bob at jfcl.com
Wed May 14 13:09:14 CDT 2008
Now that my TD8E is fixed (maybe - I'm keeping my fingers crossed here)
I'm having problems with the TU56 drive electronics. Nothing works, neither
the diagnostic (DHTDAB) nor the OS/8 drivers.
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.
If I understand the way the TU56 works, then this a) about 15x the
frequency I'd expect to see on the timing track and b) I wouldn't expect
there to be an output from the TT when the tape isn't moving. Am I right
that this is really screwed up, or do I just not understand how it works?
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