Hi, all. I could really use some help on this one. I recently purchased an
old Pioneer RT-707 in great shape except for two issues:

Tape speed does not change when tape speed button is pressed (tape is
mounted). It's not the capstan or pinch roller, solenoids, or dirty switch.
I don't have a schematic to troubleshoot further. Any ideas.

Also, On the top circuit card that the bank of switches is mounted to
(Power, Tape Speed, etc.) there is a fried diode clustered in a group of
three components directly behind the "Bias" switch. The other two components
are a 330K ohm resister and a red-coated resister or something. If anyone
knows what these do and what the component parts are, I would really
appreciate it. I have an old RT-1020 that I may be able to pull parts off of
for replacement. Thanks in advance.