Build Your Own Clone Message Board

I just finally got around to building my Lazy Sprocket kit that I got last year - once they were available again
It is definitely a Mk II version

It is showing all of the listed problems of a bad 2N5457 - no swell, trimpot has no effect, etc.
I tried a new FET from another vendor and now the pedal is doing something I wouldn't believe is possible - it is motorboating - like a bad Fender "blackface" tremolo oscillator.
Turn the Sensitivity Control CW so that you get sound with the effect on and you get a very distinct "put-put" as the note decays. Turn the Attack Control and the frequency of the "put-put" changes.
The VR3 trimpot has no effect - there is no sweep.
Something has apparently changed the Op-Amp to an oscillator. If this was a 12AX7 I could figure it out - op-amps are just so many "little black boxes."
I am running it on a brand new 9 volt battery so it isn't AC noise getting it.
It also "pops" when switched out sometimes.

It was late and after doing a complete check of each individual component (I hate 5 color resistors) and swapping the transistors (all socketed) I was too frustrated to do any voltage, etc. checks. That is next as is a signal trace.
I did find that if I touched the "negative" poles of C12/13 (the bare tops) the "put-put" stops and I pickup the local AM radio station.
I wonder if there is an issue with the Vref and/or the IC (741's can be unstable in general)

I know the unit does all sorts of amazing things except the one thing I want it do do
Any ideas as to what has possessed this pedal
Thanks
Mike

Pics please.

If you remove the JFET, what does the effect do?

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Removing the FET allows the signal to pass but at about 2/3 volume as bypassed
I checked the voltages
Battery with the effect on - 8.5 vdc
Va - reads about 7.2 on pin 7
Vref - 4.34 vdc

Still can't figure out how this circuit can motorboat like an oscillator and how the attack control can vary the frequency

Oscillation like you are describing would most likely be caused by a short that is connecting the output back to the input, creating a feedback loop. The fact that you don't get full signal level when the FET is removed suggests that the FET isn't the problem.

It certainly looks like you have a solder bridge shorting out between the output of Q3 and the circuit input. On the solder side of the PCB just above eyelet 5 between the two 1k resistors (R1 and R12). This would certainly create a feedback loop.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

Shows how a new set of eyes helps
I should always use my magnifier headset these days.

fixed the solder bridge - I had assumed they were connected - and that fixed the "motorboating."
Replaced the FET ( thank you to BYOC - this is great customer service) and the unit works

You are right, it is a very subtle effect.
Now to look at how to increase the sensitivity - works great with humbuckers but it is a little less so with single coil, or lower output pickups.

Thanks for helping
Michael

Great! You could try a boost in front of the Sprocket and experiment to find just the right level for a particular guitar.

Decreasing R19 and increasing C11 would theoretically increase sensitivity by allow more of the side chain signal to the trigger.

_________________
*patience is a virtue*

Please do not PM me. email is prefered. keith@buildyourownclone.com

thanks for the suggestions
Will try