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Alesis RS-150 Reference Amplifier

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  • Alesis RS-150 Reference Amplifier

    Hello everyone!

    New here, hoping someone can help me out with my repair here. I'm currently working on an RS-150 reference amplifier by Alesis. When I received it, there were a couple of charred 1watt resistors and a blown capacitor on the power board. I replaced those, along with the other components in the vicinity.

    This is a stereo amplifier that has two separate boards for each channel. One of the channels is working perfectly, loud and clear. The other is about 1/4 of the max volume of the working channel. I've probed voltages on all of the regulators on both boards, and they match. I've also checked all caps (both electrolytic and poly/ceramic) for shorts and leakage with both the multimeter and scope. All transistors (including the discrete opamp triple-darlington transistors) check out okay. Diodes check out okay. Visual inspection of all other components checks out okay, as well as level pots. Input jacks are good, I even replaced the NE5532 input opamp on the bad channel, thinking it had something to do with the input stage.

    I cannot source a schematic for this amp, and my only reference is the owners manual on specs.

    I swapped boards with both channels on the power board, and it is definitely the one board that is faulty. I wanted to swap the discrete opamp boards to see if that was the issue, but one is specifically populated with components for bridging the amp.

    Thanks,
    Chuck
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