hifi engine

is there an old version Revox A77 captan speed regulation board schematic?


i have a A77 which plays fine at 7.5 ips but can not work on 3.75 ips.

the switching signal of red AE1 (0/21 v) is available from switching board while switching to 3.75 ips but the speed is same as 7.5 ips.

the reading from Techno sensor is always the same as 1/0.6ms approximately.

in this A77. the capstan speed regulation circuit is discrete discriminator circuit instead the later monostable 555 circuit in Studer's service manual.

i would appreciated if i could receive an old version schematic to speed up my investigation.