PDP-12 Restoration at the RICM

Jay Jaeger cube1 at charter.net
Tue Dec 22 20:56:51 CST 2015

On 12/22/2015 7:31 PM, Michael Thompson wrote:

> Lots more work on the PDP-12 at the RICM. We got an RS-232 console board
> and baud rate generator from Vincent and now have both serial ports
> working. Warren modified Kyle's SerialDisk and we booted OS/8 from an
> emulated RK05 on the second serial port. We fixed one of the bus interface
> boards in the DW8E Omnibus expansion chassis, and connected the RX8E/RX02.
> We were able to boot OS/8 from an RX01 diskette. We replaced an M160
> flip-chip and now the EAE instructions work. We replaced an M103 flip-chip
> and the KW12 clock works. This system is new enough that ECO EM12-0055 for
> the KW12 was installed when it was built. This means that the KW12 Maindecs
> earlier than D8CD will not work. We cleaned up the PC04 paper tape
> reader/punch and connected it to the PC8E. The punch works OK, but the
> reader does not always step correctly and does not read the tape correctly.
> Fixing this will be the next project.

I have an image of MAINDEC-12-D8CD-PB, and a listing as well
(MDEC-12-D8CD-L in my inventory).  Let me know if you need them as well
as the drawings (see below).  It is in an archive folder with a bunch of
other interesting PDP-12/PDP-8 stuff.

Can you give me a pointer to the SerialDisk info?  Sounds interesting.

Hopefully you can actually fix the original M160 and M103 cards.
> Once we get the PC04 working the next project will be the RK8E/RK05.
> Out of frustration we set aside fixing the TC12 LINCtape controller. We see
> spikes on data track #3 that corrupt the data. We swapped the TU56 for a
> known good TU55, swapped the data/control cable, and swapped every
> flip-chip that is related to data track #3. Nothing has eliminated the
> spikes. The only part that we have not swapped is the backplane wiring
> between the data cable and the G882 flip-chips. Warren has a plan to
> temporarily replace that.

Maybe just run another wire.  If the wire is temporarily opening, that
would fix it.  But, if the existing wire is shorting to some *other* pin
(which is a distinct possibility, of course), another wire may not help.
 If it doesn't, then you presumably do have a short to another pin -
look at where it passes near other pins.  Or maybe just start with that,
and measure resistance from the wire(s) in question to the post(s) that
they come very close to?

> We found that the maintenance prints that came with the system do not
> include ECO EM12-0055.
> Does anyone have a set of KW12 prints that include ECO EM12-0055?

Looks like mine do, with the ECO dated 12/71.

Affected drawings that I detected:

CLEB Input Chn 2
CLEC Input Chn 3
CLR Clock Rate
Engineering Specification

Mine also include Rev. B - EM12-57, dated 6/72.  Affected drawings:

CLC Clock I/O Control

Shall I scan them in?


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