[Hammarlund] SP-600 HFO Alignment

[Richard Knoppow]

    There is no adjustment on the SP-600 (or the RCA AR88 
either). Use the logging dial to note the exact frequency 
reading. When everything is right the spec for the SP-600 is 
0.25% but actually it should be better than that. The older Super 
Pro was speced at 0.5% but should be half that. There, of course 
one can correct the reading at specific points as one can with 
any receiver with a separate band spread.

On 3/24/2020 11:53 AM, Hy Chantz wrote:
> Hope all of you and yours are doing well during these challenging times.
>
> Question if I might...let's say one has access to an xtal calibrator for their SP-600, and/or a WWV or other off-the-air reference.
>
> Other than an out-of-cabinet tweaking, what - if anything - is the common "Vernier" to use, to get the SP-600 dial readout exactly "on"?
>
> I don't readily see how one can easily align/move the dial scribe, there does not seem to be any commonly-installed  front-panel capacitor/trimmer to do this, and of course the tried-and-true fine-tuning of a Bandset to perfectly align the Bandspread as performed with other Hammarlunds, Hallis, etc. can't be done.
>
> ( of course, an answer to the effect of "..the SP-600 has many strengths, dial readout is not chief among them..." is entirely satisfactory!)
>   
> Thanks and best 73s!
>
> Hy  W2HY
>
> ----- Original Message -----
> From: "Bill Cromwell" <wrcromwell at gmail.com>
> To: hammarlund at mailman.qth.net
> Sent: Tuesday, March 24, 2020 2:23:44 PM
> Subject: Re: [Hammarlund] SP-600 HFO Alignment
>
> Hi,
>
> I took some radio/tv classes for a while (once upon a time) and they
> taught bending the *outer* rotor plates to get tracking in the AA5 AM
> broadcast band receivers. I have seen radios with intentionally bent
> plates and there was no satisfaction there. Don't do it.
>
> 73,
>
> Bill  KU8H
>
> On 3/24/20 11:11 AM, k2cby at optonline.net wrote:
>> 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
>>
>>    
>>
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL