[Hammarlund] SP-600 HFO Alignment

[k2cby at optonline.net]

I would repeat in boldface underlined Never bend the plates of the tuning
capacitor! It is undoable and a death sentence so far as proper alignment is
concerned.

That said, there are several points to consider in trying to match the HFO
frequency to the tuning dial.

1.	On the frequencies below 7.4 MHz (the 3 lower bands) be sure that
the IF is actually centered at 455 kHz, and on the higher bands be sure that
the IF is aligned at 3,955 kHz and the crystal oscillator is putting out
3,500.00 kHz.
2.	Be sure there isn't some non-factory "improvement" hanging off the
wire that runs from the plastic feed-through at the front of the RF strip to
the VFO-Crystal oscillator switch. That wire leads directly to the HF
oscillator, and any stray capacitance to ground will foul up the frequency
calibration at the high end.
3.	Without touching the oscillator coils, use the proper size steel
screwdriver to "exercise" the air variable capacitors of the oscillator
section for each band. Especially if the boat anchor has been sitting
untouched for a couple of decades, the capacitor shafts will stiffen and you
will either bend or break a plastic alignment tool.

 

Miles B. Anderson, K2CBY
16 Round Pond Lane
Sag Harbor, New York 11963-3821
Phone: (631) 725-4400
FAX: (631) 725-2223

e-mail: k2cby at optimum.net