Circuit Benders Modded ROLAND TR77 Analogue Drum Machine with MIDI

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"For over 15 years we have been creating and supplying aural havoc with rewired childrens toys, modified drum machines, abused samplers and audio insanity machines, but as space has become a prized commodity here at the circuitbenders bunker, we've decided its time to shift some of the massive and ancient behemoth drum machines that have gathered over the years

First to go is this Roland Rhythm 77 or TR77 as it was also known. The TR77 was the first machine to ever be released under the Roland name way back in 1972, and it bears a remarkable similarity to the Bentley Rhythm Ace FR8L, mainly because they are more or less the same machine!

The TR77 is one of those massive 'sit on top of your organ' (no sniggering at the back please) type of drum machines that were popular in the 70's. Theres absolutely nothing digital in this thing, and that includes the remarkable pattern generator circuitry for the 28 onboard drum patterns that can be selected via the front panel buttons. Several buttons can be selected at any time to combine patterns for more complex rhythms.

There are 13 fully analogue sounds onboard, most of which are generated using old inductor-capacitor 'tank' circuits. You cannot get much more analogue than this without hitting something with a stick!
The sounds include Bass drum, Snare, Low Conga, Low Bongo, High Bongo, Rimshot, Cabasa, Clave, Tamborine, Cymbal, HiHat, Maraca and Guiro.

Our upgrades include:

Midi triggering for each of the 13 sounds. The midi channel can be selected using the 16 position rotary knob on the rear panel. The midi doesn't sync the patterns, but if you wanted to do that then you might as well rewrite them via midi triggering and then you can alter them as you want.
Internal pattern generator on/off switch: This is the new switch on the rear panel. It disables the pattern generator board when you are using external midi triggering so that clicks and pops caused by the internal pattern triggers are silenced.
Recapping: All of the electrolytic capacitors in the machine have been replaced and upgraded. The originals were not only underspecified, but were also about 20 years past their reasonable working life!
Power supply rebuild: The original internal power supply circuit on these units is appalingly bad, and causes a ridiculous noise floor of AC hum and interference making a normal TR77 almost unusable in any modern context. We've pulled out all the junk that was in there and replaced it with a more or less silent modern power supply. More details on this mod can be found HERE.
IEC mains socket: The new power supply runs on any common mains voltage, so we've added a standard power cable socket that can be used anywhere in the world.
A red LED: We drilled a hole in the wrong place. Now its got a power LED in it. ;-)
The standard TR77 features such as the variable fade out button, the various individual level faders and the fantastically pontless 'up tempo' switch are still in place and fully functional.

You can here a quick demo of a TR77 being triggered via midi on our soundcloud page [above]"