Phil Allison wrote:
"Chris F."

I have a Teac Model 80-8 1/2" open reel machine I have to
repair
for a customer. This is the first 1/2", 8-track machine I've
worked
on and it's clear I'm going to need a schematic. The main
problem is
that some channels are sounding through to others; for
example, with
a signal connected to channel 1 only, it sounds over to
channel 2
and faintly to channel 3. This happens even when monitoring
the
input without a tape loaded, ruling out a head alignment
issue.
Any advice, or especially a schematic, would be appreciated.


** Have you tried shorting the unused inputs while testing ??

This is how the recorder would be used in practice.

If that doesn't eliminate the crosstalk, I'd suspect a common
power supply filter in the low-level stages. Perhaps a dried-up
cap.