MK11 box controller, or M8159 board schematics

From: Jules Richardson <>
Date: Sun Nov 7 16:45:30 2004

Was fiddling with our Decsystem 570 this weekend. Seems like we may have
a PSU fault as the left-hand M8728 MOS memory boards in the crate don't
have a lit green LED on the top, whilst the right-hand boards do. Tried
the obvious swapping memory boards around and the associated A/B control
boards with no luck, and according to the bitsavers docs a problem with
PSU B would knock out that portion of the memory crate's bus.

Anyway, I'm looking for either the schematics for either the MK11 box
controller, or for the M8159 data buffer board.

In particular I need the pin connection diagram for the 40 pin ribbon
cable that runs between the box controller and the M8159 board.

Our Decsystem 570 never had a box controller; instead it had someone's
homebrew attempt at half a box controller - a bunch of LEDs on a single-
width board plugged into slot 26/F of the memory crate, and a couple of
SPDT switches grafted onto the edge of the M8159 board (yuck!). Slot 26
in the MK11 appears to be a spare; someone's added wires beneath to
connect three of the LEDs back to the power supplies, so I know those
are doing the equivalent of the battery status LEDs in a real box

However, there's three more LEDs on the homebrew board that are soldered
directly to various pins on the box controller connector of the M8159,
and the two bodged switches are connected up to pins here too.

The two switches are unlabelled, so knowing the pinouts of the box
controller connector is the only way of working out what they do.
Working out what the three unknown and unmarked LEDs are for would be
handy too!

The manual for the MK11 doesn't go into detail of connector wiring
though - any have the relevant schematics?


Received on Sun Nov 07 2004 - 16:45:30 GMT

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