Turn the amplifier on. Blown or spent tubes commonly cause problem with bass amplifiers powered by tubes, like the Peavey VB-2 Tube Bass Amp Head. Check for this.
Turn the amplifier so it faces away from you. Check for broken tubes or tubes with damaged glass casing.
Check for non-glowing tubes with the amplifier turned on. Non-glowing tubes are broken, and will affect the tone of an amp.
Turn the amplifier off. Wait at least half an hour for the tubes to cool. Jiggle each tube individually with a slight side-to-side and back-and-forth motion. If a tube feels loose, firmly, but carefully, push it deeper into its dock.
Turn the amplifier on and connect the bass. If the amp buzzes, hisses, pops or produces intermittent periods of silence, troubleshoot the input.
Turn the amp off. Jiggle the input. Screw loose inputs in more tightly using your hands or a wrench.
Unscrew tight inputs completely, but do not disconnect them from the amp. Check to see that all wires connected to the input are intact and undamaged. Severed or frayed wires need replacing.
Re-screw the input, turn the amp on and connect the bass. The simple act of unscrewing then re-screwing the input may have jostled the right wire or component to end the buzzing.
Turn a non-initiating Peavey bass amp, or an amp that will not turn on, with the back facing you.
Remove the AC cable from the back of the amp, then reconnect it firmly. Jostle the cable to insure a firm connection.
Plug the amp in and turn it on. If this does not work, turn the amp so that the back faces you once more.
Look into the back of the amplifier to where the thermal circuit breaker attaches to the "on" button on the front of the amp. Check that all wires connecting to the thermal circuit breaker are attached and undamaged.
Damaged thermal circuit breakers or breaker connections will prevent the amp from turning on, and need replacing.