Re: {Collins} 75A4 Band Change Dial Issue



Hi Alan,

Is the drum dial the original or is it a replacement overlay?
Some replacement overlays were not exactly the same as the original.  Additionally, if the old dial was left in place, it could increase the drum's diameter slightly making the problem worse.

That all said,  you can loosen the two Bristol grub screws on the right end of the drum. Then using a scale close to the center of the drum (like 20 meters), re-center in the escutcheon's window.
Adjusting the drum at the center of its rotation will minimize the error.
The Bristol set screws if never loosened before may require heating.  A thin soldering pencil inserted into the set screw socket for a minute or two will loosen the gyptol holding the screws.
The Bristol wrench you need is .069 four flute like the Xcelite 99-63.

Good luck,

Joe - KB9R


On 5/26/2019 10:45 AM, Alan Swinger via Collins wrote:
Just acquired a 75A4 from an SK Ham estate for which I am helping the family sell the station items. The A4 is clean, hears well and all functions appear to operate as designed. The only issue is mechanical in that Drum for the frequency spread gets out of synch when the band switch is rotated through full range. . . i.e. if aligned properly on 160 to start, freq spread lines migrate upward with each band change until at 10M the freq range is slightly above the viewing window. The set screws on the drum(right  side) appear tight and observe no slippage on the shaft when the band sw rotates Drum. My guess is a problem w/ the string drive . . . but was hoping for a solution not requiring removing all knowbs and dropping the front panel. Thoughts/suggestions appreciated.
Alan K9MBQ


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