[Hallicrafters] Mixer alignment problem

[Gerry Steffens]

I have come across a problem a number of times over the many years.  It
appears to be a problem on the lower price tiers of radios.  I have observed
it in Hallicrafters S-38E, S-120, S-108 (and maybe on S-85) radios among
others.

When doing an alignment, usually on the high frequency band only but I think
I have seen it on the third band occasionally, having completed oscillator
alignment successfully, I have found that when peaking the mixer section on
the high end of the band, the oscillator appears to be pulled by the
adjustment of the mixer trimmer causing detuning or incorrect calibration of
the band.

I have never pursued this problem further before but have kind of taken on
the challenge this time.  So far no real successes.  I suspect some stray
coupling somewhere but where or what?

Any ideas would be appreciated and anyone else experienced this problem?

Thanks & Cheers from Minnesota, 

Gerry


Collecting & Restoring E.H. Scott, 
McMurdo Silver, Hallicrafters, Zenith 
Transoceanic and any other interesting 
radios since the 1960s

Gerald Steffens P.E.
Oronoco, MN


Over 300 "Boatanchors" salvaged.
Collection approaching 300 radios, 2 Oldsmobiles and a 1950 GMC.