debugging a tu58? blank tapes or bad read channel?

From: Brad Parker <>
Date: Wed Mar 31 13:18:46 2004

Does anyone have any suggestions about debugging a TU58?

This is a dual TU58 from a vax 730. The symptom is that when I try to
boot from it the tape rewinds a bunch of times and then reads off the
end of the tape.

I removed it and poked all around with a scope and the schematics. The
motor control is fine as well as the tachometer. The read channel shows
no activity, even when I put a tape in and move the tape. The micro
seems happy.

I connected it to "tu58ctl" and I can talk to it and send/receive
commands. But when I try to position the tape I get a "motor stopped"

I'm begining to wonder if the 3 TU58 carts I have have been bulk erased.
I have no "known goods" and I've never read these tapes. I made the
assumption they were good but that might be a mistake.

(wish I had those mythical proms which can write carts :-)

I put a scope on the signal from the read heads and I see nothing when
the tape spins by. I find that very odd. I would think I'd see pulses
even if the blocks where all zeros... So nothing makes me think the
tapes have been bulk erased.

Is there any way I can test the read channel without having a good tape?
(I assume not, but I know very little about tape drives, perhaps there
is some 'technique').

I know the tapes are useless if they have be bulk erased - but will the
symptom be no read channel activity? (I assume so).

blah. if I've wasted all this time on bulk erased tapes %$#%_at_#@!#$

Received on Wed Mar 31 2004 - 13:18:46 BST

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