MSW-810 Build Notes
This page contains build notes and FAQs for the MSW-810 DIY Kit. It is a work in progress and will continually be updated as questions come up.
BILL OF MATERIALS (Spreadsheet)
Interactive iBOM (Placement)
BOM Notes:
- Resistors: any 1/4 watt 6.3mm long, 5% carbon / 1% Metal film can be used.
- Film Capacitors: Lead spacing is 5mm
MAINBOARD ASSEMBLY
Notes/FAQ:
- Resistors marked "MF" indicate 1% Metal Film parts (the blue ones)
- There are NO wire jumpers, all jumpers are routed (do NOT stuff wires)
CALIBRATION
POWER
Power calibration simply involves trimming the 12V rail to exactly 12.00.
With all chips inserted, power up the device and adjust the trimmer marked "12V ADJ" (Yellow) while measuring test point marked "12V" (Green).
Check the other test points in the circuit to make sure you have +5VDC/-5VDC/+9VDC (green)
the blue arrows indicate connections to COM.
VCO CALIBRATION
Calibration is a standard analog VCO calibration. There are several ways to do this but this is the method I use:
Controls:
VCO FINE TUNE (VR1/RED)
VCO OFFSET (V2/YELLOW)
VCO TUNE (VR11/GREEN)
Required Tools:
Voltage source: CV Keyboard, PVR, etc
Frequency Counter: Counter/Scope/DVM/Guitar tuner. Scopes and DVMs are not terribly accurate at lower frequencies so a tuner may be more appropriate
Procedure:
Connect voltage source to CV input, adjust controls as shown below and center both the VCO FINE and VCO OFFSET pots to their center position. Set sliders to the following positions:
Connect SYNTH OUT/J1 to your frequency counter.
- Send 1.000V/C2 Note to the CV IN jack.
- Measure/Note the frequency of the output
- Send 3.000V/C4 Note to the CV IN Jack
- Adjust the VCO OFFSET pot until the frequency is 4x that of when you sent 1V. This pot is VERY sensitive so only tiny adjustments are needed
- Send 1.000V/C2, adjust the frequency with the VCO FINE pot to what it was in Step 1.
- Repeat steps 3-5 until the frequency at 3V is exactly 4x the frequency at 1V
The important thing here is span on the frequencies, not the actual frequencies, I find it is easiest to do with higher frequencies so I set the footing to 8'.
Once that is sorted, send the appropriate voltage/note from your keyboard (i.e. the A440) and adjust the pitch of the note with the VCO TUNE trimmer (GREEN). You may need to adjust the footing for this to work correctly.
IF YOU CANNOT GET ACCURATE TUNING, THE RANGE OF THE OFFSET TRIMMER CAN BE ADJUSTED BY CHANGING R99 to 1K5
PWM
Required Tools: Oscilloscope
With the same slider settings as VCO Calibration, lower the Saw to 0 and raise the Square to 10, adjust the PW TUNE trimmer so your square wave has 50% duty cycle
VCF CALIBRATION
Required Tools:
Voltage source: CV Keyboard
Frequency Counter: Counter/Scope/DVM/Guitar tuner. Scopes and DVMs are not terribly accurate at lower frequencies so a tuner may be more appropriate
- Set Controls as indicated
- Holding 3A Key, adjust VCF FREQ slider to approximately 1kHz
- Alternatively playing 3F and 4F Keys, Adjust VCF WIDTH until 4F doubles 3F frequency
VCA
Since there is no official service doc for the 810 available and this feature was not available on the 202 or 101, adjust to suit. This trimmer controls the exponential gain of the 2nd CV controlled VCA.
