EHX Small Stone Phasor LFO

[bobloblaws]

Hello, I have a vintage EHX Small Stone Phasor pedal here that passes signal but there is no oscillation/phase shift. I went as far as replacing the electrolytic caps and IC's and transistors, but to no avail. What I've done now is recreate the entire circuit on a breadboard, but I have the same problem, its passing through the signal but the LFO is not working. Any troubleshooting ideas are most welcome, thanks.

[mozz]

I can't see it not working on a breadboard and same problem as the pedal. Does not make sense. 

[Kevin Mitchell]

It doesn't make sense. User error? Check the wires to the color switch.
I would like to know where people are getting their long discontinued CA3094 ICs from.

[PRR]

> I would like to know where people are getting their long discontinued CA3094 ICs from.

That may be the key question. If the 3094 is blown, or fake, signal will still pass through the dry path. It won't "phase" unless you have shifted signal mixed with dry signal.


Lift the 30k resistor to kill the dry signal. Is anything coming through the shifty path?

[bobloblaws]

> I would like to know where people are getting their long discontinued CA3094 ICs from.

That may be the key question. If the 3094 is blown, or fake, signal will still pass through the dry path. It won't "phase" unless you have shifted signal mixed with dry signal.


Lift the 30k resistor to kill the dry signal. Is anything coming through the shifty path?

Thanks for the replies, everybody. PRR, you might be on to something about the chips being fake. I plugged the original IC's into the breadboard project and now at least I have some oscillation. However, the pot's range is fast to hyper-fast and there is not a lot of depth. (I'm seeing DC volts on pin 6 of the LFO chip fluctuate between 5 and 6 volts).  Also, the signal is getting to the output with the 30K resistor lifted, but I am not hearing any phasing when the dry signal is mixed back in. I don't think any of the IC's are blown because when I probe the audio signal it is equally strong all along the chain. I'll have to go back and double check everything in case I made an error that is preventing the phasing from happening. Or is the phasing aspect also dependent on the LFO working correctly? Sorry, I don't know exactly how everything is supposed to operate in this type of device.

[bobloblaws]

Thanks for the replies, everybody. PRR, you might be on to something about the chips being fake. I plugged the original IC's into the breadboard project and now at least I have some oscillation. However, the pot's range is fast to hyper-fast and there is not a lot of depth. (I'm seeing DC volts on pin 6 of the LFO chip fluctuate between 5 and 6 volts).  Also, the signal is getting to the output with the 30K resistor lifted, but I am not hearing any phasing when the dry signal is mixed back in. I don't think any of the IC's are blown because when I probe the audio signal it is equally strong all along the chain. I'll have to go back and double check everything in case I made an error that is preventing the phasing from happening. Or is the phasing aspect also dependent on the LFO working correctly? Sorry, I don't know exactly how everything is supposed to operate in this type of device.

It's working! It turns out there was an issue with the pot, changed that out and now the speed is where it should be. Also, the reason I wasn't hearing the phase shift is because I had a sine wave going through it (duh!). Plugged in a guitar and it sounds bona fide! Now I'll take note of the voltages around the circuit for reference, then figure out why the circuit on the pedal wasn't working. Thanks everybody!