Hi, long time lurker and information utilizer.
Awesome techniques on here so I gotta say many thanks.
I think Ive finally fried the IC in my casio SA21 after sending a voltage through the wrong pin. It now no longer powers up. I'm just trying to find out if anyone has had success replacing this OKI chip ...or is not worth trying to track it down.
Its such a cool machine and I would love to resurect it but I fear its gone past the point of no return.
I suspect the only place you're going to get another one of those in less than industrial quantities is from another casio SA, or from someone on ebay by some freakish chance.
They claim to have two M6387-13 available at http://www.mark5.co.uk (http://www.mark5.co.uk) if you do a search, but i've never been entirely sure how that site actually works, or even if thats the same IC.
Have you checked on the +ve power pin of the chip to see if you are even getting any power too it? There might be an issue elsewhere causing power problems and the chip is fine.
Thanks for the suggestion CP, will check the positive power pin again as well the traces back from it.
I've also contacted a few IC suppliers in hong kong who claim to have the OKI chips in supply however I'm not sure if these are "pre-programmed" chips or if they are simply blank and need the ROM to be written in.
Thanks CP, managed to isolate the problem down to one capacitor, replaced it and then turned back on and.....
It works!!!
So it wasn't a fried chip and the SA lives to fight another day. Lesson being don't give up til you've tested every last component.
Now for that glitch mod.