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Re: Revox varispeed

>>From: Mark HEWINS <hewins@musart.co.uk>
>>I got an old Revox B77 MkII (for tape echo and looping only) about 2 
>>ago-my choice. Does anyone have any information about the varispeed 
>>control* for this machine?

By some accident, I have the whole drawings of the B77. I don't know about
MkII differences but pinout must be the same:

1 Gnd
2 +12V
3 nothing
4 Control voltage

The control voltage runs directly to pin 5 of a NE555.
They design the controller with a LM301 as impedance converter. I bet its
not necessary. I remember having done such a speed control for a customer
in '84 and it was very simple, and it worked.
The pot in the controller is 10k lin and for the coarse setting, it has
16k2 to ground and 5k7 to +12V. They even use 1% resistors. Revox.
Just go ahead and try.
Or ask more questions.