PDP-8/L troubleshooting (was Re: New acquisition, and question)

--- Megan <mbg(a)theworld.com> wrote: -8/L with the kind remember them being 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 __________________________________________________ Do you Yahoo!? Faith Hill - Exclusive Performances, Videos & More http://faith.yahoo.com