Roland CR-78

The CR-78 CompuRhythm is one of  THE  Classic Drum  machines from Roland.
It's quite small compared to a 808 or 909.

DIMENSIONS:
300(W) x 280(D) x 205(H)mm
11.8″(W) x 11.0″(D) x 8.1″(H)
NET WEIGHT:
5.5 kg/12.1 lbs

It was made famous by its use by prominent pop musicians. The machine  featured in  "Vienna" by Ultravox, "Heart of Glass" by Blondie and "In the Air Tonight" by Phil Collins.

These come dressed either in wood or black
There are 5 sliders, 31 buttons & 5 knobs

5 sliders, 31 buttons, 5 switches and 5 knobs

5 sliders, 31 buttons, 5 switches and 5 knobs

5 sliders, 31 buttons, 5 switches and 5 knobs

RHYTHM SELECTION BUTTONS:
Rock 1-4, Disco 1-2, Waltz, Shuffle, Slow Rock, Swing, Fox Trot, Tango, Boogie, Enka, Bossanova, Samba, Mambo, Chacha, Beguine, Rhumba.

VOICES:
Bass Drum, Snare Drum, Rim Shot, Hi-Hat, Cymbal, Maracas, Claves, Cow Bell, High Bongo, Low Bongo, Low Conga.


CANCEL BUTTONS:
Cymbal + High Hat, Bass Drum, Snare Drum, Cow Bell + Claves.

It was the second drum machine to use a microprocessor. (That honour belongs to Paia's Programmable drum set).

Ikutaro Kakehashi (The founder of Roland Corporation) says that at the time the only CPU choices were the MOS Technology 6502 and the intel 80 series.The 6502 was difficult to get in japan so the 8048 won out.

  (the 8 bit CPU - NEC D8048-C015)

This was a very important advance in drum machine technology. Users could now program and store their own drum patterns

8 bits CPU NEC D8048-C015Users could now program and store their own drum patterns By tapping you could create your own pattern. You could also combine this with one of the preset patterns.

OUTPUT
Start/Stop, Variation (DP-1, DP-2)
Write (TS-1)(TRIGGER PULSE OUT)

TRIGGER PULSE SELECT IN SWTTCH:
8 Beat, 16 Beat, Combination.
The external clock input accepts a clock of 12 ppqn (pulses per quarter note), which adds up to 48 pulses per bar/measure on a four-four time. The signal should be between +5V to +15V, and have a length of min. 5ms. A Doepfer A-146 LFO produces just what you want .... a +5V symmetric pulse wave.

EXT. CLOCK (trig out):
0 to 15V pulses. min. 5ms width

A Pedal Switch DP-2 & Write Switch WS-1 (Roland programmer)

Roland programmer

are useful accessories

You can trigger the CR-78 with the following Eurorack modules :

• A-146 LFO II
• A-155 Analog/Trigger Sequencer
• A-160 Clock/Trigger Divider
• A-161 Clock/Trigger Sequencer
• A-180 Multiples

See link 7 below for more info.

Links: 
1. Fenix I & III (and a Roland CR 78) 
2. CR 78 Midification (AnalogueSolutions)
3. Roland CR-78 CompuRhythm with Modifications - Demo Video 
4. Roland CR-78 non-rechargeable Lithum battery replacement mod
5. Astronaut
6.  Warren Cann from Ultravox  (his experiences modding the CR-78)
7. Triggering, Syncing and Programming a Roland CR-78 with Eurorack
8. CR-78 repairs & internal pics
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For more info on the history of Roland Drum Machines click here