Madbean Sharkfin odd behaviour

[SpaceCommandant]

All seems fine and in proper working order; the samples are jumping around to the various pitches.
There comes a point, though, when the pitch gets 'stuck' on Low.
Example:
High-Low-Low-Med-High-Med-High-Low-High-Low-Low-Low-Low-Low-Low-Low.........
The effect resumes proper functioning as soon as I adjust the speed knob.
Then, within a couple of minutes, it's back to getting stuck on the Low sample.
I'm curious if anybody has any ideas what the issue could be..

[clockman]

 I'm getting the same thing, I thought it was me not dialing in the trim pots properly or not choosing the right transistor.
 I settled on a 2n3391A instead of the 2n5088, felt like it was more lively with its range of sounds and character. I did try a lot of different transistors. also bf245A for the fets instead of J201.

 It does "lock up" on lower frequencies then goes more random and back and so on.
A point to note: I got the same results with the Sabrotone layout as well.
So is it component choice, trimpots dialing, both and or something else?

 Anybody getting similar results?

[Beaker]

I've built one, but I used a Madbean PCB. It worked perfectly from the off, so I have not experienced your lock-up problems.

However, it won't be your trimpots that are causing the problems - they are just for dialling the "glitch" action. There is no right or wrong setings, you just set them where you think it works best - usually with a roughly even amount of up and down note changes.

Sorry I can't be any more help.

[clockman]

I was considering a Pcb but then Alex was kind enough to post his layout.

 was wondering, do you remember going through a lot of transistors to find the "right" one for your build?
I've popped in quite a few, several of many different kinds of types of models of brands and makers and vintages etc.

 and it's always good to hear from you. thanx.

[Beaker]

No I did not experiment with transistors.

As everything I read about this pedal suggested that it was a potentially troublesome build, I just went with Madbean's parts list. If I remember correctly, the only substitute I made was using a 1N5818 instead of a 1N5817.

http://www.madbeanpedals.com/projects/Sharkfin/Sharkfin_2015.pdf

The only modification I made was to change one resistor value to get a faster maximum rate.

I was extra careful to check every component for function and value before soldering it in place.

I haven't got it with me at the moment, as my son has it in his studio. I can get it back if you want some measurements.

I guess it's just possible that there is a small error on the layout that has not been spotted? Unlikely really as Alex is amazing at getting layouts right first time.

[nocentelli]

It's worth trying the "aquataur mod" if you're struggling to dial in a decent noise setting (especially if you have socketed the noise transistor so it's easy to try out): Use the base to -9v (instead of collector), connect the emitter as usual and leave the collector hanging.

http://aquataur.hilpold.net/aquataur/musicstuff/fsh-1.html

[clockman]

Beaker, thank you for the offer of voltages etc. but I just Tried the "aquataur mod" as suggested by Nocentelli and it seems to be working  fine, well and stable with the first 2n5089 transistor I popped in. almost afraid to adjust the trimmers now. I may not for a few days.

Nocentelli, Thank you for posting this! This is indeed a wonderful community here.
I hope SpaceCommandant, who started this thread, sees this and has similar good luck.

[Beaker]

I tried to read everything I could about this pedal before building, but never saw this, so thanks for posting it Nocentelli.

So problems occur if the circuit is not noisy enough? Makes a change from the usual too noisy issues I guess.

I'm glad you have got yours fixed Clockman, especially when it's such a simple mod.

Go ahead, don't be scared , tune those trimmers!

[SpaceCommandant]

Thanks for the suggestion!
So far, it seems to be working perfectly with no lock-up.
As I understood it, I took the base of the 5088 (in my case, a 2222A) and soldered it to the collector.
I love this effect on droney synths.