6526 and 6526A CIA Chip Information
Possible causes for game port, keyboard, user port, serial port and cassette port malfunction on the Commodore 64 and 128

The 6526 or 6526A CIA chip is the most commonly needed replacement chip for the Commodore 64 and 128. If you can't get any joystick to function properly on your Commodore 64 or 128 or if a certain pattern of keys (like every other key or a diagonal row of keys) doesn't seem to work or if the cursor just marches across the screen without any key being pressed then you probably need to replace the 6526 CIA chip (marked U1 on most Commodore 64 boards). Usually this chip gets blown out by accidently touching one of the pins on the joystick port when you have static electricity on your body (from walking across a carpet or from touching the TV or monitor screen). This is also the same chip as the U2 chip (on most Commodore 64 boards) which may need to be replaced if the cassette drive, the user port and/or the serial port are having problems. Note: If the chip is not in a socket then you will need to get someone who knows how to desolder chips to remove it for you and install a 40 pin chip socket (available below). Important: Once you replace the chip make sure to keep static electricity away from the joystick ports of the computer or you might end up Zapping it again!

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