TU56 question...

[Eric Smith]

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.