I have a fender mustang I V2 amp I've been using since January of 2015 and recently I took it out to the garage to practice with a drummer, and it was raining, but the amp was far away enough to the rain to not be damaged when outside, but I brought it out and it's currently only making a humming sound like the gain when there is a cable plugged in without a guitar connected. I attempted to change cables and guitars to see if it was an issue with that, and the problem still persisted, so I was wondering could anyone help diagnose the issue?
Last edited by knoxsw at Sep 16, 2016,
Sure, let's start with some things.

Is there a firmware or software update you can run?
Can you manipulate the hum by any means? For example, does it get better or worse with the volume, master, gain, EQ, effects, or plugging a cable in? Does it ever cut in or out?
All of the lights coming on and acting as usual?
Get anything when you plug into the "aux" in?
Roc8995 I've come to the conclusion that it's the input jack because, the Hum comes out of the speaker fine, making me think it's not the speaker (I also don't have an aux cord on me ATM). The EQ knobs do alter the tone and gain, and the lights are on which means that's probably okay, but there isn't any change in the hum when I put in the cables with both of the guitars I have (even when I just switched the cables I had for new ones) leading me to believe it's an issue with the input jack.
I agree. The good news is that it should be cheap and easy to replace. Hopefully it solves the problem.
Let us know how it goes. I wonder how hard it is to get at the input jack of this particular amp. I haven't opened one myself.

As always, be careful inside amps! Dangerous zaps abound...