I recently purchased a C64 off of Goodwill. It was cheap, but they were unable to test anything other than to see if it turned on. I made my own AV cable by splicing a MIDI and an RCA cable. Picture works fine, but the sound isn't working properly. When trying some of the sound demos in the manual as well as some simple sound tests I made myself, I can hear the sound of the background noise changing, but there is no obvious sound. I'm not sure if the problem is with the SID, or if it is with something else? Any ideas on what is wrong?

It's highly likely that there's an issue with the SID chip. From what I've heard they're super sensitive and can easily be burnt out, so I guess the solution would be to grab one off ebay and chuck it in and see if it works. Alternatively it could just be a solder joint issue somewhere down the chain, so best to open it up and have a look at the board. If the board looks clean then it's likely a SID issue.

Yeah I opened it up and it looks fine. Geh. SID Chips are so expensive. Buying a new one costs just as much as my commodore. I'll probably just hunt some thrift stores again for a new C64...

It could also be a problem with the power supply: there are two different currents provided by a c64 psu, one for the C64 (5V DC), and one for... the SID chip (9V AC).

You can try to get a SwinSid replacement, I found one on ebay for a price lower than a real SID (I can't find any now on ebay though). It seems the swinsid doesn't rely on the 9V AC current and can be powered with the 5V dc part.

There is also the swinsid ultimate which sounds really cool, and is around the price of a normal SID: https://www.facebook.com/swinsidultimate/

Last edited by garvalf (Nov 7, 2016 7:06 am)

Ah yes. I opened up the power supply to test it and it was full of this solid grey goo that smelled like chemicals and completely denied me access to the circuits inside(I'm not sure if that's normal, but the power supply may have borked the SID. I'll check for continuity). Thanks for the advice. If I don't find a C64 for cheaper, I'll go ahead and grab a SwinSID Ultimate.

UPDATE: *sigh* okay...my power supply is even more messed up than I thought...It only has 4 pins, and they're wired VERY strangely. I'm unable to test the voltage, but it's not looking good. I'll most likely post a video in the future detailing the weirdness, but for now I think I'll just get a new commodore and sell the old one to a friend or something.

Last edited by Kuesa (Nov 8, 2016 4:15 am)

The 4 pins are normal and the grey epoxy is normal too. Not ideal, but normal.

Welcome to the club!

If you go for another SID be careful which revision you pick. 6581 and 8580 are NOT compatible in the meaning of voltage, 6581 requires 12V, 8580 needs only 9V. Check the original SID and the PCB Assy number. This page can help you to identify the stuff: https://ilesj.wordpress.com/2010/07/01/ … sid-model/

The SwinSID (either the old or the Ultimate) is a good and relatively cheap replacement, you don't need to worry about voltage differences and can put it into any PCB.

It's very rare you'd come across one but adding to what str was saying: Despite starting with the same 3 numbers as the 6581, the 6582 is actually the same voltage as the 8580. Same fixed filter and fixed wave mixing dye is inside that chip as the 8580.