Casio CZ/ VZ/ FZ - Pro Series

When the relay fails over time and they always do, the chorus slider and circuit become big noise makers and signal killers. I don’t know if that’s what is happening to you, just tossing that idea out there. There are also documented issues with MIDI noise on CZs.
  Paul T 
CZ-1
CZ-5000
CZ-3000
CZ-101
HT-6000
VZ10m 
FZ20m

From: xdumortier@... [CZsynth]
Sent: Thursday, December 20, 2018 8:15 AM
To: CZsynth@yahoogroups.com
Subject: [CZsynth] Re: midi noise problem



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?











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