Acoustic 370 strange output

[Axtman]

Does anyone know what would caust this strange output waveform? I put a sine wave into it. What should I check first? I will probably just trace the waveform through the circuit anyway.

[DrGonz78]

Trace the sine wave through the circuit and determine which point you notice a major change. Find that location on the schematic and start testing voltages of any transistor junctions. In fact I would have already checked the main power supplies. But ultimately we need more specific information about what is going on with the amp. Is this with a load? What is the voltage of the input sign wave? Don’t forget to tell the amp to behave itself. In other words it could be a bad connection somewhere.

[Axtman]

Here's the schematic. acoustic-370-schematic.pdf

I like Accoustic Control Corp. amplifiers, but they are a pain to work on. It's like they purposely make it difficult to get to components. I am trying to figure out how to get to the eq board to replace a slider and I may have to unsolder the transformer and remove the big filter capacitors!

[Axtman]

The amp has an 8 ohm load and an input signal of 500 mv.

[g1]

If the signal looks fine with no load I would suspect something in the driver stage (assuming you have checked the output transistors and their emitter resistors).