[Radio Wrangler]

The signal off of the tachometer transducer on the capstan motor bell should be a good representation of the speed and smoothness of rotation (not necessarily the smoothness of tape motion if the capstan is distorted or dirty)

The tach signal could be looked at with an audio spectrum analyser, an FFT analyser, or even a computer soundcard and FFT programme, looking for flutter sidebands on the intended frequency.

For listening or other tests I'd want trustworthy tapes recorded with simple tones, not music. Tapes from who knows where at different speeds are not necessarily innocent.

(I last took an A700 apart in the early 70s and I've forgotten most of it!) David

David