EHX9 series - stuck on one voice

[Stickman393]

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:

A tale of two 9's

A tale of two 9's

www.diystompboxes.com

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?

 

[jwin615]

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?

 

[Stickman393]

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.

 

[jwin615]

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.

 

[jwin615]

https://www.mouser.com/datasheet/2/609/ADSP_BF592-2955848.pdf

 

[jwin615]

@Stickman393 does the above help?
It's not an hour past bedtime so I can expand if needed.
Edit: also, not sure if that's the same DSP as yours. EHX could have changed them over time. It's just a gut shot I found online.

 

[Stickman393]

It does, I'll do a quick check of the switching. Same DSP, Analog Devices (or as I like to refer to them, after working in one of their buildings a few years back and spurred by my work phone's unfortunate shorthand for the job name, "Anal...vices") 592K.

Mine's a Rev C. Could probably do the all 9 mod, honestly. Might one day if I get more into digital.

Bought this thing for a song a while ago assuming that it was an easy fix, and was immediately stumped. I haven't actually opened it up again since today. Stumbling upon that tale of two 9's thread got me curious again.

 

[Stickman393]

Well...son of a bitch.

Seems like I'm getting 3.3Vdc on all legs of the switch except for Pin 1 regardless of where the switch is positioned. Pin 1 is 0V to ground.

Those results make me think that this fucker is supposed to pull the signal low, which means that the switch itself isn't actually shorting contacts. It probably lifted off its contact pad.

Which, if correct, means that it is in fact a mechanical issue with the selector switch.

I suppose i can just short a leg to ground and see if it changes the voice to test it out.

 

[jwin615]

Hmmm. An interesting way to go about implementing a switch.

 

[jwin615]

Oh.no. I just can't comprehend words. nm

 

[Stickman393]

Honestly: I messaged EHX a while back about this and specifically asked if the switch was generally understood to be the cause. I then asked if the SP9T replacement switch they offer on their site would be the solution.

They told me that the part was unavailable for purchase and to send it into them.

Which I found to be extremely annoying. But I also took at face value that the switch was not generally understood to be the issue when this problem pops up.

Which only goes to reinforce an axiom that I've learned to rely on over the years at work and in life:

Technical support is fucking useless.

 

[jwin615]

Honestly: I messaged EHX a while back about this and specifically asked if the switch was generally understood to be the cause. I then asked if the SP9T replacement switch they offer on their site would be the solution.

They told me that the part was unavailable for purchase and to send it into them.

Which I found to be extremely annoying. But I also took at face value that the switch was not generally understood to be the issue when this problem pops up.

Which only goes to reinforce an axiom that I've learned to rely on over the years at work and in life:

Technical support is fucking useless.

It would appear the real tech support guy/gal was on vacation.

 

[jwin615]

See post 4

 

[Stickman393]

Jesus that just broke my brain.

I think I need to grab a DIY stompboxes account and message that guy.

 

[Feral Feline]

The linked post#4 grabbed my attention — I've got a Super Ego.


Every 9-series' sounds in one pedal sounds good to me.


Kind of like how Digi2T & Co did the XP-ALL (and somebody else who called their version the XP1000)...


Hope you manage to sort out your Mel9.

 

[Stickman393]

Whelp: resolution!

I yanked out the old 1p9t switch and tested it outside the circuit. No continuity between any of the pins, no matter where I set it.

The replacement switch I sourced from EHX shorts from the common terminal (1) to the switched terminals (2-10). It shorts the 3.3v pin voltage to ground, and this is how the pedal switches voices.

I gotta fuck around with it a little more: for some reason the signal I get from this little box is a little distorted. I'll poke around and see if I can find the source. But in terms of being able to switch voices: it's alive!

Never seen a switch go totally open like this before. Hopefully it doesn't happen again. But now I've got...like...nine extras. Fucking EHX and their minimum order cost.