Guitar effects pedals containing analog delay chips, and a few other types of components, have internal trimpots for adjustment by a technician. For proper operation these must be correctly set, and this is done at the factory. In time - especially with the rough handling that guitar pedals are often subject to - these trimpots can become misadjusted, resulting in distortion, improper operation, or no operation at all.

It is virtually impossible to correctly adjust all the trimpots - called "doing an alignment" - without using lab equipment and the proper procedure. An audio oscillator, oscilloscope, the schematic, PC board diagram, and the test and alignment procedure for that particular pedal are required, as well as technical training and experience. Attempting an alignment without these essentials usually just makes the problem worse - and sometimes more costly to fix!

The most common symptom indicating the need for an alignment is overdrive distortion occurring at too low a signal level. This can also result from weak batteries or an abnormally low power supply voltage, so make sure to check this before sending your pedal for repair.