Tuesday, April 17, 2018

Audio Centron RMA-1600 Audio Amplifier rebuild

I have been rebuilding aa Audio Centron power amplifier.  The TO-3 transistors were bad and it was cheaper to replace all of the "guts".  The power supply is positive and negative 80 volts.  So I searched eBay for a amplifier board that can handle that voltage.  This is what I found:

1PC NJW0281/NJW0302 450W+450W HIFI Stereo Amplifier Board Assembled AMP Board

Description :

This is completed board.You don't need solder it.
4 Pair MJW0281/MJW0203 for one channel.
so one board has 1 6pcs transistors.
Power supply: DC 45V to 85V
Power: 2X450W (-85V @ 4 Ohms)
PCB size: 259 * 73MM

However if I was to do it over I would use a PR-800 amplifier board.

Here are some picture of the amplifier rebuild.  We used an old heatsink and tapped the necessary holes in it.  The heatsink is upside down while we connect the wires to it.  The power and speaker posts fit the connector pins from an ATX power supply.

Here are some more pictures showing the progress.  We are now testing it at low levels.  The input jacks go through the front volume controls to the amplifier inputs.  The front panel is now powered via a 1K 10 Watt resistor.  The signal inputs to the front panel go through 33K resistors to the speaker outputs.

Its nearing completion with the installation of a speaker protection relay board.  That required that a 12 volt transformer be added next to the main power transformer.

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