New Power Adapter

I was noticing some problems with the computer, mostly with the reset circuit. Sometimes, the computer would refuse to reset and I had to turn it completely off and back on again. Other times, I had to wiggle the power wires for it to turn on. When it did turn on, sometimes it wouldn’t actually do anything. The fact that it worked when I wiggled the power wires gave me some clue as to what was wrong, so I measured the voltage at the CPU and got… 2.3 Volts. While technically that is acceptable for some of the components, it is definitely too low for the 555 that controls the reset. Either way, it’s supposed to be 5 volts so something was wrong. I was using the output from the DE0 board, which must not be able to deliver enough current. At first I used this board that came with the lab kit for my computing class. It plugs into a breadboard and uses a DC power supply.

This worked well but I still think I was drawing more current then it was made for, it is just a linear regulator after all. It was designed for a few logic gates and LEDs, not a computer. I looked around my junk pile to try and find a better one. The first thing I looked at was the power supply from an old electronic type writer. I saw a big TO-220 and assumed it was a regulator, but it turns out it was a power transistor. It looks like it uses some simple switch-mode power supply, which I didn’t want to get into. One thing that I knew for sure had one was my Commodore 64. It’s in pretty bad shape and a few of the chips are broken so I didn’t feel too bad about stealing a common part off of it. I kept the heatsink as well. I soldered it together on one of the blank PCBs that I had. The barrel jack was stolen from an old router and I had to bend the pins sideways since they don’t fit into normal holes, but it is still firm enough. Eventually I’ll have to get a better power supply since this one still heats up significantly, even when using 9 volts at the input. Given that my computer uses less components than a c64, all of which consume less power, I think it will be fine for now.