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.

Friday, April 13, 2018

Air Hogs battle Tracker Hacked

I bought an Air Hogs "Battle Tracker" Nerf Missile launcher hoping to put on my Devastator tank.  It is obviously way too big for that!  However I still hope to interface it to an Arduino or Raspberry Pi and add the ability to track targets perhaps by Infrared.
Air Hogs Battle Tracker
The wired interface appears to be a voltage divider so each button returns a voltage.

Power and ground to the control panel is 3 volts (could be a low battery).  The normal return voltage on the two data lines is 1 volts.  
Pressing the "Fire" button changed PB1 to 2 volts.
Pressing "UP" and "Down" changes PB1 to 1.2 and 1.3 volts
Pressing "Right" and "Left" changes PB2 to 1.2 and 1.3 Volts.

Here is the control circuit board.  I am working on the schematic.

Here is the schematic diagram.  The resistors were measured in circuit so they are off a little bit.  The 51K resistors are labeled "513" as in 51K.  The "22K" resistors are 20K not 22K.  The values must be correct for everything to work.

I rebuilt a LH1500 solid state relay board to interface to the Nerf missile launcher.  I used this same board years ago to control a phone to light message waiting lights....

However when I tapped into the control board two resistors were destroyed.  R33 and R34 are gone.  I need to come up with a better way to interface to the control board.
I have added a 4 pin connector to the control board.  That way I can plug in the control board or the remote control circuit.  I am also rebuilding an iRobot vacuum cleaner to be the wheels for this project.
Air Hogs on iRobot Vacuum cleaner
I plan on butting a Raspberry Pi or Arduino on the red shelf with the batteries and controllers.  Here is the video of it finally working after about 2 months of experimenting.