The “Sixty Clone” C64 Project

When building any electronic project from scratch you will of course need the components to go with it. Even though I already have most of the required components in my stock, I chose to purchase a complete kit as this would ensure I had matching resistor manufacture for each value and the rarer and harder to finds parts like the Joystick port connectors and the power connector and switch are included.

All the necessary logic IC’s and power supply components are also included but I changed a few of these for better values and because of a strange higher than normal voltage reading (More on this to come)

Also, as seen on the packaging I got all these parts from ‘Run Stop Re-Store’

Close up of the joystick ports, edge connector, switch and power connectors

I started this build with placing and soldering the connectors in place first. Most people would usually start with the smaller passive components like resistors but I just fancied starting with these.

The second picture is a close up of where the power circuitry components will be placed.

Next I installed all the passive components which are made up of resistors, bypass capacitors and network resistors.

I try to keep all the resistors facing the same way so the colour bands are in order and it also looks more professional but there’s always one that slips past and ends up facing the other way. Has absolutely no affect on operation but just annoys me.

Next we have some of the power supply components fitted, the capacitors, bridge rectifier and fuse. The two large empty pieces at the bottom are for the voltage regulators, I haven’t fitted these as i have changed the original components for modern more efficient parts.

These are the original linier voltage regulators. They are the same that was used on the original boards, just more modern design. As you can see there is a heat sink on the 5V regulator. Most of the logic operates on 5V so this part has to deal with a lot more current and therefore get very hot and needs a heat sink to keep it somewhat cool but there is a better option.

Here we have switch mode regulators. These devices do the exact same job as the original regulators but in a much more efficient manner without the heat. A liner regulator supplies a constant voltage and current to devices (known as a load) and this constant current draw generates heat. The replacements are switch mode variants and these switch on and off at a very high speed (known as pulsing) preventing them from heating up. Exactly how they work is way beyond this blog so I just kept it simple.

Once all the power supply components were fitted (and before ANY other component) I applied power so I could run some checks. Although the correct voltages were being generated and measured at the power pins where each microchip would eventually be placed, I noticed that the voltage across one of the capacitors was in excess of 28 volts? This capacitor is a 25 volt part so the voltage measure is out of spec and above the same working limit. I measure this same capacitor on an original board and it measured just over 20 volts which is what i would have expected. I then tested this with a load attached and the excess voltage remained unchanged.

I decided as I could not find any fault, that I would upgrade this capacitor to a 35 volt part to prevent any damage to the component. All other testes were spot on.

As i was using switching regulators I had no use for the heatsink so i moved it to the cassette power transistor which provides power and current to the external tape drive. This part does not generate heat and does not require a heatsink, I just thought It looked cool.

Now for something different….

On the original motherboard the video signal to the TV was produced by modulator, a silver box that was soldered to the board and contained all the RF video circuity. This is not required today and you can use the composite signal to the A/V input on most modern TV today. However, some boards has signal interference or degradation when using composite as noise from the modulator leaked through.

What we have here is a board that replaces the modulator and passes a clean analogue video signal to the output. Its a simple mod created by C0pperdragon and he has made all his projects open source when means I was able to reproduce his design and build these boards myself.

I imported the design into a PCB design tool and checked over it (not that there was going to be an issue) I then sent the design off to a PCB manufacture that i use quite often and once one boards arrived i set about building them up.

As you can see they are all surface mount components and require a magnifying glass so I can see what I’m soldering. I would have used a hot air rework station but I didn't have one at this particular time, I do now and other projects (coming soon) have benefited.

Board completed and fitted where the modulator would have been.