Yet another idea for recovering the data from Series80 tapes

Background: The problem with the old HP 9162-0061 data cartridges is that the magnetic coating peels off from the (transparent) tape causing the machine to stop accessing the tape with an EOT warning. This is actually very good news because it means that the damage is localized (a few mm of tape with scrapped off magnetic coating). BTW here is a picture of a damaged tape: http://www.series80.org/Articles/DamagedTape.jpg My guess is that the magnetic coating gets scrapped off the tape during fast motion (rewind or fast forward), so presumably if you simply advance the tape over the heads at normal read speed (10 ips) the tape will survive for a single pass (there are two tracks on the tape, but since the head is not moving, I assume that you can read both tracks at the same time). Now since we have only one attempt, and we are likely to encounter errors, I do not want to have the Series 80 firmware involved in the process. I would like to simply record the info (via a PC) to a .wav file and then process that file to see if anything can be extracted. Proposal: To do this I would need to manually rewind the tape till the BOT sensor, mount it on the tape drive and advance it past the read/write head till I run out of tape (tape unspools from the supply reel). While this is going on I am recording the output of both heads via the audio in port of my PC sound card (maybe use two separate sound cards to avoid cross talk?). Data extraction rig: 1) audio connection: what kind of set-up would be required to connect the heads to the audio card. From the schematics I see that there are essentially three connections to each head: Head 0: H0, CT0, and HC Head 1: H1, CT1, and HC (HC is common to both heads) But I am not sure what these are used for. 2) running the tape at a constant 10ips. There is a circuit that uses the tachometer wheel to control the tape speed, but again I am not sure how to program (?) the tape controller IC (U1) to move the tape. (I may need to disable the BOT/EOT sensors, but that should not be a problem). I am lucky to have a 9915A as my test bed which allows far easier access to the tape drive mechanism than the HP-85 (and does not have these evil ribbon cables). Unfortunately I do not have a scope, but I can borrow one for a short period if necessary. I have a logic analyzer. ------- Another idea that just came to me as I was re-reading this email, is that I can possibly allow the read/write IC (1820-2418) to do the analog to digital conversion for me, ans simply read a stream of bits (with a time reference). Is this approach better/worse? Perhaps I can do this in parallel with the audio recording. (if the 1820-2418 is only able to sample one track at a time, I can use another 1820-2418 for the second track). Any suggestions are welcome. Best Regards **vp www.series80.org