Hi, I've recently got around to try get and my MINC-11 working and not
getting very far! So I'm after advice.
Right now I have a minimal system consisting of
M7270 LSI11/2 CPU
MSV11 RAM
DLV11/J serial/console
PC PSU with reset circuit to generate BPOK and BDCOK
Here's a rough guide to what I've diagnosed so far:
1. Jumpered the CPU to boot into ODT and checked the jumpers on the
serial board for console address
2. No activity on the console port on power on or reset
3. Double checked the timing of BDCOK & BPOK and they're in spec.
4. Debugging on the DLV11 reveals the MATCH signal isn't being generated
from the address decode logic
5. The bus looks
partly correct. SYNC, BDIN & BDOUT look fine. The mux'd
data/address lines are active in the BDIN/BDOUT cycles but within those
cycles the signals "oscillate" (they cycle 20-30 times within a single
BDIN/BDOUT pulse, which doesn't look good!)
6. Probing around the CPU board now. All the signals look correct, with
the exception of the 16 data/address lines generated by the data chip
(1611). Power and all 4 clock phases look good as does the internal
data/control/microm WMIB bus and the WAIT signal from the control chip.
7. OK, so looks like the 1611 is faulty. I wanted to check it wasn't the
1611-Qbus interface circuitry so I "modified" a junk 40 pin socket to
sit between the 1611 and the on-board socket and removed pins 3-18
(hence isolating the WDAL0-15 signals of the 1611 from the rest of the
CPU board). This made no difference - the signals on those pins are very
weak (2V peak) and "spike" for very short periods at the beginning of
data read/write cycles.
So I'm stuck and I have no spare 1611 or other LSI-11 CPU module to try.
Does anyone have a spare 1611 or complete LSI11/2 they'd be willing to
lend/sell? I'm in the UK. Alternatively, any advice for other things to
check? I can try and grab some screen shots of the signals if that would
help.
Thanks for any help!
James