neovibe only works when speed pot is cranked

[zolee]

Hi everyone,

 I just finished my neovibe according to the plans posted at generalguitargadgets. The pedal sounds great, only it cannot produce slow oscillation. When I turn the speed pot ccw, it acts as the depth pot: oscillation evens out, the bulb is glowing. For this reason only a very fast speed of oscillation can be dialed in, making this great sounding pedal pretty useless.
I also observed that when I turn the power on, the lfo produces a few slow flashes, but it evens out then. Can anyone help me? Thanks in advance for your help.