I purchased a Bridechamber Rev3 PCB for the Wogglebug as discussed on the Electro-Music forum.  There are fourteen 1206 surface mount capacitors on the topside of the PCB.

Wogglebug schematic errors:

  1. Pin numbers are wrong and the + and - inputs are reversed on the schematics for U5 and U6.  The PCB is correct.

  2. Pin numbers are wrong, the + and - inputs are reversed, and U7 is shown as U?A on the schematics.  The PCB is correct.

  3. Pins 1 and 3 are reversed for V2, V3, and V4 on the schematics and PCB.  The controls mount off the PCB so reverse the connections.

Required modifications:

  1. Add a 4N7 capacitor and change R35 from 470R to 1K to increase stability.  The capacitor is added on the back of the PCB between the R35 / V1 node and ground.

Wogglebug schematics (with corrections #1, 2 and #4)  updated

Wogglebug Mouser parts list  updated




The LFO Out is a +/- 5 volt level fixed 7.4 mS negative pulse (top trace).  I decided this output would be more useful as a 5 volt positive pulse to use as a variable clock and trigger generator (bottom trace).  I also added a Rate LED and jumpers to select 5V or 10V CV outputs.

Additional modifications:

  1. Add a Lumex green panel LED to indicate the internal clock rate.

  2. Change U6A to inverting summation amp for +5 volt clock out. (Having later done the 50% duty cycle mod #10 below, I wouldn't have done this mod.  The output would have been a +/-5V square wave.  I still would have added the LED/resistor as shown to pin 3.)  Schematic has been updated.

  1. Added jumpers to select 0-5V or 0-10V range for Woggle CV,  Smooth CV, and Stepped CV.  Change R42 and R43 to 10K with a two pin jumper in parallel. Change R20 to 2K with a three pin jumper to connect a second 2K in parallel or in series to ground.

Assembly Notes:

  1. I used 1M log taper potentiometers for V2-V4 and wired them as follows:

    Potentiometer pin connections
    Control Function CCW Wiper CW
    V2 Woggle Range V2 pin 1 V2 pin 3
    V3 Woggle Time V3 pin 1 V3 pin 3
    V4 Smooth Range V4 pin 1 V4 pin 3


  1. +15 volts measured 28 mA (without LED), -15 volts measured 21 mA.


After the module was built, I decided I wanted the Clock Out to be a 50% duty cycle instead of the 7.4mS positive pulse.  The rate was high enough that I could divide it by two to generate a square wave.  Since U4 was in a socket, I used a header with a LM555C and a 74C74 which required no modifications to the PCB.

Clock 50% duty cycle modification:

  1. Add a 74C74 clock divider on an 8 pin DIP header to divide the rate by two. (Now having done this mod, I wouldn't have done #6 above as the output would have been a +/-5V square wave).




The three traces cut for the clock modification are all hidden and I used R8 and R40 for two of the clock mod resistors.  The third resistor is mounted on the rear of the PCB.  This photo also shows the three jumpers I added to select the CV level.


I made the two 2-pin jumpers by bending the leads to fit the PCB layout for R42 and R43.  I then soldered 10K resistors between the legs and inserted the jumper into the PCB as shown in this photo. 
The three pin jumper was a bit more challenging.  Since only 1 pin soldered into the PCB the other pins slide in the plastic housing.  I potted the two resistors and pins in epoxy to eliminate any movement and then soldered the jumper in the PCB as shown in this photo.  The wire goes to a nearby ground via.
Here is a side photo of the PCB showing the jumpers installed.


Wiring complete.  The MTA insulation displacement connectors in the Mouser parts list have insufficient clearance for three of the closely spaced headers: J2, J5, J8.  I substituted FCI mini-latch connectors which will work with the MTA headers although the pins are 0.065" too long.




I built a temporary panel by using a spare MOTM-120 panel and printing a matching design on a laser printer.   I glued it to the front of the panel and sprayed it with two coats of lacquer.  The lacquer seals the page and gives it an orange-peel texture with just a bit of sheen (left).

After using this module for a while, I chose to design a FrontPanelExpress panel instead of using the Bridechamber panel because I wanted a Clock Out multiple (right).  This provides a single external clock for use with my three ComputerVoltageSource and PSIM modules.


Wogglebug FrontPanelExpress file