Destructive Imaging of DECTAPE II Media

[Mark J. Blair]

> On Jan 31, 2015, at 02:42, shadoooo <shadoooo at gmail.com> wrote:
> 
> 
> This procedure could work?

From the research I've done so far, I think that the heads on your 4-track should have gaps in appropriate locations for reading (but not writing) TU58 tapes. I don't know if this will work, though, because normal audio cassette speeds are much slower than in a TU58 drive, and it is my understanding that the signal level received from magnetic tape heads is proportional to the tape speed. Normal audio tape speed is 1-7/8 inches per second, while TU58 tapes normally move about 30 inches per second during reads. That's a really big difference!

My gut feeling is that you would need to modify that 4-track to run the tape at much higher speed in order to get a usable signal from the heads, and by the time you sped up the drive enough to do that (assuming it's possible), the resulting signal would be at high enough frequency to get cut off by the sound card's input antialiasing filter.

This is why I'm expecting to need to make my own read channel circuitry and sampling hardware, even though I'm contemplating the use of some sort of (heavily modified) regular cassette tape transport for the mechanical part.

I think that if you have a "disposable" tape (preferably one that has already been verifiably copied by some other means, known to contain unimportant stuff, or a segment of tape from a cartridge that is already not fully recoverable due to some obvious damage), then there would be no harm in experimenting with this. We could least get some empirical data about what sort of signal levels come off the heads at 1-7/8 ips. I'll probably do something similar if and when I make more progress on this, but you might get around to it long before I do. :)

Regarding your rusted drives, I may have one or two TU58-XA units that I could spare for a fellow 11/730 buddy. These would not be complete drives; they're just the tape transport mechanism. They would be untested, dusty, and would need the capstan roller rebuilt, but if your drive electronics are still good, then maybe they would help you out?


-- 
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/