[Hammarlund] Old Hammarlunds

[Jim Wilhite]

>From what I know about the process, after construction, they would track 
the drift for a given period of time, usually 15-30 minutes, then add 
the necessary TC caps to the circuit to correct for the drift. 
Receivers of the same model and design could have different TC caps 
added depending on what that drift was.  Many times there would be a 
footnote at the TC cap on the schematic and in the footnotes would be a 
note saying "value determined at final construction" or some such.

I am sure they finalized a couple or three values of TC caps in the 
design phase and had them on hand for the final test area.  It is 
amazing when you find a receiver that has not been abused to see just 
how stable they can be.  Today there isn't that many TC caps to be 
bought, Z5U, etc.

Recently I came across a parts box full of the old values and have it in 
my stash.  I am certain that if I need a particular value, I won't have 
it but will have hundreds of them that won't work in the circuit

Jim/W5JO



> ----- Original Message ----- 

>    It would be interesting to know especially if the
> compensation was detailed in any schematics or even in parts
> lists. That would be a very good clue for adding it to older
> receivers. I doubt if H would have changed the tuning caps
> but the value of the fixed padders and trimmers might have
> been changed.
>
>



>
>
>> Also realize that the one cap across the variable is there
>> for all bands.
>> That means other values may be needed for the lower ranges
>> that have to be
>> wired into the oscillator circuits.
>>
>> Later production SP-400's had TC but I dont have that
>> detail handy at the
>> moment.
>>
>> Carl
>>