I was experiencing ‘misses’ with my fret buttons. I’d seen lots of mods that replaced the original ‘conductive membrane-type’ keyboard with keyboard switches.
I used my DIY CNC Mill to isolation route a prototype replacement circuit board (Figure 8). The design replaces the circuit board (#1 in figure 1) with a new board, yet keeps the same ribbon cable and connector PC Board (#2 and #3 in figure 1).
Despite using low-profile switches, it was still necessary to ‘hollow-out’ 1.4mm from the underside of the keycaps (Figure 10).
- Fret switches (Figure 4)
- Guitar Hero Manual Fret Button Upgrade PC Board (Figure 9)
- Soldering iron
- Philips Screwdriver
- Torx Driver
I borrowed some images from Guitar Hero Fret Buttons Mod by sonic_dan on Instructables. He did a much better job with photographs than I did. Check out Sonic Dan’s post for great instructions on disassembly to access the PC Board.
Open Guitar Neck to Access PC Board
Refer to Guitar Hero Fret Buttons Mod by sonic_dan on Instructables for details on how to open the neck of the guitar.
PRO TIP: Take some photos before you unscrew or remove the printed circuit board.
Figure 1 shows the neck opened.
- The original circuit board. Held in place with two screws.
- The ribbon cable
- The circuit-board that mates to a connector in the guitar body.
The circuit board (item 1) will be replaced. Items 2 and 3 will be re-used.
Remove the two screws holding the fret-button PC Board. The ribbon cable (#2) and small connector PCB (#3) will just lift out.
Mark and remove the cable
Notice the numbers on the PC board (red arrows). The cable will be re-soldered to the new PC board in this same order, however the wires will enter the new PC board from the “other” side.
PRO TIP: Mark this cable such that you can ensure it is re-installed in the correct orientation.
Although the wiring will enter the ‘other side’ of the new PC board, pins 1-4 and 5-8 are in the same place, so the same side of the cable will still be “up” as it is now.
Unsolder and remove the ribbon cable from the fret switch PC Board. Use care as this is stranded wire and it can get messed-up such that reinstallation can be a challenge.
PRO TIP: The easiest method I’ve found is to pull gently on the ribbon cable and move the soldering iron tip back-and-forth across all the solder joints (think “harmonica”).
The Fret Switch PC Board & Parts
#4 is the ‘underside’ of the fret switch pc board. This is the side you will un-solder the ribbon cable from.
#5 is the flexible, conductive membrane that provides the ‘springy’ part of the switch and makes connection when the fret button is pushed.
#6 is where the ribbon cable is un-soldered.
Figure 4 – The low-profile keyboard switch. Rear view (left) and front view (right)
Schematic and PC Board Layout
I use KiCad to design the (very simple) schematic and PC board. I took care to ensure the wiring matches the existing Guitar Hero board so the same ribbon cable can be used without any modification.
Prototype PC Board
Naturally, since I’m all about CAD/CAM, I wanted to share the prototype board I milled wiht my DIY CNC Router using a technique called Isolation Routing. This allowed me to test the switch spacing, switch mounting holes/pattern and the mounting holes to attach the PC Board to the guitar neck.
Once this was all good, I was comfortable to commit to having some PC Boards professionally made.
Professional PC Boards
I liked the results, so I decided to have a few professional PC Boards made. These are much easier to assemble, thanks to the solder mask.
Insert the switches from the “top” side (the side with the white lettering).
To make sure the switches are installed ‘flat’ with the pc board, put one switch at each of the board, carefully flip it over and solder the two end switches first.
Insert the remaining switches and solder them in place.
The switches will install only one way.
Modify the Fret Buttons
The new Kailh Low Profile Tactile switch sits about 1.4mm taller than the old ‘membrane’ type switch (#5 in figure 3).
To adapt for this, I needed to mill-out 1.4mm from the underside of the fret buttons (B in Figure 10).
I have the luxury of a small mill, so it was easy for me. Whatever method you use, be sure to make every button consistent or you might end up with an ‘uneven’ feel to the fret buttons.
Cut too shallow and the button stays pressed, too deep and the button may not activate at all. Both those should be fixable!
Another possibility might be to trim the 1.4 mm off of the mounting posts and the small pegs that support the back of the PC board. I didn’t try it, so I can’t comment if it’s harder or easier.
8. Put the modified fret buttons back in place. Use the same screws to retain the new PC board.
9. Verify the ribbon cable is in the original orientation.
11. Route the cable and re-install the connector PC board.
No changes or modifications are required to the neck of the guitar. The only mods are for the underside of the fret buttons (Figure 10.)
When I opened my guitar neck, there were already several holes in the ribbon cable (#10). Not sure if that was intentional or accidental, but either way it had no impact electrically.