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Commodore 64 System Saver


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Some may already know that Commodore 64 power supplies can cause major damage to the computer when something goes wrong with them. When the regulation circuit fails it can allow 9v through to the 5v rails in the computer causing a lot of damage.

This unit is based on a circuit designed by Ray Carlsen who has been building system savers and replacement power supplies for a while now. It will cut the power to the computer when it gets above 5.4v.

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Due to the cost of the units from America and postage costs Ray's units can be quite expensive so I decided to build my own.

I designed a board to suit this circuit that also has a 7pin Din socket and a 300mm cable with a 7pin Din plug. The idea is to just plug your psu into this unit and plug the unit into the computer, Simples.

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There are two LEDs on board, Red for a fault indication and Green for OK status.

I originally designed the board to be wrapped in clear heatshrink tubing (BYO) but I've also designed a 3d printed case that requires wires to be run from the LEDs to the board.

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Once all the parts arrive I'll be making a few for sale with or without cases so watch the sales posts for pricing.

Cheers Trev

 

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Expressing interest in 1 x cased unit.

 

PCB looks great! Are you sure the power traces are thick enough though? Seems they could be beefed up a little, at least 50mil.

 

Hi Frank. Power traces are .6mm any bigger and the gnd fouls with the 5v and 9v on the connector. I'll test it thoroughly before I sell any.

Test unit waiting for transistors and socket.

Cheers Trev6069ff9bf082f2fe94955b5f05bffc4c.jpg

 

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One slight mod and it works fine. I picked up the wrong pin on the connector for Gnd. The diagram was just a little ambiguous so I checked the pins on my psu.

The test unit turns off at 5.75v and back on at 5.74v off load, so it wasn't plugged in to the C64. I'll give it another test under load for an hour or two just to be sure.

5.74v is way below the maximum limits for the 6510 and the TTL chips which is 7v for a short period according to the data sheets.

I'll do a bit more testing on the C64 today and if all is well I'll assemble a batch on the weekend and print a few cases.

Cheers Trev.

926716c70291e105c2f72970274f2e17.jpg677a7e81a06bd251a56269912ddca0b9.jpg

 

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You know what would be a cool addition? One of those mini voltmeters. I have a few here as I plan on incorporating them into my supergun, once I receive one of your power savers I'm going to add one to it. Should be easy to mount to the printed case.
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You know what would be a cool addition? One of those mini voltmeters. I have a few here as I plan on incorporating them into my supergun, once I receive one of your power savers I'm going to add one to it. Should be easy to mount to the printed case.
Maybe in V1.2[emoji16]

 

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One of those is mine!

 

Case looks brilliant, think you may have given me the 3D printing bug. Something I need to invest in, just a bit time poor at the moment.

 

How does the PCB mount to the case? Is there strain relief for the cable?

 

I've not seen a PCB with a different solder mask on each layer, is that an option from the PCB manufacturer?

 

Sorry for all the questions!

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One of those is mine!

 

Case looks brilliant, think you may have given me the 3D printing bug. Something I need to invest in, just a bit time poor at the moment.

 

How does the PCB mount to the case? Is there strain relief for the cable?

 

I've not seen a PCB with a different solder mask on each layer, is that an option from the PCB manufacturer?

 

Sorry for all the questions!

 

There's no mounts for the pcb it's a snug fit and the socket and lid hold it in place.

There is a small loop of cable inside the case and I'll put a cable tie around it just inside.

I thought that because it's a single sided board I didn't need a mask on top. If I do more I'll fix that. I only supplied a gerber file for a copper side solder mask so that's all they did.

I need to modify the lid as it's not sitting flat over the socket and I also need to make the cable entry hole just a tad bigger.

Cheers Trev059066e94d2bf6a0a9d9b2b3f20f3ead.jpg

 

Sent from my SM-G930F using Tapatalk

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