Kenneth G. Gordon]

On 14 Apr 2011 at 17:18, djed1 at aol.com wrote:

> ---Original Message-----
> The Geisler mod involves more than the first mixer- there are changes
> to the detector, RF and AVC also. 

I was re-reading that article this morning: Geissler modified BOTH RF stages 
to a cascode circuit using 6SL7s.

He modified the mixer also to a cascode circuit using a 6SL7. In fact, except 
for inputs, the circuit is identical with the 2 RF stages.

He modified the HFO to a 6SL7 triode oscillator and cathode follower.

He completely removed the 6N7, and modified the 6H6 to a combined 2nd 
detector and noise limiter.

He modifed the AGC circuitry, and reversed the wiring to the "S" meter.

Lastly, he modified the audio stages, changing the first tube from a triode-
connected pentode to a pentode, and changing the biasing on other stages 
to provide "...10 more watts of audio...", and "...better tone".

As far as I am concerned, his only mod that has any kind of merit at all is the 
change to the HFO, but even that could have been done better and less 
intrusively.

IMHO, the 6F6s run hot enough at 14 watts: they must have been red-hot at 
24 watts output. Ye gods!

And last, but not least, his documentation is incomplete.

Anyone who considers the Geissler mods to be "reasonable" is, IMHO, quite 
simply, nuts.

Ken W7EKB