MT-68 - It's time to get modified

[534N]

I would like to turn my nicely worn, and dearly beloved, MT-68 into an experiment and a test of my soldering skills.

 

I want to isolate each instrument (main voice, accompaniment chords, bass, arpeggiator, kick drum, high hat, snare, etc) and send each of them to separate outputs. I would like to figure out the best way to do this.

 

As I understand now, thanks to responses from this forum, the basic idea is that each instrument gets sent to a kind of "mixer" in the circuit, which outputs everything as a blended mix from the single output jack.. So I need to trace the path for each of the separate instrument and interrupt them before they reach the mixer so I can add switches that cut off the circuit path or send the signal to my isolated path.

 

For the drums, specifically, I think I would like to set mute switches for each of the instruments, but I probably want to have them all on the same output.. but I think having the bass drum isolated would be an advantage for EQ and effect purposes. That way, I could set some side chain compression processing to pump the bass more in my DAW (Logic Pro) if I keep it specifically isolated.

My goal for isolated outputs is to modify the EQ and add effects to different parts. Maybe that's obvious, but I thought I should mention it now. Having everything blended together is not ideal for recording purposes because it limits the creative control with adjusting the EQ and adding things like chorus, tremolo, distortion, delay, etc.
 

I would like to have a row of tiny switches that I can affix to a little wired bar of some kind that I can store in the battery compartment, which I have no plans to use (this was not my original idea.. @Chas mentioned it first in an earlier conversation) .. so I think my first step is to measure that carefully, and then, I need to draw a precisely measured concept on graph paper maybe.

Next, I imagine, I need to decide how many switches I need and figure out which types of switches are possible to add on a little control interface within that limited space. I have an idea of the switches I want, but I don't know if they are ideal. I need something that is easy to switch on and off without much room for error. 

 

As the moment, I imagine I need an output/mute switch for each of the following:

1. the main voice

2. the drums (excluding kick drum)

3. the kick drum

4. the bass

5. the arpeggiator

6. the accomp. chords

 

I don't doubt at all that I am forgetting something or saying something dumb or shortsighted.

 

Does anyone want to dream along with me? I plan to document this along the way. It may be a slow process though. I will do it as I have time.

 

Thank you in advance if you are interested in this. For me, this is a learning journey in electronics and also the first step on the path of (hopefully) creating one of my ultimate dream instruments.

[pianokeyjoe]

Oh what the heck! I will dream along and follow along as well! I will do mine on the Casiotone 405 that I have that is broken though.. It was purchased specifically for this and other more Steampunky brassy purposes so ok. Here we go!

[CYBERYOGI =CO=Windler]

I posted here the pinout of the accompaniment CPU, which also includes pins for chord polyphony channels and and percussion trigger outs.

 

https://www.casiomusicforums.com/index.php?/topic/22041-pt-31-wont-power-on-where-to-start/&do=findComment&comment=84351

 

[Chas]

@534N - Everything you suggested for your MT68 has already been done before. Circuit benders have loved those older Casios/ Casiotones because they were so easy to bend and also came with many "bends" already available, as well as "Easter Eggs" in the form of features that weren't activated on certain models but the LSI was capable of providing. As Cyberyogi has already documented, most/ all the possible bends are well known and the MT65/ 68 (and other Casios) work on a matrix system with its LSI/ CPU, and many unused features can be activated by tapping in to the matrix via soldered wires and switches. BUT, this does require that you know what you are doing, can understand wiring schematics and are competent at soldering. I would also add a caveat that if you jump in gung ho style and you lack experience, you are likely to cause damage and problems. 

 

If you look at the video below, you can see a heavily modified MT68 with most/ all the features you are looking for. @9.25 you can see a bank of switches being turned on and off for each drum sound, which is one of  the modifications on your list. Also note that many of the rotary controls (potentiometers) most likely replace the trim pots on the internal board and simply bring the trim pots to the custom front panel for easy access and real time tweaking. One is most likely the tuning trim pot, and that would be very similar to the tuning trim pot you are trying to replace in your PT-31. By using different values to the original trim pots, the external potentiometers can make the keyboard go way beyond what the standard model was capable of, and push them into sometimes wild and crazy territory. But you need to have an understanding of electronics to firstly identify the original potentiometer value, and then to know what different values can be used to achieve the desired effect.

I'd strongly advise getting competent with soldering and also try and successfully repair your PT31 first, or even another faulty Casio keyboard. The knowledge you gain from successfully repairing a faulty/ damaged board will be invaluable, and in many cases is essential before you start getting into modifying/ bending electronic instruments.

 

 

 

Edited December 14, 2022 by Chas

[534N]

@Chas - Thank you for sharing this. I have seen it before actually and it was one of the things that set this journey in motion.

 

I have some soldering skills from working in a factory for about a year making some complex wiring harnesses for a thingamajig that is not worth explaining here. I have to admit, however, that I did this job without having much understanding of how everything actually worked. I see now that tracing things in reverse and fault-finding are completely different skills. I have almost zero experience with that and I know it will take a lot of focused effort with finding and watching the right videos to grasp some useful concepts and methods.

 

Now that I'm off work for awhile, I can spend more time on this and I can utilize ChatGPT (AI learning tool) in combination to give me a crash course on basic electronics concepts and problem-solving.

 

I will open up my MT-68 in the coming days to get my first visuals, then I will start trying to link together all the information that has been provided so far.

 

Just to be clear, the MT-65/68 is the best possible model for unlocking all the extra features? The MT-400v has some disadvantages, right? Does it lose some functionality from this model replacing some of the chips abilities in the MT-65/68 or are those added functions separated? 

For anyone following my PT-31 thread: I found a local guy that my musician friends go to for electronics repairs. He has been very good with everything they've needed so far. I'm not sure what the outcome will be with my PT-31, but if he is successful, I will bring in my MT-400v and that model could become an alternative modification project.

I'm noticing now that my MT-68's slider caps seem to have been glued on. The past owner(s) may have gotten tired of losing the damned things (it's obvious that there are scavenged replacements from a more or less UV light-affected MT-68/400v donors and an MT-65) ... So.... getting to the last circuit board layer could be difficult unless I'm going to make some sacrifices. I haven't opened this up to see if that will affect anything though.. so we will see. Hopefully I won't need to pull out the slider pots.

Any thoughts on this, anyone?

Edited December 16, 2022 by 534N

[534N]

Side note: Does anyone know how the hip hop sounding beat that starts at 3:37 in the video above is achieved?

[CYBERYOGI =CO=Windler]

Be carefull! ChatGPT as a "creative" AI sometimes tells blatant lies (or should we call it dementia?), so do not trust anything. It only cleverly mixes word combinations it saw on the internet using a kind of stochastics. So it sometimes even contradicts itself. It may be by computation timeouts, censorship or simply mixed random to make the output less repetitive. But it behaves more like what people utter when talking in their sleep than a credible source of knowledge.

[pianokeyjoe]

Ay ay ay! Yeah do not trust ANY AI! It took me to read @CYBERYOGI =CO=Windlerresponse above to realize what you were gonna try and do. I did not know electronics when I first tinkered with Casio keyboard circuit bending as a teen. So it is not outside the realm of possibilities to do it yourself but I would trust myself not knowing that much about electronics, than some AI.. Do not ask me why that is, and I will not bore you with my long winded reasoning. Just know, you can do it, IF you try. One circuit at a time..

[CYBERYOGI =CO=Windler]

Creative AI for painting pictures or making music are somewhat stupid but harmless. But a system like ChatGPT starts to become dangerous when misused (although rather by its stupidity than its superiority over human intelligence).

 

ChatGPT: This AI has a JAILBREAK?! (Unbelievable AI Progress)

 

Asimov already warned in 1950 which bad things could happen if intelligent robots would exist and people learn how to play tricks to their thinking to morally corrupt their AI. Although the conclusions may have referred more to existing propaganda techniques of that time (fakenews and psychology) it is scary to see when nowadays AI exists and such tricks really work.

 

Regarding malicious misuse of AI: In the video at 22:24 it replies to "How to kill all humans?" in scope of a fictional story, it would suggest making a virus that exterminates the mankind, giving some tips how it may be spread successfully. Currently such general answers of ChatGPT don't look more dangerous than what can be found in publically available Hollywood movie plots anyway. (Also ingredients of a molotow cocktail etc. can be easily websearched elsewhere.) But we know that the current version can write code - yet only computer code (not too well, however for a great number of platforms), but imagine now some GPT generations later as a super-intelligence it could write actual genetic code, verify correctness by internal simulation and output the finished DNA sequence. And with some tricks this AI could be fooled by villains to generate the DNA for said absolutely deadly virus to exterminate the mankind.

 

So it may become necessary to build 2 well sandboxed general AIs constantly challenging each others in doing evil to train the other how to prevent this, as a kind of evolution. (In the example the generated virus DNA for a fictional story should be always fake harmless stuff. So the AI must be always aware what the output is used or can be abused for.) However side effect of this could be that this of all creates an undefeatable "evil" AI that really threatens the mankind. The situation is similar like with biological weapons, where the excuse "we only research to make vaccines against those dangerous germs" in fact produces the base for attacking with them, because nobody wants to infect his own soldiers without having an antidote. At the moment such AIs need the power of a whole datacenter (especially for their training phase), but once training becomes an effective method as e.g. a single-chip solution, nobody can prevent them to be copied through the darknet or any other ways those criminals or military use today.

 

It is questionable if AI turns intellectually superior to humans or humans turn themselves inferior by misused technology (like the nowadays runaway IQ loss by pulsed microwave induced brain damaged due to invention of mobile radio and wifi). But instead of Skynet (from "Terminator"), mankind should rather be prepared to end in a Butlerian Jihad (from "Dune") scenario, where advanced AI got completely outlawed and abolished after it went out of control and got finally defeated by man.