C64 CHIPS and COMMON SYMPTOMS     10-14-97

U1 	906108-02 (6526) VIA 
     Startup screen normal, but no cursor. No keyboard or joyport access. 
Partial failure: some keys or joystick positions don't work. Cartridge
works.

U2 	906108-02 (6526) VIA 
     Startup screen normal. No serial or user port access. "File not
found" error when drive accessed. Cartridge works. Characters sometimes
will show as blocks on startup screen. 

U3 	901226-01 BASIC ROM 
     Blank screen w/ border. Cartridge works. 

U4	901227-03 (early -02) KERNAL ROM	
     Blank screen, no border. Cartridge works.

U5	901225-01 CHARACTER ROM	
     Blank screen w/ border. "Garbage" characters where startup page info
should be.  Cartridge works. 

U7	906107-01 (6510) MPU
     Blank screen, no border. Cartridge doesn't work.

U8	SN7406N LOGIC CHIP
     Drive access problems: drive resets, but "device not present" error.

U9 THRU U12 & U22 THRU U24  	8 RAM CHIPS (4164)
                                2 RAM chips (4464) in C64C
     Blank screen, no border. Shorted chips will get warmer than the other
RAM chips. Partial failure: will sometimes produce garbage screen,
abnormal number of bytes free or "out of memory" error on startup screen.

U17	906114-01 (82S100PLA) PLA
     Blank screen, no border. Sometimes will produce colored screen or
flashing garbage on screen, or cause intermittant screen freeze... 
sometimes after warmup. This chip normally runs hot! Most common chip to
fail.

U18  	906112-01 (6581) SID				
     Normal screen. No sound or garbled sound. Mouse or graphics tablet
pointer stuck or jitters. If shorted, can cause blank or "garbage" screen. 
NOTE: computer will work without a SID plugged in. This chip normally
runs hot!

U19	906109-04 (6567) VIC				
     Blank white screen, no border. Sometimes will produce garbage or
"checkerboard" screen, or screen that lacks contrast. If screen is blank
or garbled from bad VIC, "blind" disk commands from keyboard -may- still
work.

U31	8701 MASTER OSC. (Some C64s use 74LS629N logic chip)		
     Blank white screen, no border. 

POWER PACK: 
     Can produce many problems like blank screen (red LED on or off),
program lock-up, garbage screen, hum bars moving on screen, hum in audio,
damaged RAM chips, intermittant operation after warmup, etc.


Ray Carlsen CET
CARLSEN ELECTRONICS
email: rrcc@u.washington.edu or rcarlsen@i-link-2.net
If you have any questions or comments, please feel free to write,
especially if you spot an error here. Thanks!