Hello, everybody

I've been having issues with my Fender Mustang I... it only emmits a buzzing sound, whether or not the cord or the guitar are plugged in. When I plug the guitar into the input or ftsw, nothing changes. Plugging in the headphones just makes the buzzing sound come from them.

I really need help, desperately. I've removed the back part of the amp, but I don't see any disconnected wires or anything similar.

Thanks in advance!
Is your Mustang a MI (V2)?

Is so, I would first suspect some sort of external interference in the AC Power or perhaps Radio Frequency Interference (RFI) nearby.

If the first case, a quality power Line Conditioner or Uniterruptible Power Supply (UPS), can often resolve the problem. If RFI is also contributing to the problem, the best solution is to increase the distance from (or remove) the offending item (florescent lights, transformer, motor, wireless router, etc.)

Another troubleshooting method is to try your Mustang on another circuit at an entirley different location. If the problem is no longer present you know your amp is fine and it is your AC wiring or RFI at the first location.

The Mustangs contain several High Gain Amp models in some of the Presets. Some of the on board FX can also hammer the front end with increased levels. Check to be sure you don't have a Preset selected with its Gain and Volume Set at or neat Maximum and that the Preset doesn't also have any FX enabled that are configured with their Level, Gain, Drive set at or near Maximum.
Mustang v2 III/IV●EXP-1●FUSE●REMUDA●Yamaha THR10C
Epi LP Florentine Pro●LP Cstm Pros●LP PlusTop Pro●Sheraton-II Pro
Cstm Strat Vntg Noiseless●Guild D-55
So Creek Cables●BOSS RC-1●RS7500
D'Addario Strings●Vari-Grip●Planet Lock Straps