Moonshot Tremolo not tremming?

[consumptive]

Hello. Just built the Moonshot Tremolo and it currently only works as a boost. The Gain knob functions while the pedal is open, and the top LED pulses in time with the Speed control. But there's no tremolo sound and when I put the back plate on the pedal or cover the red LED in the middle, the pedal goes silent. I'm assuming I messed up the LEDs — can anyone point me in the right direction?

The build docs only specify a 3mm red LED for D1. But there are 3 spots for LEDs on the board and none of them are labeled or numbered. I put the 3mm red LED in the middle of the board, right above the LDR, and 5mm blue LEDs in the other two spots. Gut shot below. Please correct my ignorant mistake — thanks!

 

[pbrommer]

So far, I think you have the LEDs in the right spot. You probably need to point the ldr toward the 3mm red led. Does the red 3mm blink and change when you adjust knobs?

Voltages help as well. I think you’re close, but just one little thing away from success.

 

[consumptive]

Thanks for the quick response! The front-facing LED on the top of the board blinks and changes when I adjust the Speed knob, but not the red one. What do you mean by point the LDR towards it? Do you mean rotate it 180 degrees on the board? This is the first pedal I've built with an LDR and a quick google search said orientation didn't matter, so I just tried to match the board silkscreen. Guidance here would be much appreciated!

 

[Erik S]

What do you mean by point the LDR towards it?

I think he means like this:



The LDR disc responds to the light from the LED. The angle affects how much light hits it. The circuit may also not work correctly with the cover off due to light from the room hitting that LDR all the time.

The 3mm LED should be pulsing in time with the tremolo and should change speed and intensity with the knob controls.

Is your LED oriented correctly?

The side with the small flat and short leg should be in the hold with the square pad marked K. I can't tell from the picture, but it looks like it might be in backwards.

 

[consumptive]

Oh interesting — thank you, that's helpful. Did not realize the LDR needed to be mounted vertically. Have unfortunately snipped the legs on the other side of the board but can try desoldering and adjusting. Pretty sure the LED is oriented correctly, but can try swapping in a new one to be safe. Would it have the same effect if I raised the LED and tilted it over to cover the top of the LDR?

 

[Erik S]

Oh interesting — thank you, that's helpful. Did not realize the LDR needed to be mounted vertically. Have unfortunately snipped the legs on the other side of the board but can try desoldering and adjusting. Pretty sure the LED is oriented correctly, but can try swapping in a new one to be safe. Would it have the same effect if I raised the LED and tilted it over to cover the top of the LDR?

Can you see the small flat in the plastic on the edge of the LED? See if you can verify if it's facing the right way before you jump to replacing it. You will need to figure out why it's not blinking though. If it IS facing the right way, the next thing I would do would be to triple check all your component values.

Folding the LED over the LDR will get you the same result as moving the LDR. I try to do it in a way where either the LDR or the LED can flex a bit so the gap can be adjusted.

 

[consumptive]

Extremely helpful, thanks — will try those steps and see how it goes...