Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

Hi!
My circuit skills are non-existent but I was trying to figure out if it would be possible to lower the triggering voltage threshold in the trigger conditioning circuit so I could use microcontrollers with a 3.3v output.
If I understand correctly, lowering the values of R5, R12, R18 and R25 to, for example, 10k would have that effect while still keeping the current behavior for 5v triggers if I choose to use them later on.

I'm very possibly missing something so please let me know what you think.

Thanks

Hey
So I've been working on circuit bending my KAOSS Pad 2 / KP2. I had added a LTC1799 clock mod, a switch to hold the pad motion latch, and a patch bay of bannaa plug all connected to the RAM chip.

I'd been doing it over months, and stupidly forgot how to put it back together, and managed to put a crack right through the screen.

The screen is just two piece of glass with a resistance pressure strip around it, but it doesn't seem to work with cracked glass! I'm wondering if I should be able to just replace the broken glass with another piece, or replace the whole screen, or what other ideas there are out there. Feel like such a fool

well, just an update for anyone who cares:

I did eventually get some good advice from some people over on the synth DIY subreddit.

one person told me I needed to wire  a diode in series before connecting to the keyboard matrix, but we eventually determined that this wasn’t the case, as only the “n” column pins in the matrix have diodes, and not the “s” pins (the rows), which would be the ones containing these secret drum samples.

Then I received a great reply with the actual probable answer; all of these pins connected to the matrix are also connected to “pull-up” resistors. Before this project & reply, I had never even heard of pull-up or pull-down resistors, logic states, or any of that. But basically, the reason this hadn’t worked previously, is because this pin should be  “active-high”, and needs to be connected to VCC via a 4.7k resistor like all of its neighboring pins to work properly.

Well, sadly, I tried this and still, no results. So at this point, ive decided to throw in the towel. It’s possible that even with the probably-correct solution in front of me, I still managed to wire it up incorrectly, and that’s why this didn’t work. It’s also possible that there was simply a software change on this chip between the PSS-80 & the PSS-125, and no amount of fiddling will ever unlock this drum pad ive spent so much time chasing. Honestly, who knows? Maybe someone will come along and succeed where i’ve failed one day, but for now, the PSS-80 remains drumpad-less.

Except… There actually IS a drum pad on the PSS-80, though its not super practical to use. By booting into its secret test mode (holding 2 highest keys while powering on), you not only reroute all of the face buttons to the keyboard, but you also turn the “voice select” buttons into a real, working drum pad.

The only issue; Because all of the buttons are rerouted, all of the keyboards usual functions are disabled with test mode enabled. And they stay disabled, until you turn the machine off and back on again, disabling the drum pad. Ive done lots of experimenting with this test mode to try to unlock aspects of it in normal boot up mode (it also has a cool reverb voice only accessible during normal operation) and re-route these drum buttons, but I haven’t had any luck there either.

Funny how a functioning drum pad on this device always seems to be so tantalizingly close in so many ways, but also completely unachievable 😭

Anyway. Thats where I leave this project. Maybe someone will pick up this torch some day and continue on, but for me, it’s the end of the road ✌🏼

Hey, i got an old TS 305, and i would like to mod it a bit.
I am pretty new to circuit bending, and was wondering if you can give any tipps on what to look for, directions on where to find what?
mainly i'd be happy to start by adding decay or something.

Am thankfull for any tipps you might wanna spare!

Thanks for the input. Might be bad design also since there are units out there which act this way.
I could ask the previous owner of course, if it ever worked on this one, but he hasn't replied to my mail when I asked about the adapter.
I've also read that the different units may sound different when compared side by side, but that's no problem for me.
But I guess I can do without distortion or use a pedal if needed, unless of course somebody figures this out, I'm not much of an electrician myself and don't really know where to start poking.

I concluded that it's just a bad design and not a fault with my unit.
I noticed the same problem in that YouTube video as well.
It varies a bit so in your unit might be more noticeable than mine and so on but now there are at least three with the same problem which seems weird.
I really don't remember if it ever worked right so I left it at that.
It actually gets better ( you can hear the distorted signal but it's a lot less louder than the original) by replacing a 4053 but don't remember which one as it's been some time, in my case I couldn't hear the distorted signal at all.
At best I don't think you're going to get more than half the pot's travel after the unaffected signal cuts off so either way a bad design regardless if just fails in the field or if it's actually supposed to work this way.
Really hope somebody proves me wrong..

Reviving this thread once again.
New user; first post and seeking for help with my MB33 II.
I have a strange issue with main OUT volume dropping as soon as I turn the distortion pot CW.
The volume drops a LOT as soon as I engage the pot and then goes to zero about 1/3 of the distortion pot's travel.
As I understand from the schematic there's some passive current mixing going on before the signal hits the main OUT opamp which seems like it's only a I-V converter from the sumed current  leaving the OTAs.
So far do good but I don't see any good enough reason for the volume to rapidly drop as soon as the pot is turned.
I get just a little bit of distortion before the signal vanishes.
I have a hunch that it's probably a DC bias issue at play which manages to collapse the whole 13700 but I could be wrong of course.
I haven't actually had a proper look on the circuit but thought to post here in case anyone might have any suggestions.
Possibly help others as well..
Cheers.

Hello, new user here! Just found an adapter for my MB33 MKII and have the exact same problem, anybody have a solution or suggestions for this?
Here's a video demonstration I found where you can see how it affects the volume and sound:
https://youtu.be/fP7cjYmCjUQ?t=350

Thank you in advance!

Hey guys. First time poster here. I tried asking about this on Reddit a few days ago but didn’t get much of a response, so I’m hoping someone here might be able to help 🙃

So lately i’ve been modding a Yamaha PSS-80. Recently I discovered that it likely contains an unused drum pad, which i’d like to wire up with some push buttons, but I cant for the life of me get it to work.

So a while ago I ordered a service manual for the PSS-80 on ebay, and while looking at the circuit diagram I noticed an unused pin on the main IC (shown here, highlighted in red).

I compared this diagram to a diagram of the Yamaha PSS-125 (which has the exact same hardware internals as the PSS-80). The 125 has a drum pad, and upon further inspection I noticed that the unused pin on my PSS-80 is the same pin that controls the drum pad on the 125 (diagram shown here, pin and drum pad highlighted in red. Note the extra “SB5” column with the drum sounds in the bottom right).

Now, the first thing I thought of when I noticed this was the Casio SA-2. It also has unused pins and an “older brother” keyboard (the Casio SA-8)that it shares the same internal hardware with, where these pins are active. And people have in fact managed to unlock the missing drum pad on the SA-2. Heres a schematic of someone doing just that.

Now my question for those who know a little more about electronics and circuits than I do; Does this even seem possible? I haven’t had any luck yet, but here’s what Ive tried so far:

I first tried connecting pin B5 to pin C1 & C2, which looks to be how the kick & snare are triggered on the PSS-125 based on the diagram. This didnt work, and seemed to trigger all of the keys at once. This is when I realized that this pin was grounded on the PSS-80, and that all of the grounded pins had this “all keys at once” effect. So I cut the trace connecting it to ground and tried again. The multi-key sound stopped, but still no drums. Then I realized that all of the sound-select pins pass through a 47k resistor array before connecting to the button matrix, so I tried doing the same with pin B5. Still nothing.

Im about out of ideas. Anyone here done anything similar to a Yamaha keyboard? Anyone see anything obvious that im missing here? Any help with this would be appreciated

Hi guys

I am new to bending and the whole world of electronics in general and trying out a few SA-1s, following some of the great diagrams and tips here. Haven't had much luck yet, and just wanted to see if there were any general tips on how to diagnose problems. I appear to have killed one and the other two were bought 'untested and as seen'. I can get a few notes out of one before it, almost literally, coughs, chokes and dies. I can keep doing this by turning it off and on again, though it won't do it every time, but I can't get it to play more than a few notes. I haven't added any mods except add a line-out jack and battery pack. It doesn't look that great inside, and the battery coil is rusty.

Also, after the keys stop working, I can get various low hums and crackles by touching screwdrivers on the chip pins corresponding to glitch and other bends seen in the diagrams, so it's clearly still live and responsive in some way, but not providing any of the wonderful madness I got from the same glitch connections on the other one before it stopped working, so I don't know what the problem is with this one.

As I said, I'm trying to learn how everything works from scratch, so any suggestions for trouble shooting, much appreciated.

Cheers

For a future Google searcher:

It turns out the problem was cold solder joints on the YM3419B chip.  I was about half-way through recapping the whole thing, and that didn't make any difference.

I reflowed solder around the whole chip and that was enough to fix it for good.