Roland TR77 Rhythm Machine

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"Roland TR77 Rhythm synth.
The Roland Rhythm 77 drum machine was Roland's first product (formerly Ace electronics) - released in 1972. It is actually an updated and relabelled Rhythm Ace FR-8L.

It was one of a trio of drum machines released by Roland that year, offering features intermediate between those of Rhythm 33 (TR-33) and Rhythm 55 (TR-55).

It comes in a flat wooden case with a metal base and has a holding for scorebooks - was dedicated to put at top of an organ for rhythm accompaniment.

General Product Information:
Contents
* 1 Rhythms:
* 2 Instruments:
* 3 Some technical inside:
* 4 External Sync

Rhythms:
· Latin: rhumba, beguine, cha-cha, mambo, samba 1&2, bossa nova, baion, bolero, tango
· Rock: rock'n'roll 1&2, slow rock, ballad, western, march, jazz waltz, waltz, cancel
· 2beat & 4beat: bass drum, snare, fox trot, swing, parade, shuffle

Instruments:
Bass drum, snare drum, lo conga, low bongo, high bongo, rim shot, maracas, high hat, cymbal, tambourine, guiro, cow bell. Rim are used for metronome, too.
has a little mixer for: bass drum, snare drum, guiro, high hats.
has a tempo & volume fader; and a fade-out option : for start there's no button, it's a finger-sensitive touch-bar, supports double tempo.
the power switch is not a primary AC-switch.

Some technical inside:
There's no IC inside - only one VCA...
Left: transformer, rectifier, softstart.
Mid: master clock, 5 dividers, reloop & down-beat LED, diode matrix.
The 1st divider is connected to the tempo-up switsch for a 1:1 or 1:2 ratio, the 2nd ones for switching between the 4/4 and 3/4 clock - 1:2 or 1:3 ratio.
Right: the voice board, mixer & output stage. BD, LC, LB, HB, rim are passive circuits.
Bottom: the rhythm switches...
External Sync
There's a little possibility to use din-sync on this device.
Logic board: leftest transistor, on its right the base resistor, solder on lower pin the clock line. For start/stop - its like a pedal switch - just put a transistor serial into the male connector: gnd=emitter, top=collector, base=start/stop line.

Works best at 8 ppm clock, up-tempo off for best results. On up-tempo on the guiro & tambourine it sounds bad as they have a 2nd trigger input which they get from the 1st divider."