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Its an replica - not just another clone
Schematics and Service Notes:
Roland-tr-909-service-notes.pdf
BOM: (last upload 08/2021)
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| ID | Focus | Info |
|---|---|---|
| 1 | Wiring | You can use the MTA100 system from TE connectivity for example - |
| 2 | noisy/hiss | make sure to solder the potentiometer at all pins to have the correct ground - (the ground flow thru the outside pins / it act like a trace/bridge) |
| 3 | MIDI OUT | measure the transistor HFE value for the switchboard Q604 - a gain of 350 should be fine. otherwise it can happen that MIDI OUT doesn't work. you can also mod the MIDI Out : http://www.colinfraser.com/tr909/909mods/909midi.htm |
| 4 | Transistors | select the * S* Transistors to the same HFE to get a balanced gain on all voices. check the schematics for more details: q12 in Bassdrum q51 in snaredrum q20 in Low Tom q27 in Mid Tom q58 in High Tom Q71 in Crash Q85 in HH Q65 in Rimshot Q37 in Handclap Q33 Tom Noise - should be ignored or just use the same hfe as above |