Casio SA keyboards
Casio SA Keyboard Modification.
This is an engineered modification which works on most of the Casio SA series ( SA-1, SA-5, SA-7, SA-8 etc). There will be an Amplifier chip ( No AN8053 ) common across the SA series and a mask programmed CPU which will be made by OKI and have the part No M6387-xx where xx is the variant for the specific keyboard it is installed in, in the case of the SA-5 it is M6387-16. The different variant number accommodates different key / button layouts of the keyboard it is fitted into, the PCM sounds however remain the same. There are 5 interesting modifications that can be easily fitted:
1) Pitch Shifting
2) Power Crash
3) 5th’s Switch
4) Glitch Randomizer
5) Filter/ Feedback Adjustment
1) Pitch shifting. The CPU runs at a fixed speed of 22Mhz which it needs to create the internal sounds out of its Rom and to run the main program that scans the keyboard / buttons and plays the sounds. It has to run at a precise fixed speed as a lot of the internal processes are calculated by dividing the clock signal internally. It is not possible to just remove the Casio’s crystal and swap it with another, as the original crystal has 3 legs, and most others have 2. In order for the crystal to oscillate it needs two capacitors, these are built into the original crystal and come out on the 3rd pin in the middle. To successfully swap the crystal we need to add two 22pf ( very tiny ) capacitors to a new crystal and complete the oscillator circuit. I have got it to run as low as 6Mhz but at this speed it executes it’s system program slower also, so there is a tiny delay after switch on before the keyboard responds.. this is normal! It is also possible (although I have not tried) to increase the clock speed and put a 30Mhz crystal in, which would increase the pitch of the keyboard.. it may even go higher, just like overclocking your PC!
2) Power Crash. The CPU needs a stable regulated voltage to run normally. If a variable resistor is put in series with the supply to the keyboard (removing the DC in Jack off the PCB and using the solder pads works very well) it will reduce the available voltage the CPU can use, and there is a threshold where the CPU does not have enough power to run correctly, but it has enough to not stop, this causes random sounds.. glitches in playback etc. Different results are achieved if the speaker is removed or not as the speaker requires a lot of power to run, the CPU does not glitch out as much with it in circuit, it just gets quieter when the power is reduced. A good value potentiometer is 500 ohm, which maybe hard to get but can be made with a 1K pot with a 1K resistor in parallel, giving a 500 ohm potentiometer
3) 5th’s Switch. When you play a key, activating this mod will play a second note at the same time, either a 5th up or down depending on the position of the toggle (centre off toggle switch needed). This mod simply fools the CPU into thinking an extra key is pressed. All the keys are wired in a sort of X Y matrix that the CPU scans the X and the Y lines to see if a key or button is pressed. By shorting out an extra line, when the key is pressed the CPU sees 2 key presses and plays 2 notes. The switch is wired to short out either 1 line up or 1 line down of the line that scans the keyboard. It may not work on all the SA series as the CPU is configured to scan different button arrangements on different models, these pins may connect to buttons rather than keys on a different model.
4) Glitch randomiser. This causes a random effect on the CPU dependant on how the knob is set, and what the keyboard is doing at the time. I previously mentioned that the CPU constantly scans all the keys and buttons.. This mod takes the final amplified audio signal out of pin 5 of the amplifier chip and injects it back into the scanning matrix via a 1Meg pot. Instead of the CPU seeing a definite signal (such as when a key is pressed) it doesn’t know what to do when it finds a much amplified audio signal where it is expecting a scan signal, and it locks the CPU up. If the keyboard is idle and not making any sound, then turning the knob has no effect as there is no audio signal there to inject back into the CPU.
5) Filter / Feedback pot. This works exactly the same way as sticking a live microphone in front of an amplifier speaker and you get howl or the Larssen effect ( usually heard at drunken speeches - or after dinner events ). The modification takes the audio output frm the amplifier which is quite large, and injects it back to the CPU output that is connected to the input of the amplifier chip, which then amplifies it further, feeds it back and amplifies it more.. the amplifier chip cannot cope and goes into self oscillation which is heard when the knob is wound right up. The Potentiometer used is a 1K pot, but a trimmer is also fitted in the 1 leg, so with the pot turned right down there is still some resistance between the input and output of the amplifier, otherwise it would feedback all the time. When setting up, adjust the trimmer so that oscillation starts approximately 1/3 of turning the main 1K potentiometer. When the amplifier is in self oscillation / howling, it draws a relatively large amount of power, which causes the power glitch mod to not work properly, it is better to put a switch between the 1K potentiometer and the wire to pin 5 of the amplifier chip, so the feedback loop can be broken
There are further potential modifications, such as Rheed’s body contacts and instability pot.. these both work on the Crystal oscillator circuit, and cause the CPU to miss a clock pulse causing a crash in the internal program. The same effect can be achieved by switching the clock speed, as the time it takes for the switch to disconnect one crystal and connect the other by moving the lever, may only be a fraction of a second for us, the CPU has missed literally thousands of clock pulses and doesn’t know where it is in it’s program. Very occasionally I have managed to play a note, flip the switch and it continues to play but dropped in pitch 99% of the time it will crash the CPU.. the most spectacular results occur if you have the power reduction pot right on the threshold, where the SA is fighting to make sense of what is going on, and then you change the crystal.. utter mayhem 
P.Parry Aka OCEANUS 15/1/08
PlasticAnimal said:
January 26th, 2010 at 12:17am #
Hi, I’ve found a similar bend as the filter/feedback on the sk-1. It sounds great and gives chord mode some insane bass. The only problem (besides loss of polyphony in normal play) is that after a while you get a lot of lo-fi distortion and some drop in volume. It seems like it clears up if I leave it off for awhile. I’d love to fix this though. Any ideas?
casper said:
February 18th, 2010 at 1:05am #
@PlasticAnimal: It’s pretty hard to say what is going on there. Generally any effect that changes noticeably over time is to be avoided. Safe effects will be the same no matter what. Some effects will change as the battery dies, but other than that be careful of changing effects.
Something I like to do is use a current meter on the power supply. Then when I hook up potentially dangerous bends like the one you’re talking about I can see if it pulls lots of power. If it does, then it’s no good.
EstolidaMelopea said:
March 19th, 2010 at 10:14am #
hi casper! king of kings (of the bent)
a simple question..
to make the crash power hack, i need remove the AC input jack?
how conect the power on the keyboard?
other question (i have time)
i have a sa-40 (magic dial).. can you see this picture (http://weltenschule.de/TableHooters/picts/Casio_SA-40_open.jpeg)
and say me:
-the sa-x hacks can be in your keyboard-?
(i have a very pro hack to this toy, and the info is in my blog.. buy need more, mooooree!)
thnx u very much!
and sorry for my english..
PHOBoS said:
March 19th, 2010 at 4:19pm #
Thanx for sharing this information! I recently did a SA-8 bent, but with this information I can add some more modifications. =)
I just got myself a second one today, so I’ll probably leave the first one as it is and start working on the that one. (Have you ever tried bending 2 keyboards by making connection between them ?)
AWAKE said:
March 30th, 2010 at 10:12am #
Hmmm… I have done the crystal swap, but with no luck. I had a few 6Mhz crystals and ordered 22pf caps, built the circuit, checked it thrice, and nothing. It just won’t come on when the switch to the 6Mhz crystal is flipped. It turns it off and the unit won’t power up when the alternate crystal is selected.
I have made it go into a crazy oscillation followed by a spectacular crash…once. Any ideas?
The 5ths switch is brilliant!
Keep up the fine work sir.
casper said:
April 11th, 2010 at 12:40pm #
@EstolidaMelopea:
You don’t actually HAVE to remove the power jack to install the crash knob. I think the better way to do it is to cut the lead coming from the jack then installing the adjustment on both sides of the cut. The crash will work best when the keyboard is battery powered. It probably won’t work when you use a power adapter.
I’ve never worked on the SA-40 but the SA-X bends will probably work.
casper said:
April 11th, 2010 at 12:43pm #
@PHOBoS: Yes I’ve done some cross bending between 2 keyboards. It’s worth trying. Sometimes it awesome and sometimes it’s not. IT works best if you connect the ground of both keyboards or if they share the same power supply.
casper said:
April 11th, 2010 at 12:46pm #
@AWAKE:I’ve heard from a few folks lately who are having similar problems. I’ve actually never tried the crystal swap. Most of the bends in the diagram were supplied by a bender named OCEANUS. I’ll try it out and see what happens.
yto said:
May 31st, 2010 at 10:46pm #
thanks!
PHOBoS said:
June 21st, 2010 at 2:33pm #
After doing some other things I returned to my SA-8, and have some info I’d like to share. I draw a comnplete schematic of the circuit to get a better understanding which clearly showed some unused connections in the button matrix. Adding these buttons gives you 75! extra sounds (so all the sounds from the SA-1), 3 more demo’s and a cowbell. There are still a couple of connections which don’t seem to do anything.
To get all the SA-1 sounds do the following:
1) rename the original Tone buttons so the numbers correspond with the ones on the SA-1.
Tone1 -> Tone0
Tone2 -> Tone1
Tone3 -> Tone2
Tone4 -> Tone3
Tone5 -> Tone6
2) add buttons between the following pins of the OKI chip:
26-15 -> Tone4
25-11 -> Tone5
25-13 -> Tone7
25-14 -> Tone8
25-15 -> Tone9
For the 3 extra demo’s add buttons between the following OKI chip pins: 24-15, 24-16, 24-17.
And if you need more cowbell add a button between pins 23-12 of the OKI chip.
stusvend said:
July 13th, 2010 at 8:51am #
Just FYI for everyone, they have several different 500 OHM pots to choose from at allelectronics.com Taydaelectronics has some for .40 cents a piece. You can get lower quantities for cheap prices from these places too. No, I dont work there
HTH
nomad said:
July 23rd, 2010 at 6:01pm #
hey all, I’m wondering if you can help me add a volume pot to an sa keyboard.
thanks
Ben SImon said:
July 25th, 2010 at 10:13am #
hey all, I wondering how to add a volume pot to a sa keyboard.
thanks
casper said:
August 7th, 2010 at 9:27pm #
@Ben and Nomad:
Check out my output jack/volume control schematic for some details:
http://casperelectronics.com/finished-pieces/circuit-bending-tutorial/audio-jacks-and-volume-control/
samspike said:
August 19th, 2010 at 7:28am #
PHOBoS tips all worked great for me, except one of my additional demos is coming out the same as a pre-existing demo. It’s possible that it’s my wiring that is at fault however.
I would however propose a variation:
PHOBoS’s number of the extra sound buttons, keeps the patch numbers the same as the SA-1, but it means the existing buttons on the SA-8 front panel are kind of in a funny order (0,1,2,3,6 with 4,5,7,8,9 somewhere else).
Instead my suggestion (Yes I’ve tried this) is to keep the existing tone buttons labelled 1 to 5, and label the new buttons 6 to 0, then re-order the SA-1 patch list to match this.
In other words:
Tone 1 button stays as tone 1
Tone 2 button stays as tone 2
Tone 3 button stays as tone 3
Tone 4 button stays as tone 4
Tone 5 button stays as tone 5
New buttons:
Tone 6 is a push-to-make button connecting pins 26 and 15 on the OKI
Tone 7 is a push-to-make button connecting pins 25 and 11 on the OKI
Tone 8 is a push-to-make button connecting pins 25 and 13 on the OKI
Tone 9 is a push-to-make button connecting pins 25 and 14 on the OKI
Tone 0 is a push-to-make button connecting pins 25 and 15 on the OKI
Now the two digit tone numbers 11,12,13,14,15… upto 55 are unchanged from the descriptions on the original front panel, but the new buttons allow access to the additional sounds.
The patch list arranged to match this button numbering scheme is:
samspike said:
August 19th, 2010 at 7:28am #
00 STRINGS/OBOE
01 TRIANGLE
02 CONGA/AGOGO
03 COWBELL/CLAVE
04 TOM
05 BASS/PIANO
06 ROCK DRUM
07 SWING DRUM
08 BASS/TRUMPET
09 PIANO/FLUTE
10 ACCORDION
11 PIANO
12 ELEC PIANO
13 HONKY-TONK PIANO
14 HARPSICHORD
15 PIPE ORGAN
16 JAZZ ORGAN
17 ELEC ORGAN
18 CHURCH ORGAN
19 STREET ORGAN
20 CLARINET
21 BRASS ENS
22 WARM BRASS
23 TRUMPET
24 TUBA
25 ENGLISH HORN
26 BRASS HIT
27 WIND ENS
28 OBOE
29 BASSOON
30 BRASS-STRINGS
31 SAMBA WHISTLE
32 WHISTLE
33 QUENA
34 FLUTE
35 BAGPIPE
36 FLUTE-VIB
37 OCARINA
38 HARMONICA
39 CHORUS
40 SLAP BASS
41 STRINGS
42 WARM STRINGS
43 VIOLIN
44 VIOLIN-PIANO
45 JAZZ GUITAR
46 CELLO
47 ELEC GUITAR
48 MUTE GUITAR
49 METAL GUITAR
50 PEARL DROP
51 GLASS HARMONICA
52 FANTASY
53 WAW VOICE
54 TWINKLE ECHO
55 COSMIC DANCE
56 METAL LEAD
57 CATHEDRAL
58 PLUNK EXTEND
59 POP LEAD
60 SHAMISEN
61 ELEC BASS
62 WOOD BASS
63 SNARE BASS
64 UKULELE
65 MANDOLIN
66 BANJO
67 SITAR
68 HARP
69 TAISHOKOTO
70 SYNTH-BASS
71 SYNTH-PIANO
72 SYNTH-CELESTA
73 SYNTH-CLAVI
74 SYNTH-ACCORDION
75 SYNTH-LEAD
76 SYNTH-BRASS
77 SYNTH-REED
78 SYNTH-STRINGS
79 SYNTH-GUITAR
80 TYPEWRITER
81 AIRPLANE
82 AMBULANCE
83 INSECT
84 EMERGENCY ALARM
85 TELEPHONE
86 LASER BEAM
87 COSMIC SOUND
88 CAR HORN
89 COMPUTER SOUND
90 WADAIKO
91 VIBRAPHONE
92 MARIMBA
93 CHURCH BELLS
94 BELLS
95 ETHNIC PERCUSSION
96 GAMELAN
97 AFRO PERCUSSION
98 SAMPLE PERCUSSION
99 MATSURI