Armdroid Power Supply Pictures

The power supply that came with the Armdroid was just a big black box that weighs about five pounds with a switch on the front and two banana jacks on the back. I plugged it in and tested it one day - something is broken, because no power came out the banana jacks.

The back of the power supply is dominated by a large heatsink containing two 2N3771 power NPN transistors.

Inside the unit there is a large transformer (largely responsible for the weight), a circuit board balanced on a large 16000µF capacitor (am I reading that right?), and various point-to-point components. There is a large 2200µF capacitor hanging from the banana jacks, and two 0.1Ω 5W power resistors connecting one of the pins of the 2N3771’s to ground (which are wired in parallel).

Pulling the capacitor out of the clamp allowed me to get a shot of the underside of the circuit board. This photo also revealed the half-bridge rectifier that turns the AC from the center-tapped transformer into DC.

Here’s a zoomed in shot of the circuit board. In the socket is a LM723CN power regulator, on the heatsink a TIP29 NPN transistor, and the third thing is a 2N6509 thyristor.