The Pictorial C64 Fault Guide

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.


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:


derbiangames@gmail.com


Best of luck in bringing these legendary old computers back to life!


Click on an image for fault details.

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)

General tips

U4 (Kernal ROM)

General tips

U5 (Character ROM)

General tips

U6 (Color RAM)

U7 (MPU)

General tips

U8 (Logic)

General tips

U9 - U12, U21 - U24 (RAM)

Common failure!

General tips

U13 (Logic)

General tips

U14 (Logic)

General tips

U16 (CMOS quad bilateral switch)

U17 (PLA)

Common failure!

General tips

U18 (SID)

See also: diagnosing audio problems

U19 (VIC)

General tips

U25 (Logic)

General tips

U26 (Logic)

General tips

U27 (Logic)

General tips

U31 (Oscillator)

General tips

CT1 (Trimmer Capacitor)

F1 (Fuse)

Capacitor

Trace

Power supply

General tips