[vcf-midatlantic] Weekend workshop report

Mike Loewen mloewen at cpumagic.scol.pa.us
Sun Jun 11 22:46:23 EDT 2017

    I worked on two projects at the museum, this weekend: my recently 
acquired Eagle IIE micro and the museum's HP 2117F display system.  The 
Eagle is a 4MHZ Z80 system (CP/M) with 64KB RAM and SS 5-1/4" drives.  The 
display was out of adjustment, with a "doubled" presentation.  A quick 
tweak by Ian on one of the video pots fixed that, and I resoldered the 
leads to the reset switch which had been inexplicably cut by a former 
owner.  Nice bright and clear display (green CRT), passes internal diags.

    The HP 2117F is a circa 1983 mini, with a hardware floating point 
processor module.  I pulled the power supply and checked the inside of the 
top cover for the infamous black form: yep.  It hadn't quite started to 
disintegrate, but it was just a matter of time.  I removed the foam and 
glued a plastic shield in its place.  The power supply voltages were 
close, but I adjusted them to spec.

    The system wasn't completing its self-test, and didn't seem to be 
recognizing its RAM.  It turned out to be a missing ribbon cable which is 
supposed to connect the RAM boards (3 boards of 256KW each) to the 
controller board.  I pulled a donor cable from our ugly 2113E hangar queen 
and the memory tests now pass.  I also replaced 3 broken plastic toggles 
on the front panel with parts from the 2113E.  I showed Evan how to toggle 
in a short program from the front panel to make the lights dance, Cylon 
style.  To paraphrase a line from the movie, "Firefox": you MUST think in 
octal.  :-)

    The 2117F is missing a couple of crucial controller cards to connect to 
the peripherals in the cabinet: the HP-IB interface for the hard disc, the 
7970B tape drive interface, and the interface for the 13037C disc 
controller.  Fortunately, the 2113E has the requisite HP-IB card (12821A) 
so it may be possible to check out the HP-IB drive in the future.

Mike Loewen				mloewen at cpumagic.scol.pa.us
Old Technology				http://q7.neurotica.com/Oldtech/

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