Boss MZ-2 Digital Metalizer with dead chorus/doubler fnction

[solewheelin]

Hi i'm needing some help with this.
I bought an MZ-2 on reverb with the mode knob not working. It's an analog pcb sandwiched to a digital pcb. The mode knob is stuck in drive function no matter where i set it. I poked every solder joint with a chop stick and couldn't get even a whisper of the chorus and delay/doubler signal. Can't find a loose or cold solder joint anywhere. I was once able to fix an RV3 with a non functioning mode knob by flowing some solder where the mode knob connected to the board so I had hope.. but this issue is different in behavior.
Really hoping to get this working. I'm thinking now it could be the connection between the digital pcb and the outputs but idk.

Here are the MZ-2 service notes if that helps.
https://www.audioservicemanuals.com/b/b ... vice-notes

Thanks

[solewheelin]

Checked everything connected to the outputs and nothing.
Am I SOL here?
I feel like this one hasn't just bit the dust. What could make it just not work?
thanks for any help

[Scruffie]

I'd get an audio probe and start investigating the switching.

[solewheelin]

Thanks Scruffie. Do you mean the switching from the mode knob or the main on-off switch?

[Scruffie]

I'm talking about the FET switches, there's a table in the service manual you posted showing what modes are what.

Seems the digital chip controls the bypass switching so if that works, good bet it's salvageable.

[solewheelin]

Thanks. I wish I could figure out where the FET /bypass switching was so i could troubleshoot that.
Here it is. as it is right now.

[solewheelin]

BTW I didn't have much luck with that service manual. It was meant to help others help me.
Have yet to learn to read schematics.

[Schlatte]

Have you tried measuring if the selector switch is still working correctly? In my experience, 90% of the time it is some mechanical fault, either switches/pots die from mechanical stress or some wire/trace/component breaks from mechanical overstress. Just take you ohmmeter on the unpowered pedal and measure from the center tap of the switch to each pole in every setting and see, if the connections are made correctly.

[whoismarykelly]

BTW I didn't have much luck with that service manual. It was meant to help others help me.
Have yet to learn to read schematics.

You're attempting a top tier repair project so you should probably set this one aside until you learn to read schematics. Then come back to it and you may be able to find a solution reasonably quick.

[solewheelin]

Have you tried measuring if the selector switch is still working correctly? In my experience, 90% of the time it is some mechanical fault, either switches/pots die from mechanical stress or some wire/trace/component breaks from mechanical overstress. Just take you ohmmeter on the unpowered pedal and measure from the center tap of the switch to each pole in every setting and see, if the connections are made correctly.

I will definitely check the paths more closely with an ohmmeter. I mostly just checked for anything loose along the path from the mode switch.

I'm actually pretty good with (most) guitar and pedal repairs. Over 100 success stories, really.
Skeematics though bro. The symbols are not easy. I have tried to learn. Need to take another stab at it.