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64 TROUBLESHOOTING GUIDE (Continued)

SYMPTOM
POSSIBLE SOLUTION
Cursor jumps to back to home position. Check U7 (6510 MPU)
Abnormal colors appear in the letters. Check U6 (2114 RAM)
U16 (4066 IC)
Different characters are displayed and cursor is locked when turned on and off. Check RAM
System does not reset and the 'RESTORE' key does not work. Check U20 (556 IC)
White band scrolls down the screen. (60 HZ HUM) Check External Power Supply
VR2 (5V Regulator)
Cursor disappears after the system warms up. Check U1 (6526 CIA)
SYNTAX ERROR displayed after system warms up. Check RAM, U3 (ROM)
Wavy screen after the system warms up. Check External power supply
U31 (74LS629 IC)
U30 (74LS193 IC)
The system resets when it warms up. Check U7 (6510 MPU)
U3 (ROM)
Keyboard does not operate correctly when the system warms up. Check U1 (6526 CIA)
U3 (ROM)
Black band scrolls through screen when the system warms up. Check External Power Supply
C90, C88, CR4
VR2 (5V Regulator)
Cassette motor keeps running. Check U7 (6510 MPU)
Cassette motor keeps running even after a program is done loading. The TIP 29 transistor gets extremely hot and the fuse may possibly blow. Check Cassette Port for Shorts
R4 (Possibly Open)
The cursor disappears when the cassette is plugged in. Check U7 (6510 MPU)
Cassette runs extremely slow. The program seems to load but will not run. Check U7 (6510 MPU)

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This page has been created by Sami Rautiainen.
Last updated February 11, 1998.
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