The Digital Minc-11

As you can see, very under construction.

H786 test setup H786 test
A first short smoke test without cards (EK-KDF11-UG-PR2_Mar79.pdf, page 02-20) revealed that the +5V looked ok, the +12V was only 5.6V and -12V was zero. No special exploding caps or smoke, so it could be worse. The next step was trying to find a service manual, but no luck so far. I did found the MP01074_MDL-23_MINC_Engineering_Drawings_Jun80.pdf, which contained the connection names and cabling between power supply and backplane (page 01_13). This solved the -12V mystery; it is not connected! Elsewhere, at, I found the H786 wants a minimal load of 2A for the +5V.
For proper testing, I removed the H786 and the mains entry unit from the system chassis. A load of 2 Ohm on the two spare contacts +5V and GND) on the H786 was a proper dummy load. This worked ok. +5V still ok and +12V too. The two 10-turn potentiometers on the right board are for tuning: left is +12V, right is +5V.
Mains unit mains unit The mains unit interior; it contains complex wiring for the mains voltage selector, a fuse, a big filter, a relay to disconnect mains and the mains inlet and outlet.
dual P7 two P7 connectors Another small mystery is the dual P7 pin set on the H786 main board. It actually carries a few signals; PWR OK, RTC and DC OK according to the drawing. Checking for differences, I found none. All signals are the same.

The MP01074_MDL-23_MINC_Engineering_Drawings_Jun80.pdf document at contains much info on the Minc-23 system.

Local links:

Generic links (mainly in the real PDP-11s):


Last update: 2014-05-17