Easy way to work out whether changing the speed pot would help, is to work out what the resistance is, when the oscillator is at it's slowest. Time to get the multimeter out.

If it's at 100KΩ when it's slowest, changing to a 250K pot might help. If it's at 0Ω then adding a bigger pot would give you faster speeds instead of slower.

Be aware that deviating from the design might have unintended side effects. Maybe 100K is the highest 'stable' value, and above that the oscillator doesn't run properly. Only way to tell is to try!

If I were you, rather than break a 1900kr pedal, I'd invest 500kr in the kit, which is super cheap, and you can run flyleads or add a pin header to let you try different values without resoldering the PCB every ten minutes. Good luck!

- "The Mysterious" Tqi.

Last edited: Apr 28, 2018 04:35:22

Thanks so far everyone

I soldered a 1M linear pot in series to one of the outside lugs of the speed pot. I can't remember which one. You have a 50% chance of doing it right the first time.:)

I choose a 1M linear pot because you need exponentially more resistance to go slower and slower. As posted previously:
0k extra : 210 bpm (slowest stock)
55k extra : 196 bpm
155k extra : 182 bpm

You'll see an additional range of 14bpm (210-196) with 55k ohm extra, but you need almost twice (100k ohm) for the same additional range of 14bpm (196-182).
You will probably need an extra 200k Ohm for the next additional 14 bpm. Hence my choice for a 1M pot.

Last edited: Apr 28, 2018 17:58:57

Cool! That would have been quite a puzzle! Looking forward to the next one with battery power.

Already got plenty of shrink wrap, thanks...

I used it mainly to keep the PCB from moving around in the case (not enough room for stand-off clips), and to keep the LED from falling out of its hole (didn't have any LED sockets at home).
And while I was at it, I put some on the tabs of the jacks, but more for keeping the board from moving, rather than for isolation - shrink wrap wouldn't have helped with that...

Pretty sure my tremolo quest is over now I've had this thing kicking around on my board for a while. Nice and simple and does exactly what I need. I'm running it at 12v. Layout is a little goofy, so I might rehouse it in a bigger enclosure and put a foot switch in place of the toggle.

Last edited: Jun 04, 2018 00:49:04

j_flanders wrote:

I soldered a 1M linear pot in series to one of the outside lugs of the speed pot. I can't remember which one. You have a 50% chance of doing it right the first time.:)

Hey I'm planning on building my kit this weekend with a 3PDT switch, but while looking at your schematic I was wondering why didn't you choose to use the switch GND and pin at the top of the board between the power in and the output section? instead of interrupting the circuit at the LED

Last edited: Jun 15, 2018 17:33:14

Lechero wrote:

Hey I'm planning on building my kit this weekend with a 3PDT switch, but while looking at your schematic I was wondering why didn't you choose to use the switch GND and pin at the top of the board between the power in and the output section? instead of interrupting the circuit at the LED

I drew that schematic before I had the kit. I didn't know if the led would stay on/blinking if you bypassed the effect because the led is connected to the oscillator.
You can read about my questions and Björns answers over here in the other SurfyTrem thread:
https://surfguitar101.com/forums/topic/28106/?page=6#p401443

IIRC I wired my other Surfy Trem using that GND switch connection.

@otaznik That sounds like a nice solution. I might try that on mine.

Last edited: Jun 16, 2018 05:14:12

otaznik wrote:

I made a pedal with true bypass ... that vintage signal change even when not used which also means volume drop (this does not matter).

So I did this:

true bypass 3PDT:

in    return (footswitch gnd =ON)
send  out    (footswitch)
X     Y      (disconnected =OFF)

DPDT mode switch (original / true bypass):

in    return (always through circuit)
X     Y
gnd   in     (SEND to GND, bypass)

So in addition to 3PDT push switch I have another DPDT slide switch on the side which makes the 3PDT true bypass or lets me use it as designed.

Oh my gosh! this is so clever...
I sort of understand the conceptual idea, although I'm not absolutely sure I understand your diagram, so is it like this:

on the footswitch 3PDT:
     in   <pin1>    return <pin2>      (footswitch gnd =ON)<pin3>
     send <pin4>    out    <pin5>      (footswitch)        <pin6>
     X    <pin7>    Y      <pin8>      (disconnected =OFF) <pin9 ¿nothing?>

on the additional mode switch (original / true bypass):    
     in                     return (original mode)
     X <from 3pdt pin7>     Y      <to 3pdt pin8>
     gnd                    in     (true bypass mode)

Last edited: Jun 19, 2018 17:56:12