The Pictorial C64 Fault Guide

Welcome. This web page represents a picture-oriented guide for diagnosing problems with Commodore 64 computers. It's basically an image gallery of various problem scenarios along with their descriptions and known causes.


Keep in mind that the main purpose of this guide is to assist you in diagnosing problems, not to tell with 100% certainty which part is causing a problem. For example, a blank (black) screen upon startup is a common problem, but its causes are so many that it's not even included on this page. Even if your C64 is showing the same symptoms as a listed picture, it's still not 100% certain that the cause is the same - a similar error can often be caused by many different things.


For the best results, use this guide in conjunction with other C64-related sites listed here.


Audio problems are naturally a bit hard to portray with pictures, so I added a separate section for them:

Diagnosing Audio Problems


This web page will always be a work in progress, more pictures will be added with time. If you have a picture to contribute or questions about the currently listed problems/causes, I would like to hear from you:


[email protected]



Click on an image for detailed information about a fault


Normal Startup

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Non-faults

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U1 (CIA)

Common failure!

General tips

U2 (CIA)

Common failure!

General tips

U3 (Basic ROM)

U4 (Kernal ROM)

U5 (Character ROM)

U6 (Color RAM)

U7 (CPU)

U8 (Logic)

General tips

U9 - U12, U21 - U24 (RAM)

Common failure!

General tips

U13 (Logic)

General tips

U14 (Logic)

General tips

U17 (PLA)

Common failure!

General tips

U18 (SID)

See also: troubleshooting audio problems

U19 (VIC)

U25 (Logic)

General tips

U26 (Logic)

General tips

U31 (Oscillator)

General tips

C19 (Capacitor)

CT1 (Trimmer Capacitor)

F1 (Fuse)