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.


NikGti said...

Replace the 4 capacitors nearly 2SA1930/2SC5171 from 101/1Kv(100PF), to 22PF/1KV or 33PF/1KV.
With 100pf the amplifier from 10Khz and upper has not amplification, falls dramatically. This capacitors they are used for cutting the very high frequencies. The 100pf is wrong.
The 22pf cutt the upper from 23KHz and the 33pf upper from 21KHz.

chris g tucker said...

There are literally a Zillion of these old Audio Centron Amplifiers here in Tampa. They can be bought in working condition all day long for very little money!
My friend has the large 1600 Audio Centron Amplifier, and it works and sound very good.
Yes, it is big and heavy, but he uses it as a Home Stereo Amplifier, so never has to carry it around.
We replaced the old Power Supply Caps. Found some cheap new ones on Ebay that were Chinese. LOL, this old amp of his may be good for 20 plus years.

Anonymous said...

As long as you watch the ohm. Make sure its correct especially if it is ran bridged mono. Great hot bass amp! They drive! I run 2 jbl 4550 swooped bass cabs with each housing dual 15 inch 2225 j series woofers and they sound amazing ! That old audio centron just keeps pounding. I did install 2 new fans one in front and one in back because i run it for 8 hour shifts .