*** Note *** this information is presented without warantee or gaurantee
to it's reliability or effectiveness.  Nor does it imply that these
methods will work or are the only ones possible.

Reprinted from the Commodore Club of Rockford Newsletter - March 1993


                      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)