How I Fixed My GNX4 for $2, part 2

So, I discovered the problem with the GNX4 wasn’t the cord, but the USB port itself.  So I needed to decide whether I’d be forking over bucks to someone else, or if I’d take a stab at fixing it myself.

Over the last two years I’ve acquired a fair amount of electronics experience through building a Theremax and by building two Gristleizer effects boxes, not to mention rebuilding a bunch of computers and various other hacktastic adventures.  So I figured what the hell, I can do this.

First task then was to open the GNX4 and see what was inside.  The top of the housing is attached to the bottom with a bunch of little hex screws, the little black circles on the case as seen below.  I finally found a driver that would fit, and then disassembly of the case was quite easy.

I carefully lifted off the top , which contains all the controls, LEDs, and other aspects of the so-called GNX4 user interface.  All that stuff is attached by two ribbon connectors to the bottom circuit board, which contains all the inputs, outputs, and our USB port.  I discovered I needed to detach the jacks and inputs to remove the board from the bottom of the GNX4 housing.  A simple matter: I just needed to unscrew the nuts that hold the jacks snug against the housing.  I made sure to put the hex screws and those jack-nuts in a safe place, then.  The touchpad of my Logic control surface seemed as good a place as any:

Now I could remove the sound circuit board without messing with the ribbon connectors.  It looked like this:

From here I was easily able to locate the precise location of the fucked USB connector. Not a great picture, but here it is from the top:

Having located the port from the top, it was a simple matter to find the solder points from underneath the board.  There were two large solder points, then four tiny ones.  If you play “Where’s Waldo” with the photo below, you’ll find it:

So now I unsoldered the bad USB port and removed it.  Hip hip hooray.  Here’s the culprit, on the right.  You’ll notice the complete absence of a middle, in contrast to the good USB port (white) right next to it:

You can't get there from here.

You can’t get there from here.

Part 3, coming right up…



  1. Hey
    My gnx4 is mess up . when you turn it on it just goes to verson 1.3 and stays there
    I tried to do a reset but it doesn’t work. But before my Gnx4 pedels 1,3 stopped working and it did the same stuff that yours did with the USB shit.

  2. I have the exact same problem with my USB jack in the GNX4. Anyway you could give me some more info to try to do the same as you?

  3. Dear, my GNX4 starts and goes upto version 1.3 and then restarts and this goes on and on and on….

    I live in area with no dealers around. The digitech support says I have bad ribbon. can it be easily fixed?

  4. Hello. I’d like to know which hexagonal screwdriver did you use to open it up, please. Thank you so much!

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.