The Commodore 64 Fixer
                            by Bill Dun
                 Cincinnati Commodore Computer Club


Code  Check These
  A   6510
  B   6526
  C   6581
  D   8587
  E   PLA
  F   226
  G   227
  H   225
  I   8701


CODES SYMPTOMS

A           Cursor jumps back to the home position
E           Abnormal colors appear in the letters
AD        Different characters are displayed & cursor is locked
ADG     System does not re-set & RESTORE does not work
B          Cursor disappears after warm up
F           SYNTAX ERROR displays after warm up
AG        Systems resets & long programs do not load
BF        Keyboard does not operate when warm
ADFI    Blank screen on power up
A          No cursor displayed, intermittent screen
?          On power up, PRESS PLAY ON TAPE, & display blinks X
A         On power up, the cursor does not work
F         When return is pressed, the cursor goes to home position
F         POKE command does not work
B         Joystick does not operate correctly
BEFH  No character lettering is displayed
BD       Graphic characters instead of letters are displayed
BF        Power up message appears, but no cursor
AB        Device not present when disk is used
B          Disk drive continues to search, trying to load
DE        Incorrect screen colors or no color
B          Keyboard does not work
F          Flashing color or blocks
FG       Game cartridge does not work
E          Unit dead - 40% possibility play
E          User port does not function (ex. modem)
B          No sound
B          Missing notes
BC       Game paddles do not work

White band scrolls down the screen (60HZ hum)      Check p/sup & VR2 reg.
Wavy screen after warm up                                     Check p/sup & 6587
Black band scrolls after warm up                             Check p/sup & VR2 reg.
OUT OF MEMORY error on power up                 Check RAMS 4146-U1-U12,
                                                      U21-U24
Powers up w/graphic display & blinking cursor        Check U14
Powers up with all characters as blocks                   Check U26
Unit completely dead                                               Check power supply
Characters are all over the screen & locks up           Check power supply

PLA CHIP IS AN 8SQ2S100

ROM CHIPS ARE   901226-01 (BASIC)
                901227-01 (KERNAL)
                901225-01 (CHARACTER)