Delay guitar pedal into synth module

[Silesius]

Hi, I'm trying to modify a Digitech Digidelay pedal to use in my eurorack modular [I can't afford an Echophon right now]. So far, I've managed to adjust the levels, using the CGS stompbox adapter, and add some voltage control over the time parameter using a vactrol.
The pedal uses the usual pushbutton [spst off-on] to engage it, but this button has other functions as well. It works as a tap tempo button [to sync the repetitions] and it is used to put the looper in record mode [it has a looper too!].
So I thought it wold be great to put a jack in my front panel where you can engage the button by sending clocks and gates to it. That would make the pedal a very useful delay in a modular context. You could remote control the looper and sound on sound functions, and sync the delays to a clock [not an Echophon, but good enough ].
As said, the switch is very simple, it just has two poles; I measured the voltage and I found 3.3v on one pole and about 0v on the other. So I thought that if I send a 3.3v gate to the 0v pole I would be faking a button push. But that's not working. All the components are smd, and I'm not very good with technical questions, so I'm not sure about how to do next. It seem like an easy mod, but now I'm stucked.
Any ideas about this? Maybe I could use something like a cmos 4066 to engage the button??

[Boogdish]

You should try sending zero volts to the +3.3 side. It might be that a pin has a pull-up resistor, and the switch is grounding out this pin.

If you're unsure about this, and want to check before potentially damaging your equipment, find a known ground point on the pcb (like where the power supply comes in) and measure the resistance between that point and the cold side of your switch. If the resistance is zero (or a negligibly small number) then, the switch is meant to be a path to ground.

If you can find the voltage regulator that's providing 3.3 volts, you can then check the opposite. If there is significant resistance between the 3.3 volt supply and the hot side of the switch, then it's going through a pull up resistor, and it's safe to ground out at this point.

So, if you're wanting to ground it out using positive trigger/gate pulses, you will need an inverter. A 4066 should work, I would put a diode between the 4066 and the board, that way you don't have to worry about having too high of a voltage on the 4066 output damaging the delay, and you can still use the normal button when you're not controlling it with the synth.

[Silesius]

Thanks a lot Boogdish. It's working now with the 4066. I have 4 seconds delay perfectly in sync with the clock. Now it's time to put this baby behind a nice fron panel