[rescue] Trying to get Cadmus 9200 running (serial console trouble)

[Meelis Roos]

Some time ago (last year? or 2017?) I wrote about rescue of 5 sets of 2-box
Cadmus 9200 computers. Now I finally got around to sorting them out to decide
what to leave for myself and what to send out to those in the queue.

Yesterday I dug them out.

The sets all seem to be Cadmus 9230 (some parts are from 1987, some from 1988):
Cadmus 2800 main box with QBUS cage and no storage and Cadmus 2804-62 storage box
with 65M SMD disk and 16M QIC tape drive (4 boxes have tape drives, one misses the
tape drive). All main boxes have MC68010L10 CPU, 512M RAM board (directly connected
to the CPU board), Emulex SMD disk controller (4-wide), 8-port serial mux card
(4-wide) and a 2-wide tape controller card, 3 also have parallel port card (4-wide)
with MC68000-10 CPU on it.

I happily found that there is virtually no dust inside to clean before plugging in,
and tried to get some output. Just from the main box, no storage attached. After two
days of trying and reading manuals, I still have no output at all.

The two boxes I used most have three front panel lights and they are on (well,
one lamp is out on one of the boxes but I know the lamp should be on by swapping the
lamp panels around). The lamps are "RUN", "LTC" (line to clock) and INIT and they
should be on normally, according to the manual. So the box thinks it is somewhat alive.
If I remove some QBUS boards, the lamps still light on powerup, except when I remove
the CPU board (then RUN goes off, as would be expected).

I tried 3 different cables to two PC-s (one Dell D600 with native serial, one a later
Thinkpad with pl2303-based USB-serial adapter). Tried with and without a null modem
adapter with all the cables to be sure that I have at least one correct twistedness.
9600-8N1 as the manual says, and tried both hardware flow control and no flow control
(by the manual, most ports should have no hardware flow control lines connected, only
console and another port have it, no explicit mention of whether the console port
should have hardware flow control).

Reseating all the QBUS cards did not change anything.

With one unknown black cable and no null modem adapter, I got some strangeness: there
is partial echo back of what I type, but that is garbled (about 1 out of 3 characters
is the same, 2 are garbage that is different for each character). Interesting part is
that I only get echo for 4 last serial ports (including console on 8) but no echo on
first 4 serial ports. Might that be some strange pinout of the black cable that is
somehow activated by remote port handshake?

Does anyone have any ideas how to continue? I want to get the systems up to the point
where I can at least see which hard disks might still be working (for sorting).

-- 
Meelis Roos