The Drumulator was the first sample-based affordable drum machine based after the Linn Drum and Oberheim DMX public success .
The classic 8 bits Z80 ZILOG CPU manages 8 channels polyphony and each channel features a assigned samples. The Drumulator contains 12 PCM waveforms (bassdrum, snare, tom (x3) clave, cowbell, claps, hihat open/closed and ride cymbal) coded at 8 bits resolution stored on 4 A-B-C-D socket EPROMS for a mere total of 64 kb. NOTE: TOM channels are filtered by 2 famous chip SSM2044 (static but powerful).
More info HERE
Got at an ebay auction at nice price with Midi fitted and extra banks rom with analog switch. In the past I sold all my drumulators , I still don't know why, they sound good and have and incredible design that matches the SP12 and Emulator II. The machine starts up but the sound is distorted, like old circuit bending. Buttons seems also not to react and the machine is quite filthy... as you can see.
UPPER: Well , it URGES to give a good cleaning to the blue beast. After cleaning it shines! now we're talking. Now let's open it. Just a couple of screw under the hood. Pay attention to the underneath TO-3 Transistor isolated with plastic.
UPPER: The internal is is pretty good condition. Second thing to do is removing the eprom board and the DIY midi interface to access the full board. All sounds are distorted, also in the separate outs, and with all rom banks, so it's not corrupted EPROMs.
UPPER The main structure. tracing with oscilloscope, the signal seems to be stuck between level dac and the DEMUX. It's clean after the main dac and somehow get troubles after,
UPPER Following the DAC 6072, the signal is correct after 2d opamp LF356 pin 6. The signal then enters the Level DAC ad 7523 at 5. Something happens between 7623 inverting and non-inverting that go into the 6c op. How strange, the voltages differences are 3 volts at 2-3 6c. Let's remove the Opamp and check it.
Upper: well the opamp was good and innocent. Sooooo.... the culprit seems to be the level dac interstil AD7523. Found one on the market at reasonable price. Le'ts wait with crossed fingers! in the mean time some more cleaning for buttons and sliders.
Data slider 100Kb is not soldered and easy to clean. Buttons are quite hard to remove from board, you can clean them or replace them, but prices are quite high.
All seems working now , sounds are now clear!
Some files for you:
- Drumulator service manual download.
- ad 7523 datasheet download.
- factory eproms download with OS midi.
- DMX88 datasheet download.
Need some assistance? custom eproms? spare parts? contact us!
If you like our work, please to buy a sample pack from our section to help us.
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