Future Retro 777 Modifications - Manual (Page 3)

Control voltages should run between 0 and +6v, avoid higher voltages than +6v or any
negative voltages!
NOTE: If you use a switching type jack you could wire the secondary CV input so that
when nothing is plugged into it, it allows the original CV IN source to control oscillator
B. To do this, wire the other half of the trace you previously cut to the switching terminal
of the jack.
Adding a CV in to control the filter’s cutoff frequency
External filter CV input
For this mod you can use the same procedure as the "secondary CV in for OSC B" except
obviously you won’t need to cut the trace for the switches as mentioned above. Locate
R37 (0 ohm) resistor and lift the lead that connects to diode D31, located just next to
R37. For this mod we will run a wire from the tip of the CV jack to be used, to the lead of
the diode D31 that was connected to R37. If you use a switching jack you can run a wire
from the lifted lead of R37 to the switching terminal of the jack. This way when nothing
is inserted in the jack, connection for the circuit will be as it was originally. Next, wire up
the jack’s sleeve to ground. Positioning of the jack is up to you.
With this mod you can use the CV type switch in the filter mod section to select how the
CV affects the cutoff frequency of the filter. You can use the CV amount knob to control
the amount of affect the CV has on the filter’s cutoff frequency.
Control voltages should run between 0 and +6v, avoid higher voltages than +6v or any
negative voltages!
Additional notes for those doing modifications
There are 2 hex inverters that are not used. These are in IC U3 (part type MC14584). This
IC runs between +6v and +12v.
Pins for the unused inverters are:
1. 5 input, 6 output
2. 9 input, 8 output