Tuesday, December 20, 2011

Today I modified my Rock Band 3 keytar that I use in The Glowing Stars. Unfortunately the project wound up significantly more limited than expected. The keytar controller has three big issues from a performance MIDI perspective (the perspective from which I approach it) that I went into this aiming to fix:

1. Backwards pitch bend ribbon (towards the keyboard is bend up)
2. pitch bend ribbon is set to modulation control by default - only by holding down the adjacent button will it output pitch bent info, but holding down the button makes your hand nearly useless in the process.
3. No damper button.

Not knowing what to find, I venture forward.

Straight ahead disassembly, but the final screw is hidden under this rubber stopper which must be pried out. Presumably somebody decided that if you're vain enough to be playing a keytar - even in a video gaming session - you would care about hiding only this one screw - but no more.

While I'm at it - if you disassemble one of these yourself, take note that the screws on the keyboard edge of the unit are shorter than the rest. I wasn't paying attention and almost drove a hole right through the plastic...

These tiny screws are held up from the board by a variety of slightly different spacers. If you don't get them put back together correctly, the "whammy bar" or whatever button won't correctly. The goal here is to bypass that button anyway, but why make things uglier than they need to be? Besides, it's a minor puzzle.

A close up of the well labeled solder points that are connected when the front panel button is pressed. Here (and in the previous shot, which was shown out of order), they're already wired to a submini switch which I'll install on a drilled hole in the case. When the switch is closed, it puts the ribbon controller in permanent pitch bend mode, and returns the unit to normal operation when it is open.

The final result. Relatively innocuous modification. I decided to place the switch here because it is out of the way, but still available while playing.

As for the other things I had hoped to fix;

The ribbon controller seems to consist of about 8 touch pads and a micro controller which I'm assuming generates data based on which touch pads are pressed. Not a particularly high resolution device. I wasn't willing to get into it on my only keytar, but once I grab a spare, I have hopes for cutting all the traces on the PCB and re-connecting them in reverse to fix the pitch bend. A little bit obnoxious, but I don't see why it wouldn't work, as long as I can avoid burning out the SMD chip.

The keytar does provide an 1/8" jack for control pedal functions. According to the manual it can handle one analog expression pedal (no details provided) and one "digital stomp switch" which functions as a damper pedal. Now if there's a standard for "digital stomp switches" I'm not aware of it, maybe someone can enlighten me? But for the moment, I find my hopes of a damper control on the back of the handle (similar to Roland's AX series of keytars) dashed.


Unknown said...

Hey, great article. A friend and I were looking to do similar mods on our keytars as well. While experimenting, we plugged a regular Roland sustain pedal in to the pedal jack and it worked well. Maybe you could wire the original mod/bend switch to the terminals for that jack.

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