====== The Commodore 64 Fixer ======

by Bill Dun, Cincinnati Commodore Computer Club 

**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

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

^  CHECK THESE  ^^^^^^^^^  SYMPTOMS  | 
^6510^6526^6581^8587^PLA^226^227^225^8701|-|
^  A  |     |     |     |     |     |     |     |     |Cursor jumps back to the home position|
|     |     |     |     ^  E  |     |     |     |     |Abnormal colors appear in the letters|
^  A  |     |     ^  D  |     |     |     |     |     |Different characters are displayed & cursor is locked|
^  A  |     |     ^  D  |     |     ^  G  |     |     |System does not re-set & RESTORE does not work|
|     ^  B  |     |     |     |     |     |     |     |Cursor disappears after warm up|
|     |     |     |     |     ^  F  |     |     |     |SYNTAX ERROR displays after warm up|
^  A  |     |     |     |     |     ^  G  |     |     |Systems resets & long programs do not load|
|     ^  B  |     |     |     ^  F  |     |     |     |Keyboard does not operate when warm|
^  A  |     |     ^  D  |     ^  F  |     |     ^  I  |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|
|     ^  B  |     |     ^  E  ^  F  |     ^  H  |     |No character lettering is displayed|
|     ^  B  |     ^  D  |     |     |     |     |     |Graphic characters instead of letters are displayed|
|     ^  B  |     |     |     ^  F  |     |     |     |Power up message appears, but no cursor|
^  A  ^  B  |     |     |     |     |     |     |     |Device not present when disk is used|
|     ^  B  |     |     |     |     |     |     |     |Disk drive continues to search, trying to load|
|     |     |     ^  D  ^  E  |     |     |     |     |Incorrect screen colors or no color|
|     ^  B  |     |     |     |     |     |     |     |Keyboard does not work|
|     |     |     |     |     ^  F  |     |     |     |Flashing color or blocks|
|     |     |     |     |     ^  F  ^  G  |     |     |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|
|     ^  B  ^  C  |     |     |     |     |     |     |Game paddles do not work| 

^  SYMPTOM  ^  CHECK THESE  ^
|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)