On 10/03/2017 06:58 PM, Jay West via cctalk wrote: > HP manuals of the period are awfully detailed. They all have the theory of > operation section with a circuit walkthrough, etc. It could be helpful for > you to also take a look at the manual for the 13181 or 13183 controller set, > as you'll kinda be doing what that boardset does.
If you get a 7970B or -C, get the service+operation manual from the HP Museum. Al has a bunch of 7970 stuff on bitsavers, but not, I think (I could be wrong) the manual specific to the B and C models. All of the HP manuals have lots of detail (the drives had almost endless revisions and additions, which can be confusing if you're just trying to figure out what you've got)--and still, your drive may be slightly different. For example, I've got a -B made in 1984 and the write-protect mechanism doesn't match any of the variations in the manual. This was important to me as on of the microswitches was broken on mine. But now that I've got the -B outfitted with 7/9 track read stack, write protect doesn't matter so much. I"m still tweaking the various adjustments on the drive (have a dual-trace 'scope handy) and it's getting very good. Currently, I'm using it to read old 7-track tapes and create SIMH .TAP files on a (shared) SDCard. I used a generic STM32F407 evaluation board, mounted it on a hunk of prototype board and fit a 50 line ribbon connectors to it. Hookup between the MCU board and the connector was done with wire-wrap. The MCU board even has a battery-backed real-time clock on it, so my files are all correctly date-stamped. I got the 48-conductor edge connectors for the other end of the cable from Anchor Electronics in San Jose. For switching between the heads, I built a small board that bolts to the head mounting plate and contains a 34-line ribbon connector for the head leads and a 20 line edge connector for the read preamp--and 5 small DPDT DIP relays to do the switching. The relay coils occupy a couple of lines in the cable connecting the drive to the MCU, so I can shift between the heads under software control. So far, so good. --Chuck
