I have a spider III 15W amp that has worked for a year. plugged in last night and it's getting power but no sound. Not even a hum from the speaker. checked everything and it's definitely the amp....

Provided that you're not using any external devices, and plugging the guitar directly into the amp, this sound solely like an internal switching problem. Meaning...it will require service. Chips can get faulty like that sometimes. If you're using any external pedals, remove them and see if it happens. If not...the pedal(s) are to blame.

No, probably NOT a fuse issue here (still lights up, etc.). Are you using the foot-pedal accessory? If so, then unplug it and go direct into amp. Try some headphone via the output jack (sound?) Yes -> GOOD. NO? -> Not so good. May require servicing. Also, check the guitar cord you're using. While unlikely, somehow it might have gotten damaged. Good luck!

Test the amp by touching the tip of the cord you unplug from the guitar and preferably try it with a second cable as well. If at high gain you don't get a loud hum, best to take unit for service. If it hums, then check battery in your guitar. The battery in the guitar is enabled when a cable is plugged in and MANY forget to unplug the cable from the guitar and have a dead battery within a day and blame the amp. This applies to most guitars that have preamps in them... there are some that are "passive" that do not have a battery.

A pilot light means almost nothing other than the power cord is plugged in and hot and the switch is on. In this case, other lights run from various DC supplies so the inout fuse is presumed to be good... NEVER replace a fuse without knowing what caused it to blow or you will usually do more damage within a unit. There are several power supplies and you will typiclly find +/-15 volts on the op amps and 3.3 volts on the processor logic. Unless something simple like the speaker cable falling off this will NOT be a DIY repair. I would look to see if this speaker cable might have fallen off and ALSO check if you get any sound using headphones.

Not a transformer problem... this is likely filter capacitors, rectifiers, and PROBABLY a bad amp chip. Service this before it wrecks the speaker.

The hum MIGHT be directely from teh power transformer vibrating the chassis RATHER than via the speaker. This is an important detail to investigate.

If this has a digital effects processor read on.., I had a SIMILAR problem on a Behringer GX110.

The electrolytic filter cap for the 5 volts of the DSP effects had gone bad. The 5 volts was dipping when the DSP reset and it would repeatedly reset causing a clicking at about once a second. 50 cent part fixed it. The part is a little undersized electrically so is more prone to failure in the unit I have.

That particular one had the DSP as a seperate board with its own 5 volt supply from the main transformer.

Hi there. Sounds like the power amp IC is shorted. Must replace.
Paul

Hi Dan
I wish I could just say what to fix, but you can not do this at home. Line 6 is a great amp and worth the time taking it down to the music shop , to be looked at an give you a repair estimate. good luck keep on rocking in the free world. DFD

output caps. dont beat up your amp. crazy
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