Casio SA-1 & PT20

[computer at sea]

If you have a SA-1 with both these mods then I urge you to build a LFO with a 555 and DIY Vactrol and then run the (+) side of SA-1's audio through the light dependant resistor side of the vactrol before connecting it to the speaker or jack

So one of the legs from the LDR would go to the + wire and the other would go to the speaker?

Fussing around with my SA-1, trying unsuccesfully to remember the specifics of the above technique, I found that if you put the LDR across the two terminals on the djsynchro noise pot you can get a pulse effect.  The flash of the LED triggers the distortion. 
Probably not worth building a new oscillator for, but if you have one just kicking around it opens up another option.

[jamiewoody]

That jumper wire just to the right of the word SPEAKER is the one i'm talking about. Cut that and wire a pot accorss the gap.

I can't remember where that image came from but its from some circuitbending site so if it belongs to someone who recognises it, let me know and i'll credit it to you.

i would like to try this. which value potentiometer should be wired here?

[jamiewoody]

i saw a photo of a 500k pot for POWERCRASH wired in a different place: the contact for the power supply jack.

which place is best?

[Circuitbenders]

Its exactly the same thing, if i recall correctly both the battery power and the jack power go through that jumper.

I know for a fact theres some discussion either on this thread or elsewhere on here about pot values, the search function is your friend.

[jamiewoody]

this is good stuff! ;-)

so, is that pretty standard on most casio boards? if i see a jumper to the right of the power jack?


also, what about polarity? does it matter which side goes to which on the jumper?

(i admit i am not as intuitive about electronics as the status quo on here...but i am here to learn...dumb questions are better than dumb mistakes. thanks for your patience.)

[Circuitbenders]

As far as i know you'll only see that jumper on an SA1 although i could be wrong and you might see it on other. If you're putting in a voltage drop crash pot i'd always wire it on the positive side of the supply. It doesn't matter which way round you wire a pot if its wired in line with the positive supply. The only difference it'd make is which way you have to turn the pot.

It shouldb't be that hard to trace the power rails on any cheap keyboard, just follow the circuit board traces from the power jack and/or the battery compartment until it gets to a component. Wiring in a pot before that point should probably give you a variable voltage input.

Getting hold of a multimeter might be helpful for tracking down the positive and negative rails if you have any difficulty.

[computer at sea]

i saw a photo of a 500k pot for POWERCRASH wired in a different place: the contact for the power supply jack.

A 500K pot will be about a zillion times too big.  Try a 500 ohm pot.

[badbarcode]

hi guys

I found an interesting "decay" control for my SA-1

it's possible create very cool sounds using this  in combination with a distortion pot

[Obi]

Hi guys

I am new to bending and the whole world of electronics in general and trying out a few SA-1s, following some of the great diagrams and tips here. Haven't had much luck yet, and just wanted to see if there were any general tips on how to diagnose problems. I appear to have killed one and the other two were bought 'untested and as seen'. I can get a few notes out of one before it, almost literally, coughs, chokes and dies. I can keep doing this by turning it off and on again, though it won't do it every time, but I can't get it to play more than a few notes. I haven't added any mods except add a line-out jack and battery pack. It doesn't look that great inside, and the battery coil is rusty.

Also, after the keys stop working, I can get various low hums and crackles by touching screwdrivers on the chip pins corresponding to glitch and other bends seen in the diagrams, so it's clearly still live and responsive in some way, but not providing any of the wonderful madness I got from the same glitch connections on the other one before it stopped working, so I don't know what the problem is with this one.

As I said, I'm trying to learn how everything works from scratch, so any suggestions for trouble shooting, much appreciated.

Cheers