If you hear a pop when you turn it on and the squeak when turning off most of your amp is probably working.Depending on whether it is a tube or solid state amp there are several things to consider some being as simple as a deadLED or bulb in the pilot light and a defective input jack to as complicated as a dead power supply to the preamp circuitry. If you are not familiar with safety procedures and electronic trouble shooting and have no test equipment and the schematic you might be better off having it serviced. Here is a link to a troubleshooting guide:http://www.geofex.com/ampdbug/ampdebug.htm A lot of the info can be applied to solid state amps. Hope this helps.
The power indicator light does not turn on when the amp is turned on, and no sound comes from the speaker (which is fine) or the headphone jack. It makes your average popping sond when it is turned on, and when you turn it off it make a squeeking pop sound.