Hammond 102100 -1974 - 1975

    Weight = 34 Lbs. Number manufactured = ~200? MSR = $1500

User Manual: My scan
Reset Proceedures: N/A
Operating System code: N/A<
MIDI or other control protocol: N/A
Software related Links: N/A
Patches or knob settings:
Circuit Overview: below
Scematics/Service Manual: Organ Service Company or My scan
Common Service Issues/Tips: below
Parts Sources: Keys knobs semiconductors misc
Uncommon chips/modules used: Custom hammond 7-stage divider 001-047298-001 aka 075-047298, AMI S2555 and S2556 TOS pair
General Info Links: Vintage Synth Explorer and My Video demo on youtube.

Circuit Overview:
     Monophonic single VCO machine with preset selections for voicings AND for envelopes etc. Only Volume, Tuning and 'Wind' get a slider on this one (wind being a noise source). Repeating what I've heard, these are one of the rarest of synthesizers produced by a known company I guess we can say. The Crumar DS-1 having fewer produced but possibly more of them left in existence. Anyway this machine generates a digital code from the keyboard for octave/note value. Then integrates it into a logic pattern to route the proper frequencies and footages in keeping with switch panel settings.

Service Tips:
     Connectors can be switched or reversed so watch for that. Interconnects can have some strain and break wires that are difficult to see particularly with coaxial lines to volume control etc. The tuning is fairly touchy on the vcf. Wrong settings = useless sounds pretty much usually. See my 102100 video as a tutorial. Also note that we had a very elusive problem where C#'s would sound whatever the previous note was. Ie. the gate trigger was working but no informaiton was being sent. There was very little movement I noted on the C# buss but normal gating signals on the individual inputs. But everything on the other side of the resistor was very small change. I swept across things and believed I'd found a bad solder joint. I resoldered the area as I couldn't see a specific problem and it worked for the whole video I did and a while more...then failed again! Finally after some plausibility analysis I caught the intermittent leaky diode in the act! Anyway I guess if you run into a similar problem I'd first just replace all the cheap diodes there with 1N4148 that are associated with junction from the note you are having trouble with, unless you can detect the leak with diode checker reversed of course.

Lots of discrete parts. Ask if you need a specific part.
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