C64 Audio Issues

C64 No Audio

Picked up a totally sweet SD2IEC board which allows emulation of the Commodore floppy drive from a SD card. It’s similar to the SIO2SD boards that do a similar function for the Atari family of home computers, except for C64. After getting it hooked up and being fairly impressed with the unit I noticed that my C64 doesn’t have sound. The one thing the machine is known for — it’s missing.

First step was checking power supplies. Oddly I had a 2nd PSU on hand, swapped it in place and no go. The internet said it could be a culprit, this makes sense as the power supply has a DC line which would be used by the logic chips that make up the computer as well as an AC line which is commonly used for opamp ICs and stuff that has a +/- power feed. Anyhow the power supply checked out A-OK which doesn’t solve issue.

Next step was to open the thing up, and hunt. Looking online I found details where the SID chip was and the datasheet. Poking at the chip while a music disk / demo was playing I could see the address and data lines were busy so not decode logic or data bus buffers to the naked eye. The thing is the output side of the chip just sits at a high voltage so it seems toasted. I didn’t check the two external capacitors, maybe later. The thing is the SID chip is the value of the machine and places like eBay are full of fake copies from China that don’t function. So this one goes on the shelf until a parts machine turns up.

UPDATE 5/3/2917

Matt Crainer brought me a donor C64 that had already been robbed of it’s keyboard controller IC. I carefully de-soldered the SID chip. I didn’t have a 28 pin DIP socket on hand, and instead of ordering one I ordered some break-away SIP sockets. The quality of the machine pin holes was not up to that of what I would get from a mainstream commercial mail order house machined DIP sockets, but it was good enough. Soldered two 14 position sip sockets. I cleaned up the SID chip first, trying to remove any excess solder or burs on the pins, didn’t want them to bend on insertion. Threw it in. Powered on the C64. I googled for some hints as to how to get sound without digging out the SD drive emulator and found a post from VCF/MARCH forum I believe on some addresses to poke. Noise was heard! All is good. Buttoned it all up and this project is checked off!!!!

Picture added to slides above of soldered in SIP socket.

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