Thanks for the tip on the jumpers on the back of the PSU, Tony. I have
manufactured a replacement and after reseating the boards, I appear to
have a working PDP-8/e CPU once more. I have misplaced a box of parts
(go figure) so am missing the bulk of my over-the-top jumpers, so the
core testing will have to wait for another day, but I currently have the
chassis and PSU sitting side by side on the table (the base from a scrapped
RM02), leaving me enough room for a hex-height 16K MOS card to hang over
the side of the OMNIBUS. Preliminary testing shows that all is well. I
can store and retrieve numbers from the MOS memory, enter run state, single
step and halt. All the bulbs appear live. I am only missing the knob off
the front panel so I have to guess what mode the bottom row of lights is in.
Next step - RX8E and try to boot OS/8. Failing that, back to the papertapes.
On _that_ note... one of the other goodies I unearthed this weekend is a
portable papertape reader used by DEC FS when diags still came on tape but
customers had moved on to VT52s... it's a PR/S01. I have zero docs on this
thing and have no idea what baud rate it defaults to. It is a 20mA device
with a male and female connector - one with 4 wires marked TERMINAL, the
other with 6 wires marked READER. How to hook it up seems obvious (I need
to unearth my box of 20mA cables). How to strap the TTY card less so.
I do have diagnostic tapes; as soon as a friend of mine loans me his 20mA-to-
RS-232 converter, I expect to back up four boxes of diags and utils (none of
which I expect are unique in the world - it's lots of MAINDEC and DECUS stuff)
I did attempt to place two different KK8A modules in the -8/e box in place
of the KK8E. Toggling the Load Address switch only incremented the MA
lights in either case. I do not know for certain if these particular boards
are working, but what is the expected behavior for the combination of a
PDP-8/a CPU and a PDP-8/e front panel? Is it supposed to work? I know you
can stuff a KK8E in a hex-height OMNIBUS box. That was a supported
configuration. Also, where can I get a diagram describing the function of
the DIP switch on the KK8A? ISTR that only one or two switches have any
beneficial effect, but it's been more than 10 years since I have had to change
one and I forget what they do.
Furthermore, is there a good page to reference for some trivial toggle-in
programs for basic test/checkout? I can write a couple, but if there are
some pre-done ones, I'd rather start there.
The eventual goal of _this_ box is to pass all tests, then move on to
repairing the TD8E/TU56 that came with it. When I used this box in college,
it used to work. Between then and when they threw it out, the DECtape stopped
working. I have boxes of tapes to go through/use/backup once it all works.
-ethan
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Received on Wed Oct 27 1999 - 00:31:36 BST