Bob wrote:
Poking around, I've discovered that the RTT
("Read Timing Track") output
from the drive has a constant square wave of about 400kHz (2.5us period),
regardless of what the drive is doing. It's there whether no matter
which unit is selected, no matter whether any unit is selected, no matter
whether the tape is moving or stopped, and even if there's no tape on the
drive at all. This is from checking the RTT output from the drive right
at the cable connector on the TD8E with a scope.
The G888 sense amps are designed to oscillate when no input is present.