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YM26600/26700 IC Alternatives

 

Has anyone ever looked into modern alternatives for these fragile and rare 40-year old chips? I am wondering if it'd be possible to program an Arduino to handle key coding/assigning and D/A conversion on the KAS and KBC boards.

Cheers,

Jonathan
 

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Jonathan,

Duplicating the logic is easy. ?The big pain is the voltage. ?The Yamaha uses 4000-series CMOS and runs all the digital logic at +8.5 / -6.5 -> 15 volt supply. ?It’s offset above/below zero to interface with the analog circuits that run off +/- 15 volt. ?No modern chips run at this high voltage. ?Even 5-volt is history and 3.3-volt is only kept around for interfacing with older parts. ?All the chip guts these days are running around 1-volt. ? So, you end up needing tons of level-shifting chips to connect the Ardiuno (or FPGA) to the rest of the logic. ?Most circuits I’ve seen use chips that were intended for converting RS-232 (also fairly extinct) like the MAX232. ?The chips that were most commonly used won’t work anymore since they convert to +5v TTL.

?David


On Jan 16, 2018, at 9:39 AM, jonathan4051@... [yamahacs80] <yamahacs80@...> wrote:



Has anyone ever looked into modern alternatives for these fragile and rare 40-year old chips? I am wondering if it'd be possible to program an Arduino to handle key coding/assigning and D/A conversion on the KAS and KBC boards.

Cheers,

Jonathan
 

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Beside what David said - yes, someone did it already: Ok, it is not for the polyphonic series, but it shows, that is doable, and also that it would provide other advantages, like adding MIDI.


On 16.01.18 18:39 , jonathan4051@... [yamahacs80] wrote:

?

Has anyone ever looked into modern alternatives for these fragile and rare 40-year old chips? I am wondering if it'd be possible to program an Arduino to handle key coding/assigning and D/A conversion on the KAS and KBC boards.

Cheers,

Jonathan
 

Thanks, gentlemen, you've given me some hope, as I fear I may have fried my 26600 either by static discharge or by touching the +15V card riser rail against the keyboard PCB's (now I know to pull the keyboard toward the front before lowering the riser! Ugh..) . Even if I can find an original replacement (there's currently a 26700 on Ebay for $850!), or a donor CS-60, in the end it'll still be a fragile 40-year-old chip I'm throwing in there.
Old Crow's actually the tech that serviced this particular CS-80 back in '13. All new 4000-series IC's throughout.
 

So aside from Vss, Vdd, clock i/o's, etc, I count 33 connections to the 26600 operating at +8.5/-6.5V. Tons of level-shifting chips needed, indeed..
 

With the power off, I am getting a 70 ohm resistance between +15V card rail and ground - does anyone know if this is this normal?

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