This video looks at fixing a broken, cheap toy Casio keyboard.
via organfairy:
I got this little CASIO SA-10 from a jumble sale. It cost me a massive 10 dkr – the equivalent of 2$.Unfortunately there was no sound but it turned out to be just some old batteries that had leaked all over the place. This video shows the restoring process where I first take it apart. Then I wash the plastic parts and clean the contact pads. And finally I put it together again and test if it works.
The music that comes with this video is something I made myself and it is played on the Yamaha HE-8 organ,Viscount RBX-850 organ, Roland JX-8P synthesizer, Korg Rhytm 55 drum machine, and the melody is played on a Yamaha PSS-12 and a CASIO SA-1 toy keyboard. The SA-10 that is shown in this video has the same sound chip as the SA-1 but four note polyphony instead of two.
Actually CASIOs are quite easy on the batteries. The old partially analogue models had a heavy power consumption. But the digital models – like the SA series – can run for a surprisingly long time on a set of batteries.
I think CASIO used a special synthesizer that more or less went into standby mode when no keys were pressed. On some of the voices the release sounds as if an amplifier is turning off on the last part part of the envelope.
The smallest SA keyboards – like the SA-1, SA-2, and SA-3 – had two tone polyphony. The bigger models – like the SA-10 and SA-20 – had four tone polyphony. In general polyphony is not rare on toy models. Even many of the cheap Chinese "no-name" keyboards are polyphonic. The thing that costs today are ROM memory so the cheap models have short wavetable loops and only 4 or 8 bit resolution.