[sdiy] Casio CZ-1000 will not power off.

rsdio at audiobanshee.com rsdio at audiobanshee.com
Sun Mar 15 08:04:30 CET 2020

On Mar 14, 2020, at 8:45 PM, frey at radioles.com wrote:
> Hello all, the saga continues. I replaced a relay for the audio signal and my synth sounds good and clear again. But, evidently I have damaged something. When I try and turn off the unit the audio shuts off but the display and controls stay on and activated. Once I unplug the unit’s power supply from the outlet the synth stops. When I plug it back in it is off until I press the on button and then the synth works normally. Then again, when I press the off button. The sound stops but the lights and display and controls remain active.
>  I understand that the power/amp board sends a power off signal to the cpu board through a ribbon cable. I have checked the pins on the cable for continuity and all points have passed. 
>  I am wondering if perhaps one of the components that send the cpu off signal have failed.
>  I am a little inexperienced at troubleshooting and am wondering if I should just start changing electrolytic caps in the circuit?
>  Anyone have any experience that can advise? Thanks. JoeF.

Hey Joe,

Never change electrolytic caps when you don’t know what’s wrong - new ones don’t fix mysterious errors.
Never change anything new when you don’t know what’s wrong - first find out how you made things worse.
Never change electrolytic caps.

Seems likely that you could have shorted something - maybe you left a blob of solder rolling around in there when you changed the “relay"

Your best bet is to look very, very carefully at the work you did, and see what you might have changed. You’ll also have to look around in areas where you didn’t do any work to look for small wires, pieces of metal, or maybe a screw that cut through a wire, or something you didn’t put back exactly like you found it. You might even need a magnifying lens to find something that’s barely visible.

One of the first rules of troubleshooting is that once you’re out on a limb, have made a few “repairs” on a unit, and suddenly new problems appear, you absolutely certainly do not want to go “repairing” more of that unit until you figure out what you did.

Hindsight is 20/20, but these days everybody has a camera. I recommend taking pictures before you start, so you know where to get back to.

Funny thing is that I’ve been doing this since the days of film cameras, so I never really made a habit of taking photos. I recently started working on a Korg PolySix, and the owner was there to “learn the trade” so to speak. He pulled out his cell phone and started taking photos before I started the repairs. D’oh! I can’t believe I hadn’t thought of that before. Then again, I’m detail-oriented, and I never miss putting things back together because I’ve designed enough electronic circuits that it makes sense. But when you’re just starting out, you really have to be careful.

It’s probably worth studying the schematics and at least learning about how the power supply works, and how it’s distributed throughout the boards. Tall order, I realize, but it’s really hard to fly blind … and dangerous.


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