Anyone there super familiar with MIDI controllers - Page 1
Forum section: electronics / repair

author: gooseEL34
author_rank: Regular Contributor
timestamp: January 24, 2015, 09:22:04 pm
content: Have a M-Audio Keyrig 49 which is a VERY basic 49 key midi keyboard controller (USB out).49 keys1 EDIT MODE button2 OCTAVE buttons1 VOLUME slider potentiometer2 Thumbwheels (pots with wheels on the shafts to be rotated with the thumb)Bought it used and the volume slider does not work at all.The other problem is that the PITCH BEND wheel does pitchbend correctly, but it ALSO acts as a volume wheel(thus, rolling the wheel forward increases both pitch AND volume and backwards decreases both pitch and volume)I used MIDI-OX input monitor to view the midi data coming in. All keys function correctly.Anybody know a likely cause of this? Inspection of the boards show no apparent burnt damaged or loose parts.I am assuming it is something in the main IC, but before I toss it (cost me only $20US), I thought I would throw it out there.ThanksTim

author: gooseEL34
author_rank: Regular Contributor
timestamp: January 24, 2015, 10:50:57 pm
content: Found the solution.....(this is what I posted to the interwebs for another guy who had the same thing happen)I have the answer...It lies in a crappy volume fader potentiometer.I opened the unit and started troubleshooting. With a digital voltmeter, I took readings of the pitch wheel potentiometer as well as the modulation wheel and the volume pot. I discovered that the wiper of the 10kOhm volume potentiometer was not connected to the wire and plastic connecter that meets the main board.Sure enough, I opened the potentiometer by bending the little arms on the outer chromed case and exposed the innards of the slider. Sure enough, the little brass or copper spring fingers that make contact with the resistor strips on each side had not been making contact. I bent them downward and reassembled the switch by bending the case fingers back in place and whalaa! Works fine!!So, if you are not comfortable with getting inside the switch, you might be able to find a 10kOhm fader style potentiometer at Radio Shack and it may fit the holes in the board. If not, you can eliminate the board entirely and just find a small piece of PCB board, mount any 10kOhm slider to it and cut the pigtail off the old board and make the connections to the three slider connections (wiper and each end of the fader's strip). You could even drill a 3/8 inch hole in the top plastic piece and change the slider for a rotary pot and knob.... Just use any 10K pot (I believe the taper is linear not audio, but I am not sure)

author: obiwanjacobi
author_rank: Super Contributor
timestamp: January 25, 2015, 07:35:34 am
content: I would think the volume fader is indeed linear. It's position has to translate to 0-127 digital value. The audio-taper is done in the synth, I think...How's the pitch bender?

author: gooseEL34
author_rank: Regular Contributor
timestamp: January 27, 2015, 09:51:59 pm
content: The pitch bender functions nicely. I downloaded MIDI-OX and was able to play piano on the computer. There was some latency issues, but with the input monitor, I was able to see all the midi info transmitted by the unit. For all practical purposes, it is fixed.

author: obiwanjacobi
author_rank: Super Contributor
timestamp: January 28, 2015, 09:19:41 am
content: Nice!