10 June 2019

Commodore Project 64 Part 6: The Power Supply

I wasn't planning on doing another P64 post until I did something interesting and worth sharing. But two of my Commodore 64 power supplies died on me and the third isn't putting out the correct voltage. This left me with no means of using any of the machines for a few weeks until the new one I ordered arrived.

Of course I can't live with that, so I thought back to a video from Perifractic's Retro Recipes in which he built a cheap and simple power supply.
This blew my mind because the original C64 PSU is big and ridiculously heavy. I guess electrical technology has improved over the past thirty years.

So I've been planning on building one of these for a while but hadn't had a reason to bother with it until now. I even had the components I would need already, so I spent some time analyzing some things Perifractic didn't explain clearly and doing a little bit of my own research elsewhere to figure out exactly what I needed to do.

Extension Cord with 3 plugs
9V AC Wall Adapter Transformer
5V USB Wall Charger
4 Solder Seals
USB cable
Original Commodore 64 PSU

I've provided links to three of the items, but I bought the extension cord at Wal-Mart for around $2. Be sure the 9V adapter is AC because adapters seem to usually convert to DC. You don't want that. For the USB cable, you probably have one laying around somewhere that you don't use for anything.
Remove the bottom of the C64 PSU. Some of them are held on by screws but this one had to be pried off with a knife. Not a big deal because I don't care about this power supply anymore.
Disconnect the cable and its wires that connect to the C64. That's all we need for the new power supply.
You'll have four wires, so expose the insides with wire strippers or whatever you use to strip wires. Using a multimeter, find out which wires go to which pin. I made a diagram to keep track of mine and you should do the same.
This diagram is for illustrative purposes only. Please do not rely on it for your PSU because the colors of the wires vary. 
Here are all of the components laid out. 

Cut off all but a few inches of the transformer's cable and expose the wires within. Mine were white/black and black. Both are 9V, but I didn't want to take any chances and looked at Perifractic's video closely to find out that the white/black connected to pin 7 and the black to pin 6.

Do the same with the USB cable and expose those wires. My wires were red and white. The red is 5V DC and the black is the 5V ground, so these connected to the brown and blue wires, respectively.

Using the solder seals, I connected all of the wires and then used a heat gun to seal them together. A lighter would also work just fine.

The end result isn't pretty, but as long as it worked, I'd be happy. I plugged the new PSU into the wall and tested the pins. They gave me the readings I wanted, so this was looking promising.
Out came what I call my Sacrificial 64. It has some minor problems with its display but otherwise works fine. Any time I want to try something new with the hardware, this is the machine on the front lines. If it was ever damaged by any of the tests, I'd definitely fix it, but I don't want to risk my other machines.
I plugged the new power supply into Sacrificial 64 and plugged the machine into my TV. I turned on the power and saw that beautiful red light and didn't smell anything burning! 

Next I turned on the TV and switched to channel 3.
Perifractic you're a genius. I don't know if you'll ever see my blog, but from the bottom of my heart, thank you! 

But I couldn't just stop there, of course. While Perifractic used a pre-made project case to hide the ugliness, I wanted to keep to the Commodore aesthetic as much as possible. So I got to work in TinkerCAD.
 Many hours later, I had something worth printing. So to the 3D printer it went!
The top portion of the case took 18 hours to print and the bottom another 4. This was easily the biggest 3D print project I had ever tried. Here are the results, with the original for comparison.
It's a tight fit for all of the parts, but that's a good thing. It won't rattle around too much. 
I mistakenly placed the circle feet incorrectly, but it's good enough for the first version. Fixing that for the next will be easy. I also need some kind of label showing the input and output voltages.
And here's the top view. I'm happy with the overall look, but I had to print the top upside-down with supports. Getting those out was a huge pain and left a lot of weird marks. The next version will probably be in three pieces to allow smoother printing. This picture shows the difference in size between the original and my version.
And here's a slightly more pretty shot of the old and the new. With the exception of the messed up top, I doubt anyone would know immediately that this was not an original Commodore 64 power supply. 

For a first attempt, I give it a not bad out of ten. Having a physical thing to examine will make future versions easier. The original PSU had a grounding prong, but from what I've been able to figure out, it's not that important. With some tweaks I'll be able to add a grounding prong just to be on the safe side. Until then, this is fine.

I'll probably convert the other two PSUs I have using this method at some point in the future. This project cost me less than $20 while the new PSU I ordered was close to $100. I don't regret that purchase for reasons I'll explain in a later post.

If you're interested in building a PSU of your own, let me know!

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