Desoldering trimpots

hello again,
i’m failing to desolder the two trimpots i put in the wrong places on the SMR-4 board - i got “DC R3 5k” and “lowww R34 20k” mixed up :frowning:
how much difference does it make them being wrong?
i think my desoldering pump is rubbish and i tried desoldering wire too… and failed.
if anyone has either some tips on desoldering, or some other ideas, i’d be really thankful!
otherwise, i’m gonna have to take it to a guy and hope he has better skills or a better desolder pump.

thanks in advance!

R3 being 20k instead of 5k makes little change.

I never remember in which way it goes, but R34 being 5k might not give you the optimal cutoff range - either the sound will be too dark when the filter will be open, or it will be too bright and you’ll hear some glitches when the cutoff is swept to 127. Try the “epiano” preset (22, iirc) and if you have to hit the keys with a hammer to make it sound bright (it’s velocity sensitive), you know the cutoff range is not adequately tuned. If you’re more a fan of dark basses than shiny sounds, this might not be a problem at all.

While the Reso, V/Oct, and DC trimmers have a “right” setting, Lowww is more a matter of taste…

thanks for the quick reply :slight_smile:
i’ll leave them as they are for now and experiment with it for a while,
i don’t have a midi keyboard (hence the sync24 name), this is a step into the unknown for me, but i’ll try and hook it up to ableton (another relativley unknown area…) and see how i feel about the sounds.
i do want noise and dark basses, so this should be ideal!
no doubt i’ll be back with more questions, but for now thanks again for the great service!

Just curious: how did you intend to use a synthesizer without any kind of input device? Only with the built in Arp/Stesequencer???

Hey sync,

Sounds like you’re a bit of a novice. Desoldering is something with which this novice has had a lot of trouble, so be careful. If you have someone willing to do it for you that has, both the experience AND the tools, go that route. If it was me, I’d use it as an opportunity to ask plenty of questions with a front row seat to a personal demonstration. I think I ruined a Shruthi control board trying to desolder a 40-pin socket. A few of the metal connections around the holes came of with the solder. I don’t know enough to try and fix it. I thought maybe a connectivity pen, but from what I’ve seen of online demostrations, they are way too clunky for such fine work. Anyone have suggestions? Here’s a pic…Don’t judge me.

PS. Check out Pure Data, sync24. I just discovered it and it seems really cool for making your own midi controlled software instruments. I haven’t had too much time to really explore it but this site seems like a good start.

@CheeseNoOnions: I’ll have a dozen of PCBs available for sale soon. Let me first pack all the kits and do a precise inventory of what I have left.

hello, thanks again for the replies :wink:

regarding my lack of controller: i like limitations, so i will really try and get my head around the internal arp/seq (struggling with limited time at the moment…).
however, i do intend to try it with a midi controller keyboard, but i don’t really have the space for one in my analog set-up.
i will try building some controller stuff in MAX, thanks CheeseNoOnions, PD is good, but i teach MAX now and again and have been using it on and off for ten years, so reckon i’ll be playing with that to build some control environments :slight_smile:
i’ll also be getting into abit of Ableton Live, so will try controlling it with that too.

i <3 CV/Gate and pre-midi din sync the most though

CheeseNoOnions: tough deal with the desoldering, i will be going to visit the chap and get him to sort it out for me at some point. getting frustrated is no way to behave around hot soldering irons and lovely circuit boards! i think this novice has been relativley lucky... i've built a Dronelab and the two boards for a Klee sequencer, without a hitch, slow and steady wins the race... until i lost it a little with these bloody trimpots.... ha ha hame!

thanks! :slight_smile:

Do you have the specs for DIN sync? If its level is less than 5V I’m pretty sure that you can hack the Shruthi-1 into syncing to this through the CV inputs on the digital board.

This is where the 4 CV ins are read . Instead of pushing the values into the modulation matrix, you need to parse the sync signal and start/step/stop the clock accordingly. This can be done with:




(these are the handlers for the MIDI clock events).

Oh and if you do that, decrease the priority of the MIDI task to 1, and increase the priority of the CV reading tasks to 6.


If you don’t mind me asking about MAX, is there a way to do it on the cheap? I like that pure data is free. When I checked max for use with ableton, it looked cost prohibitive. I’ve also made the dronelab :). I want to build some kind of CV to midi or vice versa circuit so I can chain everything together.

i have absolutley no idea about electronics! i’m enjoying following instructions as carefully as possible :slight_smile:
i do have a couple of midi > din sync convertors (a kenton midi in / sync24 out and a tr727) which i will be using, though.
as for the code side of things… even less of an idea!
i tried learning SuperCollider, and got really confused.
i teach software at university, but avoid code as much as possible, the closest i get is flash and really basic actionscript2.
max, however, is like lego to me, i find it really simple (unless i need to do something related to maths, then i slow down…).
thanks for the pointer though, maybe someone else will do something with them…

the cheapest way to do max is as a student, you can even get a 9 month version… which you can upgrade.
do you know any students?
i bought it before they did student discount in 1999 :frowning:

regarding your Dronelab, are you part of the soundcloud group?
i’m Droneface.

i picked up a roland mpu-101 a few years ago for around £100, thats good for midi > cv.
it has four seperate cv/gate outputs plus some other stuff i haven’t used… pretty solid machine
have a look at what these guys do:
i’ve been meaning to investigate further, but theres a usb>midi/sync/CV box i think…

happy days!

I work at a university. I’ll look into it. I’m not part of the soundcloud group, but I’ll join at some point. I saw a roland mpu-101 on ebay for $700! You’re killing me sync24!

@pichenettes I just ordered two PCBs, thanks.

went along to see Gerald yesterday and he desoldered the two trim pots and swapped them into the correct positions :slight_smile:
he was heating up two of the legs at a time and pushing each trimpot from side to side to get it out… now why didn’t i think of that???

after plugging it all back together and switching it on, it sounded a lot better than before.
so now i just need to try and understand the dreaded MIDI and get some control over this lovely little box of fun!

…oh and i need to understand whats going on with how to do the tuning

help, lol!

For desoldering I have two newbie tips: 1) buy a little round back of copper solder braid, it whicks up solder underneath if you apply it with a soldering iron above. As the wick gets silvery you trim it off with clippers. 2) I tried a spring loaded syringe and went back to a cheapo radio shack/tandy hollow solder tip with a suction arm and bulb mounted above. It works great! But let it get good and hot bfore you apply it. And presqueeze the bulb and when you see the solder go liquid/smoke let go of the bulb. Also when it cools squeeze the bulb out in a cleaning area to "spit out the old solder or you run the risk of one day accidentally sending old reheated solder out onto the board your working with.