Sound Technology ST 1000A SCA Calibration

The SCA channel occupies the space from 60 to 74 khz, and its center is 67 khz.

You may have to look up the "FM stereo transmission standards" for allowable SCA center frq. tolerances.

Do you have a trim cap C44A as shown in the schematic? If yes, then adjust it for exactly 67 khz with the function sw. in SCA mode.

Art

The FM generator of the choice is Leader 3216.
 
Adjustment of the trim cap may not be enough to bring the the oscillator back on frequency.

Check the values of the carbon comp resistors around the modulation oscillator. You will likely find that they will all be at the top edge or slightly out of of tolerance. It is well known that carbon comps do not age well and will have drifted high in value.

I recently re-calibrated 4 ST1000's that all exhibited low modulation frequencies. Replacing these resistors with 1% metal films put the oscillator bang on frequency without further adjustment.
 
Adjustment of the trim cap may not be enough to bring the the oscillator back on frequency.

Check the values of the carbon comp resistors around the modulation oscillator. You will likely find that they will all be at the top edge or slightly out of of tolerance. It is well known that carbon comps do not age well and will have drifted high in value.

I recently re-calibrated 4 ST1000's that all exhibited low modulation frequencies. Replacing these resistors with 1% metal films put the oscillator bang on frequency without further adjustment.