PDP-8/E PSU Debugging (was Q-bus pinout)

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Fri Apr 9 20:15:01 1999

At 08:21 PM 4/9/99 -0400, CLASSICCMP_at_trailing-edge.COM wrote:
>I know that folks here have traiditionally objected to outside FAQ's
>when instead the issue could be resolved by dozens of E-mails, but in
>this case Doug Jone's *PDP-8 Summary of Models and Options* answers
>the question of 8/E vs 8/F quite nicely:

Too bad it's wrong.

It makes it seem as if there was a box that was designated PDP-8/E and it
had a particular configuration that was retired until the introduction of a
new box with the designation of PDP-8/F. This isn't supported by the evidence.

What really happened, and I have several independent confirmations of same,
is that the PDP-8/E system evolved into the PDP-8/F in a series of steps.
Depending on the date code the machine was configured differently.

The evolution vectors were as follows:
        Module updates - example M833 - M8330, M831 - > M8310
        Chassis updates - Long box, single OMNI BUS
                        Long box dual OMNI BUS
                        Short box single OMNIBUS Linear PSU on side.
                        Short box single OMNIBUS Switching PSU in rear.
        Front Panel Updates: Diode logic + 8v LAMPS
                        TTL logic + 6v LAMPS
                        TTL logic + LEDs in lamp sockets
                        TTL Logic + LEDS
        PSU updates - Long linear PSU
                      Short linear PSU
                      Short Switching PSU (types A and B)

At some point in this evolution some marketroid decided to change the name
from 8/e to 8/f. The OEM version of this platform was called the 8/m and
included an optional limited function front panel (although all 8/M's I've
seen so far had the programmers panel but that's only about a dozen so who
can say)

I happen to have an 8/e that is:
        Short box
        6v LAMPs plus TTL front panel
        Side mount PSU

I recently picked up an 8/e chassis that had the dual OMNIBUS backplanes.
It is this one that doesn't have a cover. It may have been mounted in a
desk, I don't know (it also didn't have a front panel but I can use my
other 8/E front panel with it)

My guess is that the evolution of the 8/E was driven by the introduction of
the 11/20 since these changes seem have occurred between 1970 and 1972. All
8/E's with date codes prior to 1970 appear to be the diode front panel
type, All 8/E's after 1972 appear to be either 8/F's or 8/Ms (until the 8/a
came out).

The 8/M and 8/F are primarily differentiated by different inserts/color
schemes, electrically they appear to be identical. The solder mask of the
front panel says "8/E"

That being said (and yes I've sent Doug mail on this but its not exactly
FAQ material unless you really want to restore them as I do) I'd appreciate
pictures for the cover on the long one since I can fabricate a cover then.

--Chuck
Received on Fri Apr 09 1999 - 20:15:01 BST