PT-31 - won't power on.. Where to start?

[534N]

I found a roughed up PT-31 (black version of the PT-30) on FB Marketplace for dirt cheap so I decided to take a small risk. The guy I bought it from said it was able to power up and he said the screen worked, but he either outright lied to make the sale or he misunderstood from the language barrier (I live in Thailand). Either way, I have a useless paperweight for the moment. I tried to plug in my official 7.5v Casio center-negative adapter into it by the way, so I don't think improper power supply is the issue. We can probably rule that out.

 

I wanted to see what the most common issues are for this situation. Is there a logical step-by-step problem-solving sequence I can go through to figure out the issue? Are there any definite signs of "no hope" that I can look out for before getting too invested? I noticed the battery compartment (which is missing the cover) has some crusty junk in it, which I assume is the remnant of some bad batteries, but when I opened the unit up, I didn't see that there was any leakage at all on the circuit boards.

 

I can tell someone else has already opened it up because the foam stuff has disintegrated inside and some tape has been undone. I'm going to clean that up with alcohol as soon as I can. Also, the LCD screen is crooked inside.. I hope it's not damaged because that's the main reason I really wanted this model vs the PT-20.

Side note: There is another missing component from the underside. There's a second compartment that (as I understand) was supposed to hold some kind of tape-memory apparatus for storing sequences or something. I don't care about that at all because I would never use it anyway, but I'm hoping it doesn't affect the basic functionality.

 

I'm going to include some pictures. Please tell me if it looks like this thing is worth the time. I'm only out $9 if this fails so it's not a huge deal and I will keep it for parts in case I find a functional one that is missing something, but I really love this black version and I would love to earn the pride of fixing it myself. There's something beautiful about an instrument that shows a rough history so I want to rescue this thing.

 

Thank you in advance for your time!

 

Edited November 22, 2022 by 534N

[pianokeyjoe]

Well sir, YOU used the correct power adapter, but does not mean the seller did. I see some like mildew or water spots on the board? You check close at the power jack solder points that they are not cracked? Sometimes the solder looks fine but you can barely see that the points lift up from the board and there is a fine crack between the solder point and the copper circuit trace when you wiggle the jack slowly. Seeing as you did take this apart and took good pics, I do not really SEE any components that are Sploted but hmm, a stumper this one is. My PT20 had the aformentioned loose jack issue and I fixed that only to find the unit has logic board issues too.

[pianokeyjoe]

Zoom in on the image I reuploaded here and scratch away carefully the green tint until you see copper on the trace where the circle is and resolder that point until you get solder on the copper and jack solder point. I think there is a crack under that point and the brown flux there. I could be wrong but that is where I have had to fix MANY a Keyboard.. MANY.. The other is tap power direct to the points with a 9VDC PSU or battery. Also try direct tapping at the red and black power points for the battery compartment. I think that may be relevant.

[534N]

@pianokeyjoe- Thank you for the fast reply. I will try the things you've recommended.

 

Sorry if this is a total newbie question, but.. Is it safe to test the power with a 9v battery if it's made for 7.5 volts? I don't question your knowledge because I remember you said you've been doing this for a very long time. Just want to make sure there's not a slight overlook on that detail.

 

Also, I totally agree that a previous owner may have used an incorrect power supply somewhere along the life of this thing. I didn't rule that out at all. I only meant that I ruled out that the unit not powering on was not because of MY mistake with the power supply (to my knowledge).

 

Anyway, I really hope nothing irreplaceable has been fried. Even the replaceable stuff will be difficult for me to find with my limited knowledge of this stuff so far. The only project I've completed so far was a guitar pedal mod and I just followed exact instructions from an internet forum without fully understanding what I was doing with each component. Fortunately, people on the internet who nerd out about this stuff tend to be very passionate and honest.

 

I just realized from trying to watch a PT-30 teardown/rebuild that the PT-31 is made differently! It's not just a different color.. the circuit boards are not the same. I was hoping that PT-30 video would help me out with step-by-step visual instructions and understanding, but it looks like it may not be a perfect match. The PT-31 has a smaller green circuit board for some reason.. or someone was a total ninja nerd and cut off a huge chunk with absolutely zero trace of having done so. I'm intrigued.. What the...

 

 

Edited November 22, 2022 by 534N

[534N]

Just to show that I'm not crazy.. They are totally not the same!

 

 

(starting at the 4:53 mark and compare with my PT-31 picture)

 

[pianokeyjoe]

Yes sir, 9VDC is fine for temporary checks. Hmm wow! Yeah that IS different! PT30 vs PT31! But the power supply input logic IS the same. I venture to say if my fix does not fix it, the issue could be the input capacitor(big electrolytic near the power input jack), or the voltage regulator(3 pin with metal tab thing also near the power input jack.

[pianokeyjoe]

Lol! Funny, you did not take a picture of the area where the power jack is, on the brown component side. Just barely got to that side in the camera view. I can not see those caps to see if they are bulging or leaking or the other components to see signs of distress. Could you please take a shot of the power circuits side please?

[534N]

@pianokeyjoe- Good to know about the 9v testing. Thanks.

 

I will try to get a closer picture when I re-open the keyboard today. This is my first time actually unscrewing circuit boards in a device. I used to be really scared of it in the past because I thought touching electronic components could mess something up (like scratching a vinyl record for example). These forums and all the detailed cleaning and repair videos on YouTube have helped me realize that it's actually not that scary. I am, however, concerned about that thin LCD cable. I imagine it can only handle so much bending before it loses its functionality and I'm certain I could never replace that. Also, these things have a million little screws and I find that it's easy to forget where they go in the re-assembly process. It seems that 2 sizes are standard though. I started writing S next to all the holes that need a Small screw and an X where other screws go. It's nearly making my eyes go cross. I suppose I need to make a video so I can backtrack if it gets too hairy. I decided to start with this (seemingly) more simple project before making an attempt at fixing my MT-400v (which you saw in another recent post).

 

I'm not sure if anyone will know the answer to this, but.. the tape memory circuit board seems to be stuck to the case and it's soldered to some short wires that prevent me from pulling the boards completely out. This is putting some uncomfortable pressure on the thin LCD ribbon when I'm trying to get in and do stuff. Can I just cut that bit out without hurting the overall keyboard since I don't plan to ever use that function anyway? It's probably a dumb question, but I want to ask before I make any assumptions and brick this thing even more than it currently is. I'm thinking I want to use that compartment for some future addition, like a power supply holder (is it possible to get 7.5v from some USB rechargeable battery bank?) or a multi-output option (to separate the bass, drums, arpeggiator, main tone, etc) that can tuck inside for easy storage.

 

I know I'm getting way ahead of myself since I don't even know if this is salvageable yet, but it's fun to dream. I really love the look and feel of this keyboard. I can't explain what it is, but for me, it's reminiscent of the super 80's He-Man days, with all the chrome letters, laser cannons on dinosaurs and muscle cars with GI Joes. I think I may leave the keys in their unusually aged color so it looks like a piece of ancient salvaged tech from some future post-apocalyptic world.

 

Anyway, I've rambled a lot. I guess my passion for this stuff is really started to explode. If I can fix this thing, I'm quite sure I will become a regular on this forum because the addiction will definitely solidify. Thanks again for all the tips!!

Edited November 23, 2022 by 534N

[534N]

@pianokeyjoe - I'm not sure these pictures are good enough to see anything useful, but here is what you requested (I think?)

 

I tried batteries today. Still no luck with powering the unit on.  

 

I saw in the teardown YouTube video of the PT-30 (posted above) that the guy pointed out that the power switch mechanism with its cheap graphite tracks are a likely point of failure in the circuit. I'm hoping that's all it is and maybe I can just draw on there with a pencil to get the electrical current running through again. That would be such a lovely fix if it's just that. I fear it's going to be some kind of damage to a component that is nearly impossible to trace or replace.

 

How often has that happened to a keyboard in your experience? (Not being able to fix because the damage was too severe?)

[534N]

@pianokeyjoe - Upon closer inspection, I have discovered some unusual things..

 

First, some of the capacitors and transistors seem to have a yellow glue-like substance that sticks them to the board, but it's not consistent with all of them. I wonder if that was intentional or if it's residue from overheating components.

 

Second, I noticed that a trim pot type component (that should be accessible through the tuning hole on the underside) is missing but it's there on the PT-30 video. If I look close, it appears that something may have been there in the past and was either removed or fell off... I have no idea. Or maybe this model, being so different from the PT-30 already, just didn't include that, even though the bottom of the case has a hole and instructs the user to tune the keyboard by turning something.

 

I wonder.. why wouldn't that be there? That seems to be really important.. How could it have been forgotten, fallen off or why would it have been removed by someone? I'm a little bit annoyed at the possible answers to any of these questions, but I hope it was just not part of this design. But if that's the case, there's no guarantee that it will stay in tune with any other music I write.

 

I wonder also.. can this keyboard even function without that trim pot component?

 

Pictures below for comparison. I took a picture from the PT-30 teardown video and then a picture of my PT-31. 

 

I'm thinking maybe some idiot went psychotic with a screwdriver and broke off the piece inside and the next person in line probably removed that lose piece from the case. Please tell me I could be wrong. $#*%!!!

 

[534N]

@pianokeyjoe- I opened up underneath that spot and I am 90% sure that the trim pot was broken off. There's solder on the other side in the 3 places that the component would go through. It only makes sense. Also, I see that a tiny bit of plastic is chipped off around the tuning hole on the underside of the case. All the evidence points to negligence. I am trying not to get angry about it because this is all a learning process. Just annoyed that it couldn't just be a simple fix.

 

My question now is - Can I replace this component easily or am I better off just keeping this junker for parts if I can get lucky enough to find another PT-31?

 

Sigh.. T_T

[534N]

I decided I'm not going to give up just yet. I think this is a valuable learning opportunity and I need to accept that I may not get the outcome I want in the end, but I will definitely gain some knowledge from trial and error.

 

I see that the circuit board is labelled 2.2kb.. does this translate to 2.2k ohms? I have found a part that appears to be similar to the one in the PT-30 video. I feel like I'm Sherlock Holmes right now and it's ridiculous.. but I hope I'm on a hot trail with this.

 

I am guessing maybe the 2k version of THIS is what I need as a replacement. I could solder it in place of the missing original. It has the same 3-point triangular arrangement.. but is 2k the same as 2.2kb? I can't be sure I'm fully understanding that part.

 

Even if I fix this bit, I'm not sure if it fixes the power issue. It may not even be related.

 

Side note: The sliders on this PT-31 feel very smooth with their movement. I don't get the idea that they have failed based on feel. Of course, someone could have cleaned and lubed them already with the same hopes I have now. For contrast, my MT-400v's sliders feel quite rough and I get the idea they have been through some abuse, either by the environment, past use, or both combined.

 

I feel like I've rambled too much.

 

@pianokeyjoe- Could you tell me about one of your most difficult - but successful - fixes? I need some hope haha

[Chas]

I can try and help you with some of these questions:

 

 

5 hours ago, 534N said:

First, some of the capacitors and transistors seem to have a yellow glue-like substance that sticks them to the board, but it's not consistent with all of them. I wonder if that was intentional or if it's residue from overheating components.

 

 

It's almost certainly intentional. It is likely a type of glue use to hold the components in place, especially the larger capacitors, and it is used to stop them from moving about. However, if the large capacitors show signs of bulging and/ or splitting, then it could be gunk from a dying capacitor. But the fact that other components also have signs of this glue as well suggests that it is indeed intentional, more so if the glue is specifically under individual components rather than randomly over the board or located in a localised area near a suspect capacitor. 

 

5 hours ago, 534N said:

Second, I noticed that a trim pot type component (that should be accessible through the tuning hole on the underside) is missing but it's there on the PT-30 video. If I look close, it appears that something may have been there in the past and was either removed or fell off... I have no idea. Or maybe this model, being so different from the PT-30 already, just didn't include that, even though the bottom of the case has a hole and instructs the user to tune the keyboard by turning something.

 

I wonder.. why wouldn't that be there? That seems to be really important.. How could it have been forgotten, fallen off or why would it have been removed by someone? I'm a little bit annoyed at the possible answers to any of these questions, but I hope it was just not part of this design. But if that's the case, there's no guarantee that it will stay in tune with any other music I write.

 

I wonder also.. can this keyboard even function without that trim pot component?

 

 

That looks most likely to be where the tuning trim pot should be. A few years back I bought a PT-80 needing repair, a model from around the same era as the PT30/ 31 and similar(ish) in design. It had an access hole on its underside for the trim pot, and someone had been bashing something in that hole and damaged the trim pot on the circuit board. I identified the damaged component, purchase a similar trim pot with the same rating, and swapped it over for the damaged trim pot. It was then all up and running again after that.

 

As to why it's not there on your PT31, likely someone has heavy handedly shoved something into that hole and broken it off, similar to what happened with my PT-80. If it's not rolling around inside the case, then there's a good chance your PT-31 has been opened at some point in the past and someone removed it.

 

And I think the keyboard will still work without it. I'm trying to remember how my PT-80 behaved before I repaired it, though I'm pretty sure it still turned on.

 

3 hours ago, 534N said:

I see that the circuit board is labelled 2.2kb.. does this translate to 2.2k ohms? I have found a part that appears to be similar to the one in the PT-30 video. I feel like I'm Sherlock Holmes right now and it's ridiculous.. but I hope I'm on a hot trail with this.

 

 

I think that is the case. My PT-80 still had the damaged trim pot in place, and I was able to identify the rating based in that. Or I might have read the circuit board screen print. I still have a bunch of the trim pots back home as they came in packs of 5. When I return home at the weekend I will dig them out and see what the rating is on them.

 

4 hours ago, 534N said:

My question now is - Can I replace this component easily or am I better off just keeping this junker for parts if I can get lucky enough to find another PT-31?

 

 

Yes, it's easy to replace with a little bit of careful soldering. IIRC, they're soldered on to the board at 3 points. You just have to be careful not to use too much heat and damage tracks/ lift the solder pads.

 

13 hours ago, 534N said:

I am, however, concerned about that thin LCD cable. I imagine it can only handle so much bending before it loses its functionality and I'm certain I could never replace that.

 

Definitely be very careful with those LCD ribbon cables, as yes, they are very easily damaged and very hard to repair. Early Casios are very well built but its often the ribbon cables that are the weakest link. Same applies to the early Casio calculators.

 

13 hours ago, 534N said:

I'm not sure if anyone will know the answer to this, but.. the tape memory circuit board seems to be stuck to the case and it's soldered to some short wires that prevent me from pulling the boards completely out. This is putting some uncomfortable pressure on the thin LCD ribbon when I'm trying to get in and do stuff. Can I just cut that bit out without hurting the overall keyboard since I don't plan to ever use that function anyway?

 

That might be possible, though rather than cutting wires I'd try and go the de-solder route. Generally the golden rule is not to do anything that can't be reversed. It looks like that tape memory circuit board is open circuit until the tape device is place on the connecting pins, so at quick glance you could probably just cut that part out of the circuit entirely without any noticeable effect other than not being able to use the tape load/ save feature. But without the service manual, it's not certain exactly how it's all connected, so be very careful if you do remove it from the circuit.

 

I've also tried to find a Service Manual but no luck. I did find a PT30 discussion on the Circuit Benders UK forum that confirms that the board in question is glued into place. There's also some interesting insight  of its construction that might also help you with your PT-31:

 

https://www.circuitbenders.co.uk/forum/index.php?topic=490.0

 

On 11/22/2022 at 12:12 PM, 534N said:

Anyway, I really hope nothing irreplaceable has been fried. Even the replaceable stuff will be difficult for me to find with my limited knowledge of this stuff so far. The only project I've completed so far was a guitar pedal mod and I just followed exact instructions from an internet forum without fully understanding what I was doing with each component. Fortunately, people on the internet who nerd out about this stuff tend to be very passionate and honest.

 

 

Most of the components that you see are general electronic parts that are still easy and dirt cheap to find - capacitors, resistors, diodes, transistors etc. The problems only come about when its one of the custom LSI chips or custom displays that have failed, because most of those are long since out of production.

 

As mentioned, I tried to find a Service Manual for both the PT-30 and PT-31 but to no avail. It's possible that there's another related model than shares much of the same circuitry that was used when servicing these models. 

 

If you haven't already seen it, Mr. Cyber Yogi has a lot of useful information about the PT30 (and related models) on his TableHooters website:

http://weltenschule.de/TableHooters/Casio_PT-30.html

 

I'd suggest just getting some power going into your PT and then use a multimeter to probe and check for voltages. Just a simple check of the power switch points could indicate whether that is what is causing the issue if you can determine that power is reaching the switch, and is/ is not leaving the switch when it is turned to the "on" position. If the switch is at fault and cannot be repaired, it is possible to bypass it entirely and have the keyboard permanently on, though I would advice trying to get a functioning switch to have things working as they should.

 

Do you have a voltage/ test multi meter? If not, grab hold of one as trying to go much further will be groping in the dark, plus they are very inexpensive for a basic model. With a test meter you will much more easily determine of voltages are reaching the various components and boards. Oh, and as I've mentioned in a previous topic, the brown board is likely the analogue rhythm section of the keyboard, and the green board is the melody and main controller section. That will help you to know what part you are examining/ investigating.

 

Keep up the investigation and let us know what you uncover. Hopefully it will be something simple and you can get your PT up and running again. 👍

Edited November 23, 2022 by Chas

[pianokeyjoe]

I agrees with @Chas, the tuning pot was removed but the unit would still turn on. The glue is normal. Look for browning on those resistors, and bulging on the tops of those electrolytic caps. You would need to test with the 9VDC on the battery cables again and then use the volt meter to test for voltage going into the keyboard around the PSU input jack. remember the jack has a built in switch that cuts off when you plug in the power supply to protect the batteries from back feed of power so if that switch inside the jack is broken, that will cause part of the problem too. The power switch is possibly NOT a separate device on this model but part of the Control panel itself.. yes, the panel with all the buttons and LCD(DOH!!!!). Like the video, you would need to desolder that little tape interface board but my understanding was you could unscrew the main board that has the PSU jack and flip that back towards the back (where the LCD film is),and then you would have access to the control panel underneath to remove it, along with the speaker, and then that whole stack of boards would have to folder over to the left of you towards the tape interface side like on the video. It is a pain but it is how it needs to be done. The LCD is trapped under the control panel with 2 screws on a plastic bezel inside. You would want to unscrew and free that sucker before undoing the control panel by carefully moving the main board towards you(away from the back only a little), not to pull the film too much. The film should be on the BOTTOM part of the LCD and not the top so you would have millimeters of working space but at least something lol. Too bad you are in Thailand and not USA or I could offer my repair service.

[pianokeyjoe]

you have to prop all those boards up from flipping over the case too much to stretch the lcd film. Seems you can then unscrew the control panel including the chord buttons section to your right.Then you can SEE, if there is a CRACK on the control panel or the switch section having traces missing or deteriorated.

[534N]

@Chas- I appreciate your responses to my questions!

 

It's nice to know the glue is kind of a standard thing. I don't see any components that look fried or broken but I'm not sure I would know what the tiny clues look like. I imagine they can be very subtle in many cases.

 

I need to do some detective work with a multi-meter but I'll be honest.. I don't know exactly how quite yet. I have one, but it's a bit of a mystery to me at this point. I once used it to check the resistance of some guitar pickups but I've even since forgotten how to do that. Some study will be required.. fortunately, I'm off work for the next week.

 

Anyway, your PT-80 worked without the tuning trim pot? I'm kind of surprised by that. I wonder how it chooses the tuning to stay at without that component telling it anything.. Or... maybe you still had the pot attached (albeit damaged) so it was still bridging that gap in the circuit to keep its functionality(?)  I would definitely love to hear about the pot you used. I want to pull the trigger on ordering it so it can get started on its long, slow journey from China. I haven't found the part in domestically for a reasonable price anywhere yet. I'm not sure where else I can go for such a specific thing, especially in Thailand, where lots of shops barely an internet presence or English names to search for.

 

Thank you for the website link. It looks like I can pry the tape memory board up from the inside of the case if I'm careful. This would help a lot with removing everything for easy-access testing and repairing.

 

@pianokeyjoe - Ahh.. you say the tuning pot wouldn't prevent powering on. Guess I'm back to square one on that then. I'm going to try to test with the multi-meter after I have a better understanding of that process from watching videos. I wish I could get the service of someone like you, especially if I could watch the process and learn. That would be amazing.

 

I appreciate the tips with how to manage the layers of boards. I think I've been fairly careful so far, but I don't know how much strain I've put on the LCD. If I get this thing working and the LCD doesn't work, I will be sad.

 

I will try to dig into this further in the next few days after I figure out how to correctly use my multi-meter and I'll see what I can uncover.

[534N]

I saw in the YouTube video (posted above) that the guy recommended using a graphite pen to fix things that use graphite traces. Can anyone recommend a product? I'm not completely sure what I'm looking for but I imagine he recommended the pen form of this because it's more gentle for applying graphite than a standard pencil. He said the power switch mechanism was very delicate so I want to find whatever he uses, if possible. I imagine it might be good to have for my MT-400v that has some inconsistent potentiometer issues also. Thanks in advance!

[Chas]

7 hours ago, 534N said:

@Chas

Anyway, your PT-80 worked without the tuning trim pot? I'm kind of surprised by that. I wonder how it chooses the tuning to stay at without that component telling it anything.. 

 

Quick response. 

 

A trim pot is simply a variable resistor. Without a circuit diagram, I am guessing that with my PT80  it simply gives a value to the LSI CPU to tell it where to set the base value for tuning.  The CPU probably starts out with a maximum value and subtracts the value it receives from the trim pot. Without a value from the trim pot, it will default to the maximum value.  Thus it would be possible for the PT80 to still work without the trim pot.

 

As said, this is at a guess because I don't have access to the schematics, so don't take this as gospel!

Edited November 25, 2022 by Chas

[534N]

So.. I was poking around a bit more and I realized there's no component inside where the reset button should be accessed through the hole in the back (see picture). I imagine whoever broke the tuning pot also went crazy poking around in that reset spot too. Maybe they thought stabbing and scraping around would bring the keyboard back to life. I have no idea what that part is supposed to be. Is it even replaceable? Does anyone know what it does functionally? Could that be the reason the keyboard doesn't turn on?

 

Does anyone out there have a service manual for this thing?

 

Also, @Chas - Sorry to bother about it again, but did you happen to find the type of pot that you used to replace your PT-80's faulty tuner? I imagine it's probably the same one. I want to order that part.

 

I am feeling a bit discouraged with this at the moment because it seems like finding the problem is nearly impossible with the limited understanding and resources I have right now. I'm watching a video of someone repairing a VL-1 to better understand the process of problem solving.

 

 

 

Does anyone have another useful video resource for visually learning how to repair the more simple keyboards like this? Thanks in advance.

[534N]

I decided to go a layer deeper to take a peek. I think this is the most beautiful circuit board I've ever seen, though I can't say I've seen many yet. I wanted to ask for opinions about the graphite power control switch. Does it look like there is not enough graphite on there? I really don't know anything about this except for the basic concept of graphite being conductive and being used to complete a circuit. I'm not sure how I should apply the graphite or how much I should put or exactly where. Do I cover each grey block completely or do I just trace the lines that are etched in?

 

Again, thanks in advance, if anyone can help with this.

 

 

[534N]

I did one kind of multimeter test to see if the PSU input jack made a full circuit connection and it seemed to be fine if I did it correctly (not confident on that). I have to be honest.. I don't fully understand all the functions of the multimeter yet. I haven't found a good video to explain all the settings clearly and I'm a little bit afraid to experiment if I could cause more damage. I did the beep check function that tests continuity (I think?) and it beeped when I put the leads on the in/out solder points of the PSU jack. That means I don't have cracks under the solder, right?

 

If so, I'm not sure what to do next. I didn't see any cracks on the power switch component with the graphite tracks in the picture I posted and I haven't seen any cracks on the circuit boards. I can't find any components that show visible signs of being damaged either.

 

My only concerns for the moment are :

1) the missing reset button component
2) the graphite traces on the power switch mechanism (is that considered a pot?)
3) the missing tuner trim pot, even though that apparently doesn't matter for powering on(?)

 

When I figure out the right parts to use for replacements, I will move forward with the next level of fault-finding. I'm tempted to take this to a random electronics repair person here in Thailand to see if they can just do it and tell me what the problem is so it's less effort, but I'm afraid the language barrier or a possible misunderstanding of some kind could make matters worse.

 

I'm hoping to learn more from this because I just found an MT-65 locally in excellent condition (with case) for pretty cheap and that means my MT-68 could become a future candidate for isolated output mods for each instrument. But I won't feel confident with that stuff until I conquer this first level of problem solving and understanding electronic components. I imagine I have a very long way to go with this. I've disassembled and reassembled this PT-31 at least 5 times now.

[pianokeyjoe]

A real stumper without it being in front of me sadly. The 2.2k pot you can buy and replace. The reset switch point is missing on BOTH models and is a design not a flaw. That switch would be nothing more than 2 pieces of metal that are soldered and do not make contact until you push in the metal strips together with a pin to short ram to ground to reset the keyboard(the PT50 would be the one to have this reset in place). So that is not an issue here. Since you checked the input jack and surrounding solder points, there is really nothing else I can suggest myself again, without the keyboard in front of me. I currently have a semi dead PT20.. I have not returned to fix it yet and it has a strange sound issue like it is not getting enough power and sounds like dying batteries kinda sound but the PT20 DID have input jack issues that I fixed first in order to then find out the keyboard still has issues. And your board is of the same electronics range ironically(PT20/30/31/Fisher radio boombox keyboard). If you have not fixed this by the time I attend to my PT20, and I can fix my PT20, I may have some insight to help your situation but for now, I am out of ideas. Now on that MT65, get it quick!! LOL! I do know even if the keyboard I buy may be dead, if the price is right, I can always try to fix or use the parts for another of the same model that may come my way again to fix for another issue(or I would hope at least ). Maybe some one else here has some insight I am overlooking too?

[pianokeyjoe]

Aaannd?! After seeing the VL1 video you posted the link of, I am now more informed on what I feared.. For both you.. and ME. The CPU is bad on your PT31 and on my PT20. I had a CZ101 that lit up all the leds and screen with blocks and no sound or change of such status when power switched off(stayed on). So the first thing is checking the battery compartment and input jack and area. Next the components and boards for battery acid residue or other signs of distress, and lastly.. checking the most commonly failure prone components if you can, and ... gulp, the CPU which is NOT easy to source or replace.. You sir may be in that portion of this ordeal. I may still have hope on the PT20 as it does power on and all functions work, just very low and very bad audio.. But my unit may be a broken pin on the IC chip so sigh.. there's that. I hope you can source another of these boards for cheap, but seems at least after seeing the video, this is the end. As for the MT400V, you have tons of hope left for that one lol! It mostly works

[534N]

@pianokeyjoe- I REALLY hope it's not the CPU. I know that would ruin all hope of bringing this thing back to life because there's no way I'm going to try to replace it or troubleshoot it by making a complex diagram like the guy in the video. That stuff is WAY out of my league right now and I doubt I will ever want to go that deep unless it's something super rare and valuable. It's a hell of a lot easier to just buy a new keyboard. I'm really attached to the PT-31 specifically though. I like that aged grey tone with the pink accents but this model is a lot more rare than the white PT-30 version. T_T

 

Anyway, about the reset button. There isn't even a little piece there. Something has been broken off, I'm quite sure. There should be a little moveable piece of some kind, right? That may not have any effect anyway, but it's all I can find so far.

 

I'm thinking MAYBE the power button graphite is too worn out to get good electrical contact.. I know there was a suggestion to modify the circuit to bypass that and keep it "always on" but I don't know how to do that quite yet and I'm afraid to ruin things more by making a mistake. It shouldn't hurt anything if I use a standard pencil to draw on some extra graphite, right?

 

I bought the MT-65 by the way. It's on the way. I wish this model existed in the form factor of the PT series stuff. There's such a special feeling of being able to pick a keyboard up effortlessly with one hand and take it anywhere without any second thought. With the bigger keyboards, I tend to hesitate with practicing because I know I need more space.

 

I know the MT-65/68/400v chip is in a few other keyboards. I never looked to see if it's in a PT sized one. If it is, I think that could be the ultimate modification project. Oh... more pipe dreams...

[CYBERYOGI =CO=Windler]

On my PT-30 the reset ("P") button is vital for operation! By a hardware bug, the PT-30 tends to crash (lockup) during battery insertion and will not respond to controls anymore. If this happens, switch it on and press the tiny "P" (reset) button at the case bottom with a pointed object to clear memory (erases sequencer contents). To avoid the crash, if the instrument was left without batteries for over a minute (which corrupts SRAM contents) always slide the mode switch into "play" position before inserting batteries or connecting a power supply. However your model is a different version that may use a capacitor for automatic reset (thats how it should be made) when inserting batteries.

Interesting is that your PT-31 has a different PCB layout with smaller analogue PCB. It looks like severely damaged by battery acid vapours, so chances are high that also the through-hole contacts on the PCB corroded away. If any copper traces have black spots under the green coating, they likely won't conduct anymore and need a wire soldered across to fix them. I patched together a severely battery damaged PT-50, which was a nightmare to repair because e.g. the chord button panel traces were completely corroded away. To a novice this is hopeless. See here what may await you:

 

 

When exposed to battery acid, there is also a high risk that the LCD or its foil cable has decomposed. (Do not scribe the foil with pencils etc. - any friction, folding or pulling will make it flake apart even worse! There is no simple fix, except installing a foam rubber strip (window insulation adhesive tape) to press the ends against the PCB and display glass if they came loose.)

 

But first replace the 2.2k tuning trimmer, else the CPU may get no clock frequency and can not run. That it came loose looks like result of battery acid.

 

The tape interface cartridge TA-1 was AFAIK an expensive optional luxury addon that is extremely rare now and surely never came pre-installed in any Casio keyboards.

 

Casio MT-65 chips have nothing common with PT-30/PT-31 and definitely can not be replaced with them.

Edited November 29, 2022 by CYBERYOGI =CO=Windler