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@ctt956- Thank you. Unfortunately, the electronics repair guy said he couldn't fix it. He said it was beyond his ability. So... I may not have any choice but to give up on it for now. If it's beyond his ability, it's unquestionably beyond my ability as well. Bummer.. Hopefully I will get lucky and come across a PT-30 or another PT-31 eventually. They don't seem to show up very often and I think buying it off eBay is way too expensive these days (especially after shipping and import taxes) Anyway, thank you all for the responses. I'll keep this thing around and hopefully figure out the problem someday.

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

@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?

An update for anyone who is interested: Some of my bandmates recommended a Thai guy who fixes electronics locally and they had some good results. I messaged him and dropped off the keyboard. I get the idea that he doesn't specialize in more complicated electronics, but I have no idea. He has repaired all kinds of appliances and guitar amp stuff. Now I'm just waiting for an update. Let's see if I get lucky.. Maybe it will be a cheap, quick fix that I couldn't identify myself. Or maybe he will tell me that this thing is hopeless and he can't help me. I gave him the little 2k trim pots I bought and I mentioned that I'm not sure if it's the correct part. I'm not sure he knows either. Pray for my poor little junker Casio. I really like this thing for some reason, so I'm hoping it can be brought back to life haha..

@CYBERYOGI =CO=Windler - Thank you so much for clarifying the meaning of the "B" that is printed on the board! That makes a lot of sense to me now. Ok, so we know for sure that it's 4.7k for the PT-30/31 models? It's definitely the same as the PT-80, which is what we got pictures of? That's where we got the whole 4.7k idea from originally. I assume a lot of the parts are the same. I just want to be 100% certain before I put the time in to installing either of the parts and find out it's wrong. I saw a PT-30 for sale today on FB Marketplace but it had a broken screen. It sold shortly after I looked at it. I'm not sure if I should be kicking myself for not buying it.. but it was a little beat up, and the seller wanted $20 for it. I already sunk $9 into my broken PT-31 (which I had falsely been told had a working screen and powered on) so if I sink another $20, I'm basically at $30 for no guarantee. It's not a lot of money really.. but I don't know if I would be capable of transplanting the screen from the PT-31 with that delicately thin ribbon cable, or if the PT-31's screen is even still functional as a separate part. Argh.. I guess the waiting game continues. Honestly, if I find a working PT-30 and the case is not perfect, I will consider transplanting everything into the PT-31 case because I really love the way it looks. Is that a really absurd idea? Haha. What am I doing with my life.. T_T

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.

I should have the little trim pot piece in a couple days or so and I'm about to start my vacation time finally. But.. I'm not sure if I got the wrong value potentiometer. I ordered 2k because I saw "2.2KB" printed on the board in that part's place, but I never learned what the "B" in "KB" is for.. I can't find an answer on the internet. Does anyone know? Is it possible the PT80 uses a different value for the resistance of its tuning trim pot or do I need to order and wait again? I don't want to go through the trouble of soldering this thing in to find out it's the wrong part and it won't function correctly but I don't know where to get a solid answer on this since no one seems to have clear pictures of the inside of a PT-30 or 31 or the service manual. I get the idea that it's better to have a pot with higher resistance than one with lower resistance if the exact measurement can't be found. I don't see anywhere to get the 2.2k rated pot, but I did find a 4.7k, which is strange because all the other options are rounded to the nearest hundredth or thousandth place (ex: 1k, 5k, 10k, 100k, etc.) Thanks in advance if anyone has an answer for this. It would save me some time. I'm not sure if this is a lost cause. Originally, I wanted to earn the pride of fixing it myself, but lately, I just want to hand it over to someone else and pay a bit of money to fix it or find out if it's even possible to fix it, because I have no idea what's wrong with it.. but I have no idea who to take it to. I imagine vintage toy keyboard repair people are pretty rare, and in Thailand no less, it's even more of a challenge with the language. I know electronics are quite similar across many different types of devices so maybe it's possible to find someone.. but I feel like I'm going to get weird looks taking a dinky little toy thing into a computer repair specialist. What do you guys think? For now, I am going to wait for a confident answer on the potentiometer (even though that probably won't fix the fact that it doesn't power on at all) and work on a side project. I'm going to add an output jack to another keyboard (my Yamaha PSS-100) and start planning out the isolated output mods on my MT-68. I have already fallen in love with my new MT-65, so the 68 is definitely becoming the lab rat. I'll make a separate post about that soon if anyone wants to follow along and help with my newbie questions.

@CYBERYOGI =CO=Windler - I will probably have to stay away from that mod because I don't understand what kind of switch can do that or where to connect it. That's ok. Maybe it's not my place to dig into that level of electronics. I want to someday, but I feel like I would likely get in over my head very quickly if I were to even attempt the first steps. I will remember you for future modification explorations. For now, I think I will stick to the easier modifications. @Chas- Ah.. it's too bad I already ordered a different part. I don't know if the part is the same between the 2 models anyway.. I wasn't sure when I would get a response so I ordered a 2k pot to expedite the shipping process. I saw 2.2kb printed on the board in that spot so I went with the best guess I could figure. It's odd that it says "kb" though.. Why doesn't it just say 2k? I feel like I'm missing something. What does the B stand for in 2.2kB? I'm clueless. At least it was only a dollar or so.. if it's not right, I just have a bag of useless doodads in a drawer I guess. Can anyone clarify the "kb" thing? @CYBERYOGI =CO=Windler - I don't doubt your expertise at all. But I do find it odd that the only destroyed parts I can find on this whole keyboard are exactly where someone would stick a screwdriver in. Why wouldn't any other parts have damage? I understand there is possibly damage I can't see.. but really.. Everything looks very clean and tidy except for those 2 exact spots. They are physically broken unlike anything else. There is no other physical damage at all. But I still don't doubt that it could be a combination of issues though.. Has anyone lost any hair from this stuff? Haha

@pianokeyjoe- Ahh.. I made a huge mistake! I was not looking at my keyboard when I posted my response. There's an arpeggiator on/off switch, but there is also a 4-way selector switch for different patterns when that switch is ON. I tend to respond to this thread in the late evening when I've already been exhausted by my daily work. That's my excuse for the moment.. but I feel a bit foolish too. Well.. I guess I have to brush that off and move forward with more focus. I appreciate your efforts to pull me back towards a basic understanding without shaming me, and I'm glad we have similar visions of what the ultimate "toy" keyboard should be. I think we both appreciate the auto-accompaniment options and the unique tones of these models. There's a special quality that nothing else seems able to create authentically. I look forward to the direction of this discussion as my time gets freed up over the coming month. For me, it's a slow process of trying to figure out the right questions to ask (when I have the time) and then trying to understand the answers, and then correctly executing the actions that achieve the goal. I don't have any updates for anything at the moment because it's a busy week. But I'm curious to hear about anyone's current project with modification, repair or dreaming up new things.

@pianokeyjoe- The extra arpeggio patterns are already active? I thought it was just an on/off switch with one standardized arpeggio pattern for each rhythm. It’s possible I’m misunderstanding the meaning of arpeggio 2 and 3 though. The more I think about it, the more I feel like the transpose option isn’t really important. It would be nice for “cheating” and staying on the white keys though. Admittedly, I’m not so great at playing keys. I mostly just use them to record one part at a time. Anyway, I am definitely not ready to go into more serious modding yet, but it’s interesting to start thinking about it. If it involves any soldering on the processor component, I will probably be too afraid to make a mistake. Those little leads coming off are too close together for me to feel any level of confidence on an irreplaceable part like that. The isolated multi-output mod will probably satisfy me. But I want to understand the arpeggio possibilities too.. Could there be more?

@CYBERYOGI =CO=Windler - I see there is also arpeggio 1 and 2 unlockable features. Would you just set a button for these also? If you don’t mind me asking, what would be the most ideal way to activate these features as a physical mechanism on the outside? I imagine individual slide switches.. but maybe that would interfere with the already-existing slide switch for (what I assume is) arpeggiator pattern 1.

@CYBERYOGI =CO=Windler - You make it sound like it's possibly a lot easier than I was expecting. I need to put a button somewhere that interacts with the chip to say the transpose function is temporarily "ON" while I press any key other than C and it will move everything relative to that? I wonder how you would activate transpose up vs transpose down though. Hmm.. (I am editing this afterward because I thought about it a bit more) I understand the concept, but actually physically executing this will take some time to understand I'm sure. I see this as a long term goal but it's nice to know that there's a path to it that doesn't sound too wild or dangerous. I appreciate the info

@CYBERYOGI =CO=Windler - Wow, that is super thorough info. Thank you. This will come in handy when I start to look into the possibilities of modding my MT-68 or 65. The 65 just came in today and it looks very good after I cleaned it up a bit. I guess that means the 68 will become a future mod project. That seems to make more sense. I think I only want to add isolated output jacks on the MT models since I imagine that would be a more simple mod. Having a transpose option would be really great though too, if it's not too complicated. I will have to research that for awhile. I wonder what the best type of part would be for rotating through the levels of transposition so the processor understands clearly. That's a question for later.. I better focus on what I can do for now. I think my first projects will just be to fix the PT-31 and the MT-400v. I'm just waiting for the 2k trim pot to come in for the PT-31 and I think I will open up the 400v further during my December vacation and continue on that thread again with my findings. Thank you so much for the continued interest. Your responses make this journey a lot more exciting.

@pianokeyjoe- I’ve had dreams about finding musical treasure like that. I wonder if this keyboard idea will come up in my dreams also. I’m a bass and guitar player mainly but I’ve recently gotten hooked on these little toy-like keyboards and I can’t stop thinking about them. It seems the general rule for these things for me to like them is that they have to be from the early 80s or they don’t seem very cool. I can’t understand why on earth Casio stopped continuing the evolution with their early vision. The auto-accompaniment, arpeggiator, analog drums, etc.. They had an amazing thing started. Anyway, my white MT-65 should arrive today. I hope when I open the case, I will suddenly become obsessed with the white models. The white PT-30 is a lot easier to find and I can keep my grey models for modification projects. Can’t wait! Has anyone done an isolated output for each instrument kind of mod yet? Curious to hear how that turned out if anyone has done it. For me, this would be the best thing to do. That arpeggiator would be killer if it could be separated and run through effects like tremolo, delay, long reverb, chorus, etc. The isolated bass would be amazing isolated through a synth bass octave pedal to get a fatter dub sound. Drool.. I don’t want to get too off topic here, but has anyone tried the Yamaha MK-100? That’s the model that got me started. I bought it on a whim and research of similar keyboards has led me to all these great Casio models. Could be a fun one if anyone wants to explore a different brand. The drums and accompaniment styles are not as good, in my opinion, but it adds some very unique features that I haven’t seen anywhere else.

@CYBERYOGI =CO=Windler - Nice detailed info. I really appreciate that. So there’s no cross-over between the MT-65 capabilities and the Super Drums variable patterns? Bummer.. Too bad the MT-65 stuff didn’t get developed further and physically downsized. It would be the ultimate casual home keyboard to this day. I think a lot of modern stuff adds too many bells and whistles. I want a PT-30 + MT-65 + added 400v functions in a tiny package. Oh well.. guess I just have to appreciate what’s already there.