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Hi all. I was gonna post this in general discussions as it is non BYOC pedal help but I was afraid no one who could actually help would see it. If this is a problem, then we can move it to general discussions.

I have a Uni-Vibe pedal kit that has and issue. Because of true bypass, the pedal is always on. This means, the tiny incandescent bulb is always blinking. In an attempt to correct this, I connected the grounds for the input, output, and power jack to lug 2 of the foot switch. I connect lug 3 to the main board ground. With the foot switch engaged, 2 and 3 are connected (bypass 1 and 2 are connected).

This fixes the problem. However, engaging the pedal creates a massive pop. Is there a way to quell this? I thought about placing a 1M resistor between the input/output grounds and the lug 2 but thought that would kill the ground. I know guitar amps use capacitors to prevent popping of the on/off and standby switches but I couldn't guess what value.

Any help is greatly appreciated.

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-Jamie

If you are switching the bulb on at the same time, it may not be easy to eliminate the pop. Assuming all the grounding is still correct the pop may be non-mechanical at all as the bulb lights up instantaneously causing a sudden shift in amplitude in the phase stages (this is just a guess). You could build a little circuit that lights up the bulb slightly slower at turn on but it would probably take some work to tweak it for the most desirable result (IOW, a transistor with an RC filter to control how quickly one pin of the bulb connects to the LFO).

My advice is just get a couple extra bulbs. They are inexpensive so if in the future one burns out you can replace it pretty easy. I have yet to see one die in any of my Univibes.

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RIP madbean v.1

Follow-up: also you could just use the "cancel" set-up from the original UniVibe. This grounds the LFO on bypass. It's probably a lot simpler approach. In those vintage units, the LFO is grounded but the signal still passes through the circuit. In a modern TB setting, you could have the best of both: bypassing the circuit altogether and disabling the lamp in bypass to preserve its life cycle.

Using this schematic as a guide, I think you just need to ground the base of Q13 for the cancel function.

https://4.bp.blogspot.com/-5J3L9R1_Chk/T_WXTQl5NqI/AAAAAAAABo0/K70MXGGHHVE/s1600/fv_sch_vint.gif

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RIP madbean v.1