EHX9 series - stuck on one voice

Stickman393

Well-known member
A'ite.

I've got a question here. I've got a Mel9 pedal that is stuck on one voice. The rotary knob doesn't do a thing.

I've been doing some research. This is some kind issue with the EEPROM as far as I've been able to suss out. There's a 10 pin header on the PCB that provides access to the EEPROM, and from what I've read it's fairly easy to grab the program with the right software and interface.

I *really* don't want to send this thing into EHX for repair, because I'm stubborn and want to learn.

Diy stompboxes has a thread started by our own @bean that developed into a guy who was able to rip the programs from all the 9 series pedals and install a board in one that allowed for every 9 series sound in a single pedal. Which is cool as hell, but way beyond what I'm interested in. I just want to get mine switching between its existing voices again.

Link here:

So...there's *gotta* be a way to figure this out, right? Rip the EEPROM and reset? Find someone who has a working rip of the EEPROM and load it? Replace the EEPROM and load the program on it? Something?

Anybody here got any advice?
 
that line is very picky about power.
Are you using/do you have the ehx supply?
I've seen multiple instances of people using *good* isolated supplies that screw with them. Maybe some weird ground noise messing with the digital?
 
Nah, definitely not PSU-related. Tried with an EHX supply as well as my CIOKS. No dice. Was reading up on that, apparently has something to do with a slow rising edge on certain PSUs. Causes the DSP to crash on boot.
 
Looks like there's 0ohm resistors on each leg of the switch. Maybe check those. Looks simple enough
A likely 5v/3.3v line getting switched and return straight to the AD brainbox.
No muxing or anything.
Find you hot pin. If there's no hot pin, then the source signal is bad.
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