Klipsch Promedia V.2-400 V4.1 V2.1 And V5.1 Amplifier Repair

Posted on Feb 6, 2014

I began tracing the BASH amplifier circuit for my V. 2-400. The following schematics are my best effort to document what I found. I have also described design defects I have found and what I am doing to improve them. Evan Shultz spent an amazing amount of time tracing the circuits for his ProMedia V4. 1 and V2. 1. This tracing included removing some components to check their value and replacing them.

Klipsch Promedia V.2-400 V4.1 V2.1 And V5.1 Amplifier Repair
Click here to download the full size of the above Circuit.

If you think this is not an amazing amout of work, you have never tried it. After generating schematics of the ProMedia V4. 1 and V2. 1, Evan moved on to the ProMedia V5. 1. Miguel Mejia provided a V5. 1, and Evan bought another V5. 1 off E-bay. So now we have the complete Promedia line from V2. 1 to V5. 1, giving you the customer support that Klipsch would never provide. The BASH amplifier is not as complicated as it first appears. AC power of 117 volts is rectified to 156Vdc on the Input-Output board, and then goes to to the DC-to-DC converter. The converter drops the 156Vdc to +/- 30 Vdc that goes to LM340 and LM320 discrete IC regulators on the Input-Output board. From these regulators, the audio IC preamplifier stages get powered up. The converter also supplies a fixed 60-Vdc to what Indigo calls a Digital Converter. The Digital Converter is the heart of the BASH amplifier. Voltage to the power amplifiers is kept just a few volts above the amplifier`s output swing voltage by an audio processor hybrid pulse-width modulating a buck step-down converter. A buck step-down converter operates by applying short pulses of high voltage to an inductor in series with its output load. These pulses flow through the inductor, which builds a magnetic field. The collapse of the magnetic field between pulses keeps the current flowing at a constant rate into its load and back to the inductor through a diode. The voltage across the buck...

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