[sdiy] CZ-1000 update and memory mod help

[MTG]

I found the reset and battery voltage sufficiently insane. It needs to 
be completely rethought. I don't know how they got where they did, but a 
friend of mine made a MIDI processor out of TTL gates, so I guess 
anything's possible.


On 3/11/2020 3:59 PM, John P Shea wrote:
> 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 
> <mailto: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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