help! Casiotone 403 Accompaniment Issue

[jorud]

hiiiiii!

 

i've just acquired a Casiotone 403 for 37 USD (hope i got a good deal on it) but it has an issue with the accompaniment section:

there seems to be a constant drone of a few notes, sounds to me like the first preset (piano). everything else seems to function normally though!

i opened it up and sprayed contact cleaner on certain areas (no idea what i'm doing) but nothing improved..

 

anyone happen to know how to fix this? i've provided a video below of what i'm talking about... much appreciated thank you for reading 🤠

 

 

Edited September 20, 2021 by jorud

[pianokeyjoe]

That sounds like the chords section keys being all stuck(the keybed has 2 or 3 contact boards). Find some one that does know what they are doing for electronics especially keyboard, and then have them look around the casio chord keys section for corrosion build up or around the accompaniment ic chip.Seeing that all the functions work except I did not HEAR automatic chords, only automatic BASS, the chords section is faulty. Also, you should be able to shut off the stuck notes by switching OFF the MEMORY switch in the Casio Chord section. That switch makes the CHORD notes sustain. The only thing that you did not do was check the MELODY PIANO sound by itself.. Check that to see if the issue may be in the melody section for THAT sound?

[jorud]

7 hours ago, pianokeyjoe said:

That sounds like the chords section keys being all stuck(the keybed has 2 or 3 contact boards). Find some one that does know what they are doing for electronics especially keyboard, and then have them look around the casio chord keys section for corrosion build up or around the accompaniment ic chip.Seeing that all the functions work except I did not HEAR automatic chords, only automatic BASS, the chords section is faulty. Also, you should be able to shut off the stuck notes by switching OFF the MEMORY switch in the Casio Chord section. That switch makes the CHORD notes sustain. The only thing that you did not do was check the MELODY PIANO sound by itself.. Check that to see if the issue may be in the melody section for THAT sound?

 

thanks for the insight! i'll try taking off the keybed next and checking for any corrosion.. the memory switch is actually off in the video! i think the angle makes it look like it isn't but that doesn't solve the problem. hoping it's not a problem with one of the chips, if it is then i'm probably just gonna live with it haha

[Chas]

@jorud- Congratulations on acquiring a Casiotone CT403, though sorry to hear that yours is not functioning correctly. I have a 403 in my collection and it's one of my favourites of the classic Casios. It has some lovely warm tones, and the analogue drum/ accompaniment section sounds wonderfully vintage, almost like a Roland TR77. Mine is working fine, and the only issue it has ever had was when one of its Rifa  film capacitors blew up in quite a spectacular manner - so much smoke from such a tiny component! I replaced it with a better quality modern equivalent and it has performed fine ever since.

With regards to your 403, it clearly has an issue with the accompaniment section. Do the drums work/ sound at all? What about the bass accompaniment? From what I can hear in your video,  the Casio Chord feature seems to be stuck/ frozen and completely drowning out the drums and bass. Do any of the chord accompaniment switches make any difference at all? These old  "Casiochord" models tend to route all the accompaniment sections - drums, bass and chord - to a single volume control (the Accom/ Melody balance control in the 403) so it's not always easy to tell which section has the issue. Then again, IIRC they're all generated from  the same LSI/ CPU, so it's possible that the accompaniment LSI has failed or a component for clocking/ syncing/ triggering it is faulty. 

I suggest carefully examining the circuit traces for continuity, look for obvious breaks/ failings/ damaged components and also test the switches for continuity also as sometimes a jammed switch can cause an LSI to misbehave. It really is going to be a question of isolating components and circuits to try and find the route cause of the fault.

Apparently the CT403 is related to the MT60 model, so see if you can find a service manual for either of those that will help guide you. I've searched online but couldn't find one though. I have the CT403 Operation Manual in my archives, but not the Service Manual. They're always worth having and if I do manage to find one, I'll upload it here.

 

Anyway, I hope you get your 403 working properly, as asides from being a nice sounding vintage Casiotone, yours looks to be in very nice physical condition and with all its switch caps (they have a habit of falling off and getting lost). Good luck and let us know how you get on.

[pianokeyjoe]

Hi @Chas! The drums in the video above made a sound, the rock rhythm just sped up as he demonstrated. AND the base line also could be heard with the drum line, same Rock beat. The chord is the culprit.. The casio chord on most classic Casio keyboards was 3 voice polyphonic and it sounds like 3 notes are stuck down(usually the pins that output/input the chord notes)are shorted by something. While the film caps or a bad set of diodes(on the contact board itself where the chords are),could be shorted causing the held 3 notes that max out the polyphony of the chord section, I can also say it may be even simpler! flip the keybed over, remove the screws from the contact boards and clean all the liquid that may have spilled under the keys or remove some metal debris or ...errr...um.. penny or paper clip or staples that may have been stuck between the keys in that section.. As a Casio collector and keyboard player I have seen it all lol. I buy my Casios mostly in the fleamarkets in Northern Florida, Jacksonville FL and sometimes down south in Orlando and Tampa and can attest to these issues. His and yours are AC plug in units so no battery acid corrosion issues to blame, so maybe it is more complicated but from hearing and seeing this video again just now, it may be simpler more common annoying issue to solve..cleanliness is next to godliness?

[jorud]

@Chas@pianokeyjoe

 

thanks y'all! i ended up breaking off one of the buttons for rhythm preset while opening it up to clean it so i can see how they'd get lost easily 😕

 

speaking of opening it up to clean it, i've done it about 15 times and there's some improvements, the chord section mostly works now but it seems there's still one or two notes that are stuck.. surprisingly the circuit board looks pretty clean so i have no idea what to do at this point other than just not using the accompaniment section since i've been driving myself crazy cleaning it over and over again to diminishing improvements...

[Chas]

I'm trying to play catch up - been somewhat pre-occupied over the past few weeks.

 

@pianokeyjoe- ah, you are correct. The drums and bass accompaniment are there - I was originally listening to the video on my phone and couldn't hear the drums and bass under the chord drone on my phone's tiny speaker. Now that I've listened to it on my proper workstation speakers, I can hear them. I agree, definitely a chord section issue, though it's good news that the drum and bass accompaniment sections both work, if somewhat drowned out by the chords. I also agree that it sounds as if something may be causing a short on the circuit board/ component pins, either something physical has fallen inside and is touching them, or possibly a corrosion issue.

Also, I didn't know you were (relatively) close by to me, at least I am assuming that you are if you are purchasing your gear as far south as Tampa and Orlando. I'm in Bradenton, West Central FL, so literally a stones throw from Tampa and approx. 100 miles or so from Orlando. And I wish I could find flea markets that had old Casios/ Casiotones for sale! I keep checking the local thrifts and Goodwills in my area, and have never yet managed to find a single Casio keyboard in one. Most keyboards I find are the cheap no name/ strange name somewhat rubbish toy keyboards that I still pick up anyway for just a few dollars.

@jorud- Good to hear that you've made some progress! Yes, some of the button and switch covers on old Casios can be a little fragile. The three cream coloured switch tips at the left are normally the ones that get lost. My 403 had one missing when I bought it and it really bugged me. I then saw a slightly rough 403 come up for sale for pennies on a recycling site, and it only had one of the three switch tips. So I bought it, took off the switch tip and gave my 403 a complete set, found some generic black switch tips that fitted and looked OK on the rough 403, and bunged it on eBay at a low start bid. Low and behold, it ended up selling for many times what I paid for it! End of the day, the buyer was happy and my 403 had a full complement of switch tips  🙂

When you say that you are opening your 403 to "clean it" and it's made some improvements, what exactly are you cleaning? The fact that you've made some improvements and got the chord section mostly working suggests that you are definitely on the right track. You've probably done so already, though check the components and circuit board traces near the two LSI's. Especially as according to the the Table Hooters site:

"The quite complex analogue hardware of this instrument resembles the Casio CT-410V (besides that it has no synthesizer filter) and was apparently a predecessor of it. Like the latter it is divided in an accompaniment CPU and a separate main voice soundchip, although in the MT-60 not only the accompaniment CPU but also the main voice soundchip both poll the keyboard matrix. 

 

http://weltenschule.de/TableHooters/Casio_MT-60.html

The above applies to the MT60 model, which apparently is closely related to the CT403 and appears to share nearly all the same features and tones (interestingly, the MT60 has an arpeggiator whereas the CT403 does not). It's interesting to note the part about both the accompaniment and main voice CPUs/ LSIs polling the keyboard matrix. This is how the 403's accompaniment would know what to play depending on what keys are pressed down. If the keyboard plays all keys fine in tone mode only, then that indicates that the problem is likely between the keyboard matrix scanning section and the accompaniment LSI/ CPU. Therefore identify the accompaniment LSI (D910G if it's the same as the MT60) and check the traces, solder joints and any nearby components that might be a potential problem. Something might be visually obvious if you look closely, though it might possibly be a failed component also. 

Either way, I hope you do manage to get your 403 back to full health. They're lovely keyboards and as I mentioned above, they are one of my favourites of the vintage Casio models. Oh, and they look absolutely gorgeous and retro as well as sounding great! 

 

Edited October 19, 2021 by Chas

[pianokeyjoe]

@Chas Yes! I knew it was something shorting the chords line but again, sounds like just a few keys. Now I live up North and sadly, no fleamarkets here. My mom lives in North FLA where there are a surplus of places to buy goodies. Now I did go to a big fleamarket in Tampa or ST Pete when my lovely wife was gloriously alive and blessing my life! I found Casio, and Bontempi italian keyboards there as well as in Pawn shops in Tampa I found some nice synths, and drum machines for dirt cheap. I went to Bradenton for Christian youth retreat when I was a teen back in 1992. I brought and played on stage, my Casio HT700 at that time lol. The 403.. I wonder if he sets it to FINGERED mode, what happens?? In Full chord mode, you have the limited polyphony per "line" on the accomp side right? But in Fingered mode you have the benefit of 3 note chord play or single note play. I want to hear to see if a set of keys may be DEAD or stuck..

[CYBERYOGI =CO=Windler]

I had added some info here.

[aroot]

Hey there, any news on whether you were able to fix your keyboard? I have an MT-100 with a very similar issue and would greatly appreciate any ideas on how to fix it. 

[Grizzly]

Hi everyone! yesterday i buy one casiotone 403 and has the same issue, any ideas how to fix?