So, I have a controller keyboard, the MPK 49 that will not turn on via usb. the Display on the keyboard seems like it kinda gets power, but is not backlit at all.

The cable could be bad. Try another cable. USB port problems are also common with M-Audio.

If that doesn't work, try using a 12v adapter to power it on.

Just make sure you don't use both USB and the power adapter at the same time, or you can fry the board.

If it powers on with the adapter then it's an USB issue. If it doesn't, then it's something else.

sounds like dust, if you know some one with an air compresser ask them to give it a blow through, if not then it is down to caned compressed air, if that is not enough, you need to open it, and clean the contacts (DVD cleaner is cheap and good)

Its a lot simplifier than that really.. all you need to do is unsolder the old one and re-solder the new one.. The pins and connectors are standard.

Open preferences. Go to Control Surface tab.
Click Add. Select M-Audio as manufacturer.
Choose Axiom 49

Make sure the ports are set right.

Controls IN Port = Axiom 49 Hypercontrol In
Keyboard Port = Axiom 49 USB A In
Controls OUT Port = Axiom 49 Hypercontrol Out

if it hasn't detected yet then restart Reason.
Make sure the power on the Axiom is on.
If you still have issues the USB port on the Axiom could be bad.

The usual problem of these not being recognized is improper installaation or missing the driver software in the computer. The jacks sometimes appear loose but that can be normal. If you wiggle the jack and there is marginal connections, usually the computer will respond with the USB found and the disconnect tones. If the USB cable has been yanked, then solder could have been broken at the connector. Opening these units one has to be very careful to not damage the cables between the halves of the shell... also keeping track of the screws and type is a must.

To repair a key that has come loose from the pivot, on MUST open the keyboard to get at the mechanism of the leyboard itself. Usually a spring has been displaced or, worse case, a piece of the key pivot is broken off. Be real careful of the ribbon cable tying the two halves of the shell together. Keep track of the screws, type and length to restore them to the proper places.

I have the same keyboard, what do you mean from where it clips on. Do you mean the keys itself are broken? I'm not sure how you did that, but you can contact Akai and see if they will send you a new one. Those keys are supposed to be pressure sensitive and unbreakable. Please rate me for assisting you today! :-) PS I love that little thing!

Make sure the adapter has the center pin as positive and is at least 500ma at 12 volts DC.

This is likely a software you are using with this is either not compatible with those particular controllers OR is not set up to use those controllers. Someplace those need to be mapped into whatever you are trying to control with the knobs.