Casio CZ/ VZ/ FZ - Pro Series

In the past I had this problem with some instruments. If I remember well, it was caused by some ground loop somewhere. I don’t remember how I solved it, it’s so many years ago… Probably by desoldering ground wire in some connectors on audio cables, just on one side… Probably it didn’t repair the real reason, but it stopped the zipper noise in audio signal.

Maybe it is confirmed by your finding that unplugging MIDI cables didn’t improve it. It has nothing to do with MIDI signal - this is too high frequency to be heard, and it goes different way than audio signal. The problem is inside the instrument.

Try to modify few audio cables and tell us if it helped.

And generally - check all connections in your studio if there’s ground loop somewhere.

Daniel Forro


> On Dec 21, 2018, at 1:13, xdumortier@... <mailto:xdumortier@hotmail.com> [CZsynth] <CZsynth@yahoogroups.com <mailto:CZsynth@yahoogroups.com>> wrote:
> 
> 
> 
> I did some more research while I was fixing some of the keys.
> 
> The midi noise/zipper sound is as loud as the synth sound when chorus is at maximum. When I lower the volume, the noise/zipper sound gets quieter (but of course the synth sound also gets quieter).
> The midi noise/zipper sound is very quiet when the chorus is at minimum, at ANY volume. But it's still there.
> 
> Pulling out connectors:
> When I pull the left connector "C E" from the motherboard, then the synth sound is gone, but I still hear the noise/zipper sound at full volume when pressing keys ore moving the wheels. Even with the chorus slider at minimum. The noise goes down in volume when I lower the volume slider.
> The noise is still there when I disconnect both connectors "C E" and "C K". Also when I disconnect the led's and the buttons from the motherboard.
> When I pull connector "C I" from the motherboard, I get no midi noise/zipper sound, but the screen shows a MIDI error, so I guess there is no midi noise because MIDI is not active.
> 
> Changing settings:
> The tone of the noise/zipper sound changes slightly when I change the KBCH (keyboard midi channel).
> The noise disappears when I use the MIDI ON/OFF button to turn off midi (but I need the midi to sequence).
> 
> Connected cables:
> I can hear it through the headphones jack and through the L / R jacks.
> The noise/zipper sound can be heard both when MIDI jacks are unplugged and when MIDI is plugged while sending MIDI data from the computer to the CZ-1.
> 
> It's pretty clear MIDI has something to do with this noise. Midi is sent and received correctly, but it seems like the midi data is going through the sound path.
> 
> I see no bulging capacitors and everything looks clean inside. There is no corrosion or battery leakage.
> What component could be causing this?