Table of Contents

Testing the VCO

To properly test the VCO, you need to do 2 things. 1 generate a CV signal, and 2 check the waveform. This can be done with multi-thousand dollar waveform generators and oscilloscopes or with 2 AA Cell batteries taped together and a cheap pair of headphones.

Must have your Power Supply Tested And Calibrated! The 5.333V is a very important piece of the x0xb0x puzzle. Having it wrong will screw around with any other future testing and calibration.

Testing with good equipment

(someone else needs to write this.)

Testing on the cheap

Make sure the Power Supply is connected, and plugged in. First Center VR2, TM4 and TM5. Connect 2 AA batteries together, and then attach that to R90. With a pair of cheap headphones, you can attach the sleeve to ground using a wire with alligator clips (A good grounding point is R179 also known as pin 2 of J4 ). With this set up, you can probe pins 1 and 3 of the switch. Pin one could make a buzzing, and pin 3 should make a slightly different buzzing. (Hopefully you know the difference between a saw and a square wave!) You probably want to use some cheap headphones, what you are after is high-impedance (32ohm) headphones.

Depending on the headphones you use, the signal might be super low, so make sure it is a quiet room.

Also, you are probably going to start off with lots of static and noise as your hand moves around. Try to keep a steady hand.

Tuning the VCO

To tune the VCO, you need to provide 2V and 3V power at the end of the resistor network (where R88, R89 and R90 meet), and before the opamp (IC 11, pin 5). Generally this means some kind of variable power supply such as "a thousand dollar arbitrary waveform generator, or a 9V hooked up to an LM317 & potentiometer." A gate/CV keyboard works just as well however, as it will generate exactly the voltages you need.

Tuning the VCO Without a Benchtop Power Supply

It is much easier to tune the VCO after you have the sequencer section built, rather then before, as it can generate the required voltages to tune it.

Tuning the VCO Without a Frequency Detecing Multimeter or Oscilloscope

Guitar tuners work just fine. You can also 'tune by ear' as it were, but it is not going to be perfect. (See OscillatorDrift)