Can anyone help identify these C64 motherboard mods?

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rotanon
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Can anyone help identify these C64 motherboard mods?

Post by rotanon »

Got myself a C64. Apparently the seller said it powered up but I havent tried as yet; waiting for my new PSU to arrive.

Opened it up to check the internals, give it a clean out .... and found two mods that Im curious about. Board is an assy no 250466.
Can anyone help explain these??

Mod 1 - Power switch:
20221024_152147.jpg
Not sure what is going on here. The legs have been cut and then joined with a fuse. I dont think the fuse serves any specific purpose other than providing a conductive bridge. Couldnt find anything on google to help explain this one

Mod 2 - Custom (switchable) Kernal ROM:
20221023_164909.jpg
The unit has (had) a switch on the back of the unit to switch between the different kernel images. The seller said the switch broke off and needed to be replaced. As can be seen in the photo, there is 3 wires coming off the board that currently end at the switch carcuss. Question I have (and the seller couldnt tell me) is how do I wire the switch? Is it a two or 3 position switch ? Is there a specific order the wires need to be connected to the legs of the switch? Tried googling for this specific module, but without any names or markings to help identify, I come up with nothing


levoman
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Re: Can anyone help identify these C64 motherboard mods?

Post by levoman »

In the first picture i think that part of the switch stopped working , so the fuse is there instead of the switch. Replace it with a new switch and you will be ok.

As for the second one , do you have a picture of the switch body? One of the wires will be ground and the other two will be upper address lines . Was the switch single or double pole ( 3 or six connections )?
levoman
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Re: Can anyone help identify these C64 motherboard mods?

Post by levoman »

But it could be that two of the wires are +5v and ground and one address line.
banman
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Re: Can anyone help identify these C64 motherboard mods?

Post by banman »

Hi rotanon and levoman,


That switch looks very sketchy. Have a look at this eBay listing...

https://www.ebay.com.au/itm/New-Commodo ... 56-20017-0

That's the kind of switch you need to look for...The switch is actually a toggle switch which has a plastic rocker mounted to the end of it.

As levoman has suggested the EPROM board will be some type of multi kermal with the ability to switch between different kernals (maybe jiffydos).

I noticed that the EPROM is 27c256. Would that hold 4 X 8kb kernal ROM's
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Re: Can anyone help identify these C64 motherboard mods?

Post by banman »

Is that C64 or C64c mainboard you have, are you able to show a full picture of the mainboard, please?
I see a 1987 dated IC chip in one of your photos......
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