11 Oct
2002
11 Oct
'02
2:06 p.m.
--- Megan <mbg(a)theworld.com> wrote:
Okay, it is a PDP-8/L, but I don't remember an
-8/L with the kind
of paddle switches this one has... I seem to remember them being
the rocker kind like on a pdp-8/I
All of my -8/Ls (3.5) have PDP-8/e-style toggle switches. My -8/I does
have the rocker switches you describe.
The 1970 Small Computer Handbook shows -8/Ls with paddle switches.
Still a nice find, though. My -8/L is currenly my showcase machine -
I fire up the ASR-33 and the PC04 (PC05?) and load FOCAL for folks.
It was also my first-ever -8 - Dayton Hamfest, 1982, $35 + 8" floppy
drive in trade.
Got some minor processor glitch I haven't tracked down yet... I get the
FOCAL prompt, but it won't load Hammurabi from either the ASR-33 or
the high-speed reader. Most of the basic functionality is there - it
runs an inchworm just fine. Once I fix the problem, I'll reattach
the BM08 and bring it back up to 12KW and show people paper-tape BASIC
and Star Trek (after I fix the tear in my floating-point tape ;-)
When you get to debugging it and if you see any behavior that leads you
to think there are hardware problems, after cleaning the card fingers,
take a hard look at any 7474 chips. I rigged up a test clip to an
automated IC tester to debug M-series modules out of the circuit (having
never written any software to drive my VIC-20 M-series tester) and
found that the most common chip to die anywhere in the machine was
the 7474 dual D flip-flop. Unfortunately, there are several of them
in the M220 Major Registers modules and this simplistic tester isn't
able to cleanly test them because of the multiple interconnects. I
have a small box of "to-be-repaired" M-series modules from my -8/L
collection. It's mostly M220s and M216s, with an occasional M160 and
M111.
-ethan
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