Hello there,
I own a Kawai SX-240 for a long time.

When I have the time to turn it on, I discover new sound directions for this Synth, that have to do with its tone and sound possibilities. Ok, it is a great Analog Synth with patch layering, cleaver routing techniques, with a nice warm 80ies sound, but I am wondering if someone could write a new ROM code to make the Synth CC controllable from an external source, and/or add a higher resolution to parameters.

I believe that this Synth could beat the most of the 2 OSC Analog Synths out there, if its parameters could be controlled via knobs. The latest Glilgi upgrade for the Prophet 600, for instance, offers higher resolution parameters (0-255) and added functions such as an external LFO, velocity etc... sad not to have such an upgrade for Kawai SX-240 too..

Please let me know your thoughts about it

yep i would also love this, even just being able to select a midi channel would be a great help (mine is the version where holding a patch number on start up has no effect).

I know that this work may take a long time and research but I believe that the instrument deserves it.
Kawai SX-240 can do sounds that are not possible with any other Analog Synth. It has its own character.

It's sad to have such a simple operating system.
It is an instrument with a good hardware (for 1984).

We may vote for an upgrade here, in this thread, if you agree.

Not to be a downer, but I hear they are pretty difficult to work on.

the reason i sold mine. it was a great sounding synth, but it was a disaster to maintain.

For it to be a worthwhile endeavor it really needs to have been a popular, reliable, and good sounding board....not to mention not riddled with road blocks that would prevent computer mods challenging, expensive, or impossible. And a labor of love, for your particular coder who will also have the particular synth in their possession, and be willing to gamble their time that they'll actually be able to get paid for it. It's a pretty narrow market to see how many owners care about the end result, are willing to pay for the components (and tech time to install), and have a good working example to begin with.

I don't speak for Kawai owners...but I have owned a few more popular synths that have aftermarket upgrades...and I personally don't believe they are worth the cumulative investment. Rather than spend the money to "hot rod" and make a really confusing non-factory interface with a couple nice features, I'd rather live with the limitations as I have for years, or buy something brand new. But that's just my opinion.

Why was it a disaster to maintain? I worked on one earlier this year and I didn't notice anything particular to worry about, other than pcb track breaks around the switch LED's

I bought one a few months ago and it wasn't difficult to coax it back to life. In addition to new firmware, I'd love to see replacement graphics as my front panel is peeling.

Kawai SX-240 is manufactured using expensive components and a wise architecture, therefore in most cases, the issues have to do with battery corrosion or in worst case with the death of a 4051 IC which is already the most failing part in history of Analog Equipment.

Anyway, as every parameter of SX-240 is controlled by CPU and the Synth has built in MIDI In/Out ports, if someone could re-program its ROM to support CC parameters to be able to control the synth via an external controller (like BCR2000 or Kenton Spindoctor/Freak etc), this could raise the potential of the instrument (not his tone/character), with only a simple ROM replacement.

Then, at a later stage, we could decide for additional updates, for instance if parameters could have a range of 0-255, instead of 0-99 or give the instrument velocity playing via an external keyboard, just like it has already happened with Prophet 600 and GliGli upgrade or Jupiter 6 Europa and many other Synths out there...

Of course this Project needs a good Programmer and the sources of the current ROM code.
If we ask the sources from Kawai, it will not be a problem to give them to us (I believe).

And of course we have to pay for this, covering the costs of this Project.

The Battery damage is something we Techs deal with on a regular basis, and dead 4051's are not just a Kawai thing, they die in every Polysynth as they all have them. Getting the source code from Kawai... well I wouldn't hold out too much hope.

Kawai has no replacement parts. zero. good luck sourcing the firmware.

not any answer from Kawai yet, any other ideas about finding the source code ?

A good place to start is to check the schematics and see if the design uses a standard microprocessor or microcontroller. Many synths of that era used off the shelf processors like Zilog Z80 or Intel 8048. One you know that the next step would be a dump of the EPROM(s) and disassembly of the code. After that would be a breakdown of what each portion of the code is actually doing and how the digital portions of the synth talk to the analog parts.

Not to trivialise this process, because its a lot more complex and tedious than what I'm outlining here. What you may find is that the processor is maxxed out already and you might have rig a microcontroller that supports a faster processor but still talks to the digital parts of the synth. Laszlo had to do this with both the IO and Minerva upgrades for the Jupiter 4 and Juno 60.

I did some digging. The SX-240 uses two 8031's which are a cut down version of the 8048's successor, the 8051 -- it has no onboard ROM so needs to use an external ROM (in this case an EPROM). On the schematics one 8031 is used as a Master processor and the other is a Slave, each has their own associated EPROM with code. I assume the Master processor is handling time critical tasks like scanning the keyboard and the main panel for input while the Slave is generating things that aren't time dependant. There may be communication or handshaking between Master and Slave or they may run independantly, but it's likely the latter. Many synths have separate processors for just scanning the keyboard and dealing with the multiplexed signals from the panels -- in fact the Jupiter-4 and the Polysix both use 8048's for just such a purpose (and perhaps unironically the 8048 was also first used in IBM keyboards -- the typing kind -- to scan for input)

The Master EPROM is a 27128 (16Kbyte) and the Slave is 2764 (8k) EPROM. Should be duck soup to dump both of these in a modern EPROM programmer and run through an 8051 disassembler (8051's are/were quite popular and the 8031 should be functionally identical from a programming standpoint). Both 8031's are clocked to 12MHz using the same clock crystal -- 12Mhz is the maximum speed of the 8031, so no room for overclocking.

8031 reference:

http://www.idc-online.com/technical_...controller.pdf

SX-240 schematics. If you end up using these you should send a few bucks Bob "Sounddoctorin" Weigel's way as he generously spent many hours scanning these in.

http://sounddoctorin.com/synthtec/kawai/sx240.htm

(I've mentioned Bob twice on GS today -- GOLD STAR!)

Great info dude
We have learned a lot.

First of all we need to have the .bin file from each Eprom, using an Eprom Programmer.
I have the G540, I hope it is compatible with 27128 and 2764.

The ROM IC inside my Kawai SX-240 is not socketed to get the .bin file.
I will see what I can do.

I want to bump this thread just because I want it to exist. I would gladly pay $500 for a kiwitechnics cpu upgrade board for this synth, if it ended up being compatible with the patch editor. The layering aspect of this synth is what gives it an immense sound, and that doesn't even work correctly with the current midi implementation.

Kawai SX-240 Rulez !!
I attach the original ROM file of Kawai SX-240 as I promised.

Download it here:
http://s000.tinyupload.com/?file_id=...11915270256508

I have informed Robert (sounddoctorin') about this project. He is currently very busy. He also informed that this project could be very complex.

So, if we finally decide to proceed with the CC upgrade and Robert has the time to deal with it, we will have to pay him for his work. Then the upgraded ROM will not be published for free.

I have provided him the link of this thread.

Please let me know any thoughts, ideas etc.

Gligli, tauntek, kiwitechnics, vercoven and I think there are a few others have taken on stuff like this. I think the biggest problem is that there are so few sx240s out there.

Personally i would gladly spend $500 on a full kiwitechnics cpu board replacement with compatibility with the patch editor.

Forgot tubbutec. If anybody could do it, he has some great stuff too

The SX-240 is equipped with MIDI ports and filter/envelope parameters have already 100 steps. It has also both CPUs. That's ok !!

The goal here is not to built a board like Kiwi upgrade. SX-240 does not need it. It is well equipped from Kawai. In this project we have to add some additional Midi CC code (to the current ROM), in order to control the Synth via the knobs of an external controller, like BCR-2000.

By the way, I just found this demo and I can't believe it:

https://www.youtube.com/watch?v=OkCjC3-K4z4

Haha! Thanks, actually my demo. The SX is a great synth that really deserves a firmware upgrade. For the demo every sound was created individually in the 240. The piano isn't great, and the mix is pretty muddy, but it is all genuinely SX-240. Once you start shaping the sound in the synth it gets dark pretty quick. Still, when you layer it up you really get a sound that is very specific to all the traits of the SX-240 which is what I wanted to hear before I got the synth myself.

Glad you liked it

You have done an excellent work mate, really fantastic

Hey, sounds great plasmasynth, love the Brass patch. I'm new to the forum, just joined actually. I'm hoping to see some good news in the future as I follow the thread . The Sx-240 is certainly worthy of the efforts and would be glad to pay for an upgrade also , so count me in

Thanks for sharing this, its from the master eprom: kawai 4036d or from 8031.

I have several problems with my sx240.

I have replaced the battery with a new one but the midi input doesn´t work but transmit by the thru port.
I can only load 4 banks with the loading tape way because an error happens.
And I have a eternal release in all banks.

I have check the track near the battery acid zone but are ok.

Any idea?

Thanks

I encountered that the audio signal from laying the patch file on a notebook wasn't hot enough. I think I had to route it to a small amp to boost it. I was able to get it to load all the banks after that.

Sorry dude but you may have to open a new thread for this issue.

Not many users out there positive for the upgrade but there is always a hope.

Count me in too.

Reupload, maybe? Somewhere safer would be nice, too, so it don't get deleted after just 100 days. Zippyshare? Mediafire?