[sdiy] CZ-1000 update and memory mod help

John P Shea info at extrinia.com
Wed Mar 11 23:59:54 CET 2020


Hi MTG,

Don't get too freaked out! Without even looking at the schematic, you'll
know that it's an 80's era (probably 8-bit) era microprocessor, perhaps
even an early microcontroller. To support the CPU, it will typically need a
clock circuit, and no doubt there will be power on reset handling.

The micro will need to execute a program, and this will probably be in an
external ROM. Similarly, you need to store those presets, so some (battery
back up) RAM in there too. Now, the CPU will have to process inputs. What
inputs are on this synth?

Firstly, it will need to do keyboard scanning. The CZ-1000 is 4 (x2 osc) or
8 note (x1 osc) polyphonic, so the scanner will be some sort of rows and
cols jobby.

Moving on, it will also need to handle the buttons. Another scanner
possible.

Any other inputs? Yes, MIDI DIN, do there will be the opto and serial
circuitry for this.

Now for outputs. Obviously, we have the phase distortion audio out,
probably handled via an outboard DAC and filter/buffer. Next, we have
digital outs, including the button LEDs, the LCD, and MIDI Out, which could
be just a 5V non-inverting buffer.

To handle all of those peripherals, the CPU sends (probably) 8 data lines
to each. And to uniquely address each one, there will be address decoding
circuitry, look for the "CS" or chip select on each of the peripheral chips.

The point is, this is a known pattern. Because there will be a lot of
Japanese specific chips in there, it may may finding individual data sheets
a bit tricky. But its just a micro with some peripherals at the end of the
day!

All the fun part is in the ROM :)

Regards,
JPS

On Thu, 12 Mar 2020 at 02:00, MTG <grant at musictechnologiesgroup.com> wrote:

> Wow, that (original) circuit is insane. Hopefully someone on this list
> can understand all of it because I sure can't.
>
> On 3/9/2020 9:31 PM, Joe Frey wrote:
> > Hello all, To those that answered my original post asking for guidance I
> > found the problem. The output relay had gone bad and needed to be
> replaced.
> >
> > So, after getting the synth to sound good again I decided to make an
> > improvement and add ram power management so my custom patches wouldn't
> > disappear when I put the synth in it's case for half a year. It turns
> > out there's a chap that made a mod that I found out about that people
> > say works. I contacted him and though he no longer provides the kit he
> > did supply the info to make that mod.
> >
> > https://www.artefacts.nl/bitsandpieces.html
> >
> > He also gave this advice, "_Before you start modifying the CZ you should
> > check if you can change the standby voltage as described in the
> > installation manual_. You should also check the RAM chips get a voltage
> > between 4.8Volt and 5.2Volt when the unit is switched on. If you can not
> > get these voltages within range the kit will not work."
> >
> > Of course being me, I ignored the first line of the instruction and made
> > and installed the mod. DOH! Now, everything is cozy and in place but I
> > can't use the trimmer to get the standby voltage down to 3.2V. I can get
> > it to 3.7V. I am wondering if I put a diode in the end of the VBR
> > regulator circuit to use the diode drop and try and  get from 3.7 to
> 3.2V?
> >
> > The schematic is found here.
> >
> >
> https://www.synthxl.com/wp-content/uploads/2018/01/Casio-CZ1000-schematics.pdf
> >
> >
> > And the VBR power supply is at page 4, grid 4F. And, the ribbon cable
> > pin I am measuring voltage at is pin 9.
> >
> > Any advice is appreciated. JoeF.
> >
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