If the power amp is dead, pull the output transistors and test them with a multimeter’s diode mode. The schematic will tell you if those transistors are NPN or PNP. Replace in matched pairs. After soldering, use the trimpot (often labeled VR1) to set bias according to the schematic’s exact millivolt reading across R85 and R86—usually between 3mV and 8mV for Class AB operation.
Using your multimeter, measure DC voltage at the power supply filter capacitors. Refer to the schematic for expected voltages. If +45V is reading +12V, your rectifier or transformer primary may be bad.
For decades, Peavey has been synonymous with rugged, road-worthy, and surprisingly versatile bass amplification. The Peavey Max 115 stands as a prime example of this philosophy. This 1x15 combo amplifier, often found in rehearsal studios, small clubs, and bassists’ personal practice spaces, is beloved for its punchy low-end response, simple control layout, and near-indestructible construction.
The Max 115 has an effects loop or preamp out/power amp in jacks. The schematic shows the switching jacks. Use an external preamp to feed a clean signal into the power amp input. If it works, the problem is in the preamp. The schematic then guides you through op-amp supply voltages (pins 4 and 8 of TL072s, for example).
In this deep-dive article, we’ll explore why finding the correct , unaltered schematic for your specific Max 115 version is critical, what secrets the circuit diagram holds, and how to use that exclusive technical data to perform effective repairs. Before we look at voltages or transistor biasing, we must address the single biggest hurdle in repairing a Peavey Max 115: Peavey revised this amplifier multiple times.