The definitive pictorial diagnostic guide for Commodore 64 computers.
This guide lists pictures of various Commodore 64 problem scenarios along with their descriptions and known causes. Use it as a tool to assist in diagnosing C64 issues, to get a general idea of what might be wrong with your machine. Keep in mind that it's rare to find an exact match and sometimes multiple different problems can cause a similar faulty screen. This site focuses on the classic breadbin models, though many of the fault scenarios are also applicable to newer revisions such as the C64C. For the best results, use this guide in conjunction with the other C64-related sites listed here.
Even if the guide can't pinpoint the exact failing component for you, it may be able to point you toward the general area of the fault on the mainboard. Getting a RAM-like symptom but all memory chips tested working? Maybe there is a broken trace or solder joint near the RAM chips.
Since audio problems are difficult to portray with pictures, here is a separate section for them.
The site will always be a work in progress, more pictures will be added as they become available. If you have a picture to contribute or questions about the currently listed problems/causes, feel free to contact me:
Best of luck in bringing these legendary old computers back to life!