PREFACE..................................................................................................... ii READ THIS! ................................................................................................. ii WARNINGS.................................................................................................. iii SAFETY SUGGESTIONS ............................................................................ iv General Troubleshooting.............................................................................. v 1.0 General Description ............................................................................... 1 1.1 Main PC Board Revisions ................................................. 1 2.0 Power Supply 1 2.1 Battery Backup .................................................................. 2 2.2 PUP Circuit ........................................................................ 2 3.0 The 8031 ................................................................................................ 3 3.1 Reset ................................................................................. 3 3.2 Memory Mapped I/O.......................................................... 4 3.3 Keypad I/O......................................................................... 4 3.4 MIDI I/O ............................................................................. 4 4.0 DM3AG ASIC ......................................................................................... 5 4.1 Mask ROMs....................................................................... 5 5.0 Analog Signal Paths ............................................................................... 6 5.1 Drum Signal Output........................................................... 6 5.2 Piezo/Data Slider Input...................................................... 6 5.3 Tape I/O............................................................................. 6 5.4 Tape Output....................................................................... 7 5.5 Tape Input ......................................................................... 7 6.0 Test Procedures ..................................................................................... 7 6.1 General Testing ................................................................. 8 6.2 Internal Diagnostics and Hidden Keys .............................. 8 6.3 DAC Adjustments .............................................................. 8 7.0 Updates and Corrections ....................................................................... 9 7.1 New SRAM Supply Circuit................................................. 9 7.2 Glass Zener (D15)............................................................. 9 7.3 Dirty Cliff jacks................................................................... 10 7.4 Ground CE......................................................................... 10 7.5 RF resistor ......................................................................... 10 7.6 10K MIDI Resistor (R5) ..................................................... 11 7.7 MIDI Pullup ........................................................................ 11 7.8 RF Shields ......................................................................... 11 7.9 LCD Contrast Adjustments................................................ 11 7.10 DAC Drift ......................................................................... 12 7.11 Old Keypad PC Boards ................................................... 12 7.12 Lifting R41 ....................................................................... 12 7.13 Reset Capacitor............................................................... 12 7.14 Sram Capacitor ............................................................... 12 7.15 Tape Capacitors .............................................................. 13 7.16 RF chokes ....................................................................... 13 7.17 AQ reset threshold .......................................................... 13 7.18 AQ R116.......................................................................... 13 7.19 Volume Slider Wiring....................................................... 13 7.20 PUP Capacitor................................................................. 14 8.0 Common Solutions ................................................................................. 15 9.0 Service Parts List ................................................................................... 18 10.0 Software History ................................................................................... 20 11.0 MIDI Implementation ............................................................................ 23 12.0 Service Manual History ........................................................................ 31 INDEX........................................................................................................... 32