[HAM] troubleshooting the vibrato scanner

[Phil Glatz]

I'm working on a Hammond T-312 that had been in storage for some 
time.  I cleaned things up and oiled the motor, and the vibrato 
scanner was working OK.  I cleaned the drawbars and tablet switches; 
things are less noisy, but the vibrato is not working. I hooked a 
dual-trace scope to the signal going into the scanner and the signal 
coming out, and appear to be getting a good waveform on both 
sides.  If I use the switch to turn vibrato off, my scope display 
goes flat and the sound is slightly different, but there was no 
vibrato when it was on.

I'm guessing it is something mechanical with the scanner, probably 
just coincidental that this stopped working when I cleaned the 
switches.  It looks like quite a chore to get to the scanner unit, 
and am wondering if anyone with more experience might have some 
troubleshooting tips or places to compare signals, to make sure it is 
truly the scanner?  SInce this hasn't been run for many years, 
perhaps some part might have frozen up?