See how to repair your broken guitar effects pedal. Use our in-depth guide and little care to fix your pedals without resorting to expert attention
Next, look at the battery clip. Lots of apparent pedal faults arise from poor clip contact. Gentle torque applied to the clip with the battery held firmly might reveal a small movement (pic 3). If it does, pinch the sprung terminals of the clip and the battery gently with pliers to the point where the clip requires a firm press-fit. Covered wire-breaks, where the conductor is fractured but the insulation looks okay, can be revealed by a simple pull: a good wire can take quite a lot of force. We assume you’ve checked the battery (in a working pedal, or by the well-known tongue-tip method) or at least know its recent history.
All being well, fit a good battery and have a sniff round the circuit with a digital multimeter set to DC volts. Insert a jack, in this case to the output, but more usually to the input, to power the board. This simple switching method usually works by interrupting the negative battery connection to the board and making it via the jack plug barrel (sleeve) when this is inserted. Colorsound pedals use a terminal wired to battery negative, contacted by upward deflection of the jack’s sleeve terminal – but the idea is the same. Checking this circuit is always good practice.
It helps to have the circuit diagram to hand (most classic pedal circuits can be found on the net at sites such as Harmony Central). From it we see that the Tonebender comprises three single-transistor common-emitter amplifier stages. These are checked by clipping the black probe to any ground point and using the red to probe each of the transistor terminals (pic 4). In normal operation this will confirm that the collector (right-outer terminal in this type of transistor) is at about half the battery voltage, while the others are much lower – the emitter (left outer) at a few mV above earth, and the base (centre) about 0.5V more positive than the emitter. This small difference between the base and the emitter (Vbe) is the pole star of transistor operation, and base-to-emitter shorts are a common failure mode. It’s not too much to say that normal V be validates a transistor regardless of other voltage abnormalities that may well be caused by component failures or (more likely) disco’s. A collector voltage at about battery or supply potential usually means an open-circuit transistor or a lack of bias.
Fixing a pedal, pedal servicing, broken guitar pedals, maintaining a guitar pedal, battery issues,battery problems,Tonebender,