The DEC "KM11" is a diagnostic tool for older DEC PDP-11 CPUs and some peripheral devices.

km11 pcb

It's a passive maintenance panel with just 4*7 lamps and 4 switches, which can be plugged into special slots on the host device.

There's no own "KM11" manual, it's use and schematics are part of the device to be debugged.

The best overall description would be at .

KM11 is invaluable in repair, very scarce, but easy to build. So some people reproduced it, I throw in mine project here.

km11 100


km11 101

Main use so far was microstepping 11/40 and 11/05 CPUs.

Especially for that I added pinheaders, so the micro program counter on display can also be monitored with a logic analyzer. And the one "momentary action" switch for generating "micro-step" pulses can be disabled, so pulses can be injected via a variable highspeed square-wave generator.

Attached you find the PCB Gerber files, a 3D print STL for the light template, and paper overlay for 11/40 and 11/05 CPUs. -- Gerber files to produce KM11 PCB

km11.stl -- 3D print for KM11 light mask

km11-1105.pdf -- KM11 labels for 11/05 CPU

km11-1140.pdf -- KM11 labels for 11/40 CPU

km11-schematic.pdf -- KM11 schematics