[rescue] How to open a TK50Z-GA?

[Mouse]

> This may help

> https://lastin.dti.supsi.ch/VET/tapes/DEC-TK50Z/EK-0TK50-TM-002_Jul86.pdf

Thank you!  I managed to find a work machine to fetch it from (I have
no HTTPS support on my own machines, and lastin.dti.suspi.ch is not
willing to serve it over HTTP).

> Under section 3.4.2 lights
> Flashing:
> Pushing the load/unload 4 times may clear the fault.

I connected it to the TZK50, since I note there is a good deal of
drive<->controller interaction going on, even a sense pin that lets the
drive tell whether it's connected.  Powered them both from the same
supply (not the H78948BA).  This should operate same as in the case but
with no SCSI cables connected.  Turned it on.  The red light on the
TZK50 came on, as did the load/unload light on the TK50.  I did
nothing.  After a second or so the light on the TZK50 went out.  A few
seconds later the load/unload light on the drive started fast-flashing.

I then pushed the load/unload switch eight times (eight because it's
not clear to me whether the "4 times" refers to four presses or four
full cycles).  It went solid red at the first press and stayed that way
until I was done.  I then left it (button out).  After a few seconds,
it went back to fast-flashing.

> That being said lots more info in there that may help

There is indeed.

I find myself wondering whether the problem is with the drive or the
controller.  Chapter 2 describes enough of the communication between
the TZK50 and the TK50 that I am tempted to snoop on the DR CMD and DR
STATUS pairs - or possibly the internal versions of those; I see a
26LS31 and a 26LS32 right next to the drive connector on the TZK50, so
I'll be looking for pinouts for those.  Makes me suspect I might even
be able to cobble together something to talk to the drive directly.

/~\ The ASCII				  Mouse
\ / Ribbon Campaign
 X  Against HTML		mouse at rodents-montreal.org
/ \ Email!	     7D C8 61 52 5D E7 2D 39  4E F1 31 3E E8 B3 27 4B