Floppy tape drive

[John Campbell]

I acquired a new 3b1 with a floppy tape drive.  Now I have
the following problem:  The floppy tape drive works fine in the
new 3b1 and in my friend's 3b1 but not in my "old" 3b1.  All machines
are 3b1's with at least 2 Mb of memory.  The machine that doesn't
work fails with a "Floppy Tape drive is not ready".  Running the
floppy tape diagnostics says something like:

Floppy Tape Controller found 
Testing Floppy Tape Controller Circuitry:

DMA data R/W .. OK
DMA addresses R/W .. OK
WD2797 reg R/W .. OK

Floppy tape drive not ready
Floppy Tape controller test sucessful.

Then the 1-4 menu comes up and all tape functions continue to report
Floppy tape drive not ready.  This is despite the fact that the tape
has finished retensioning, etc.  Try to believe I'm doing the tests
right as I did them repeatedly on two systems last night and one system
always worked while the other always failed.  Also, on the 3b1 that
fails, I moved the board to each of my 3 slots.  The tape diagnostic
software always seemed to find the board in the right slot and told
me "Floppy Tape Controller Test Sucessful."

This "old" machine is one that failed to boot (marching boxes) until
I adjusted the power supply.  Now it seems to run fine--passes normal
diagnostics and reads/writes fine from both the hard disk and floppy
disk.  Like my friend's machine, it has the vidpal and WD2010 chip
installed.  Since my friend's machine can access this floppy tape
device I'm assuming these add-ons aren't involved.

Is there a separate chip on the motherboard that might have gone bad
on this 3b1?  I'm desperate to get the floppy tape working with the
"old" machine as it, in fact, has a 2Mb motherboard and the replacement
machine came with a .5Mb motherboard and a 2Mb expansion board.
The expansion board and a DOS board, by the way, seem to work just
fine in slots on this "old" machine.

Anyone have any ideas?  What signal is "tape drive ready" anyway?
How would the mother board know the difference?  (I'm using the same
cable, tape drive and controller board in all experiments.)

PS--note that pins 1,2,20 don't seem to be connected in the cable.
The cable still works, however, on at least one machine so I guess
this is not a problem--but it gave me a false lead for a while.
-- 
	John Campbell               jdc at naucse.cse.nau.edu
                                    CAMPBELL at NAUVAX.bitnet
	unix?  Sure send me a dozen, all different colors.