C64 LUGGABLE PROJECT

Power Mounting

As was discussed in the Section 3, Power Preparation, C64 Luggable is powered primarily by an AT Power Supply.

Internally, there are several components that need to be powered. There is the 15" LCD Display, the C64 motherboard, the S-Video to VGA converter and the Mini DC Stereo Amplifier that is used to drive the two front speakers. Ultimately, we want C64 Luggable to be completely self-contained and to be able to be plugged into the wall with a single standard AT power cable.

The AT Power Supply goes a long way towards giving us the power we'll need. It takes 120 volts of AC from the wall outlet and provides multiple connectors and ample amperage at both 5 volts and 12 volts of DC. Unfortunately, this isn't perfect for every thing. The 15" LCD is designed to be plugged into the wall, and has its own AC/DC converter built in. That means we also want to have access to ON/OFF switchable AC, inside the C64 Luggable chassis.

We're partially in luck there. Most AT Power Supplies¹, the older ones at least, have a female AT connector that passes through 120VAC. And, better yet, it switches on and off with the AT Supply's main power switch. Power Preparation describes the splitter and short AT extender cable necessary to connect the LCD Display and still leave open another internal and swichable AC connector. The problem is that that passthrough AT connector is mounted to the back of the Supply, right above the main power-in. What we need is for that passthrough connector to be available inside the chassis.

AC Passthrough

When the AT Power Supply is mounted inside the chassis, looking at the rear, it will be in the bottom left corner. The back surface of the AT Supply will be flush with the back panel and door of the chassis. Internally, the top surface of the AT Supply has nothing but open space above it. The ideal thing to do is to move the rear facing passthrough female AT connector 90 degrees, and have it coming out the top of the AT supply, inside the chassis.

Remove the top/sides shell of the AT Supply by removing the four top facing screws that hold it to the front and back sides of the supply. The shell lifts off with a bit of wiggling. You can see that it is a simple mechanical repositioning to have that top-most passthorugh connector face upwards instead of backwards.

The connector is held to the chassis by two screws, which can be removed to be able to move the connector out of its mount hole. The problem you'll notice very quickly is that there is no way to manipulate the connector, with its wires still connected to it, to feed it back through the hole. Trust me, I tried, because it would have been very convenient.

Instead, it was necessary to unsolder the wires. Take a quick photo of the connector to easily remember how they should be reconnected, then desolder them. The connector then simply pulls out the back of the supply, leaving its wires dangling inside.

These power supplies are Switching DC power supplies, which you can read all about on Wikipedia. Not to be confused with my use of the word switchable, to mean you can press a switch to turn the power on and off, even the passthrough power. A Switching DC power supply is a special trick that was not used by the old-school heavy, solid brick power supplies Commodore always used. These Switching supplies are lighter weight, produce less heat, and more reliable voltage at higher amperage. They are however a bit more expensive to make, probably the reason Commodore didn't use them, and they can fail in a number of unique ways due to their use of more complex components like those giant capacitors.

There is another side effect to the switching nature of these supplies. They switch at a regular frequency that translates into radio frequency noise. The metal case these supplies are wrapped in is not merely for show or for structure, but they also serve as an RF shield. Therefore, as tempting as it might be the replace the shell with a softer, lighter-weight material that might be easier to cut holes in, this is not recommended.

It's necessary then to be able to cut a mount hole in the top shell for the female AT connector. This is a job for a dremel. In fact, without a dremel, I have no idea how else you would produce such a hole. The metal shell is very tough, it's super stiff, quite difficult even to bend. Measure out the size of the AT connector, draw it on the top surface of the shell more or less in line with where it used to be, pushed about 2 inches away from the back side of the supply. There has to be room for the rear panel of the C64 Luggable chassis to wrap around the back part of the supply without covering up or interfering with this top positioned AT Connector.

After dremeling out the hole and filing the edges to remove the metal splinters and razor sharp edges, you can pop the connector into the hole to see where the screw holes should be positioned. Trace them with a pencil through the connector and onto the top shell. Then using a different dremel bit you can bore out the screw holes.

Next you heed to resolder the wires to the connector. An unfortunate result of this is that the top shell is no longer free to be completely removed from the Supply. But I found that there was plenty of extra length of wire tucked in there to be able to easily work and resolder the wires to the connector in its new position. Refer back to your photo, of course, to remember which wires went where.

This will leave the original rear-facing mount hole open. I covered it with a small piece of painted grey wood. I probably should have used metal and I might switch it for a piece of metal. But in these photos it's just a small piece of wood.

That about does it for moving the AC Passthrough Connector. You can then reattach the top shell and your supply will be ready to mount inside the C64 Luggable chassis. I actually think it looks really sharp. The dremel is an amazing tool that makes the job fairly painless. I let mine skip a bit so the top shell got a couple of score marks, which I probably could have avoided had I gone a bit slower. But it'll all be on the inside the chassis.

Rear Panel Mount

The next thing to do is figure out exactly how much space the supply will take up of the rear panel of the chassis. Put the supply down onto the bottom panel and, looking at things from the rear, push the left edge of the supply right against the left side of the chassis. The rear panel itself now requires a three-sided cut out to wrap around the right side, top and left side of the supply.

The left side of the cut out is quite close to the edge. In fact, the piece that wraps down along the left edge of the power supply is only as thick as the thickness of the chassis's side panel, which is 3/4". It is possible that while you're cutting this hole, you might accidentally break off that thin strip. It didn't happen to me, but the weak spots in the pine HobbyBoard are sometimes in unpredictable places. The dirty little secret is that if it does break off, it's not that important, it's not structural. It's essentially just decorative, to give the the chassis a perfectly rectangular shape.

If it were to break off, you could simply screw the piece back into place when the the rest of the rear panel will be screwed on. Then fill any cracks with wood filler and after sanding and painting, it will be completely unnoticeable.

Measuring where the cutout should be is as easy as tracing around the edges of the supply while holding the rear panel in place. However, cutting it out is kind of a pain. You want the cuts to be very straight and have very sharp corners, to look as nice and tight as possible, wrapped around the supply. I believe that I was not using the ideal tools to do this the right way. I actually used a hand saw, which turned out to be less precise than it could have been. I erred on the side of making the cut out too small. But then I condemned myself to an evening or two of vigorous sanding to square it out and make it even and a nice tight fit.

I'm not perfectly sure what tool should be used for making that sort of a drop cut, but if you have such a tool you'll likely have a much easier job than I had.

Once the rear panel is in place, it looks quite nice.

In the above photos you can see how that cut out looks around the power supply, looking through the open chassis from the front. Here you can get a good idea about what I meant above that the top mounted AT passthrough has to sit back a couple of inches. The rear panel is 3/4" thick, and it overlaps the back of the power supply. There needs to be enough space still to comfortably fit the AT Power splitter that will be installed into that top passthrough.

Not every AT power supply has the same external pieces as this one. This one, very conveniently, has a an extra strip of metal out the bottom back side with screw slots. I used this strip to anchor the bottom shell of the AT supply to the bottom panel of the chassis. If your AT Supply doesn't have this lip, I might recommend removing the top shell, removing the inner guts of the supply, and screwing right through the bottom shell and into the chassis. Then replace the guts, put the top shell back on and then position the rear panel. You might come up with another solution, but somehow that AT supply needs to be anchored in place.

From the back, its back edge is held down by the chassis's rear panel, but that alone is not enough to actually keep it in place. There are certainly some other tricks you could pull with a couple of well positioned right angle brackets. Although, you need to be sure nothing will interfere with the placement of the Rear I/O, or Front I/O boards.

9VAC Mount

An AT Power Supply is really handy, for passthrough AC, 5VDC and 12VDC. It has plenty of molex connectors that are very easy to work with and lots of amperage to drive your Commodore equipment. The only problem is that the original C64 and C64c motherboards require 9 volts AC. The 9VAC passes through to the User Port, which might not be a big deal if you don't need it for a special User Port peripheral. But it also regulates the Time Of Day features of both CIA chips. For C64 OS, and for full C64 software compatibility, this is a must have. If memory serves 9VAC is also used in someway by the SID chip too.

There are a few solutions out there. The one I find the most elegant is a board designed by the fine folk who brought us IDE64. This board was designed by Tomas Pribyl (pardon the lack of proper European accented characters). Here below is a quick picture of the schematic, a mock PCB layout, and even a photo of the finished product. It uses a 555 timer and some sort of voltage step down to convert the 12 volts DC to 9 volts AC. Then you can just plug in the standard floppy connector found on AT power supplies, and out the other side wire a fully ready C64 power jack.

I really do feel that this is the most elegant solution I was able to find on the web. I contacted the IDE64 team to ask if they are able to produce them (even one at a time, on demand) but they said it was really just a prototype, and is not commercially available. Unfortunately, it is somewhat above my ability to produce from scratch, especially the PCB. Perhaps if it were available as a kit, I could order the parts and successfully assemble it, but even this was not an option.

The next best solution is a trade off. There are plenty of wall-wart style power supplies that provide 9VAC. Ones from old U.S. Robotics external modems seem to be the most readily available on ebay these days. They take regular 120 VAC straight from the wall and provide a good amp of 9VAC. The downside to these are the weight and bulkiness. But C64 Luggable has plenty of internal room in the chassis, and the weight is already going to be fairly hefty. The advantage to this solution is that there is virtually no skill required in making it work.

I have already described in detail how to prepare the cables, and how to prepare this additional power supply for actually powering the C64. Now we just need to mount the brick. For this I opted for a special velcro adhesive strip. You can find these at most stationary stores, like Business Depot. This stuff is like velcro, but the hooks are made of a tough plastic on both sides. When you press them together, they hold a huge amount of weight, many pounds, before they'll come apart again. And the adhesive on the backside is like super glue. Once you stick it on, you'll never pry it off. Keeping with my goal of modularity, I wanted to avoid the rather obvious move of simply supergluing the 9VAC brick directly to the inside of the chassis.

This velcro-like strip is applied to the back of the 9VAC brick, and then another strip is added to the top of the AT supply. If the 9VAC brick ever dies, I can easily replace it and velcro down a new one. And if I ever want to replace the AT supply, I can easily detach the 9VAC supply and reattach it to the new AT supply.

I played around a bit with the orientation first to see how it would fit in. One thing for certain is that the 9VAC supply fits best directly on top of the AT supply, and is most stable if it is butted into the back and side panels of the chassis. Although there is enough space to mount it horizontally, I didn't like how the cable coming out of it squished up against the AC passthrough splitter.

Instead I settled on mounting it length wise with the cable going deeper into the chassis. It fits perfectly. And you can see how the AC splitter has its short cable that connects it to power. There are now two sources of power, both of which become hot at the same time when the AT supply is switched on. The 5VDC/12VDC from one of AT supply's molex connectors, plus the 9VAC from the U.S. Robotics wall-wart.

These two sources are combined together using the custom cable outlined in the section above on Power Preparation.

Summing Up

That is pretty much all there is to mounting C64 Luggable's internal power supplies. There is one free female AT port, from the splitter that is connected to the top mounted AT passthrough. This will be used to connect to the internal LCD display.

With the front panel held in position, I've shown here a reference ruler to show the relative space occupied and left available. The display sits inset into the chassis, therefore there is more front-to-back space in the area below the display. In fact, there is exactly 8" front-to-back below the display. Behind the display, the chassis has just under 7 1/2" front-to-back. However, the display itself bulges in the middle taking up much of the space.

The AT supply stretches about 5" deep into the chassis, leaving about 3" of space on the front side to house the audio system, and front I/O board.

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Next Section: Rear I/O

1. AT Power supplies are readily available at reasonable prices on eBay from other internet vendors. [↩]

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Last modified: Sep 20, 2022