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 ignal 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