To the original author:
I’m just preserving your valuable information. Just in case it would ever go offline.
As always I would like to refer to the ORIGINAL source.
BTW: I’m using the most interesting and common errors, because some aren’t c64 related, but user errors. 🙂
Description
Whenever grey raster (or anything with rapidly alternating pixels) is drawn, the grey color instead appears as bars or red and green. This is not due to a fault in the C64 itself. It happens when composite video or RF is used and the high frequency pattern is misrepresented as color information. Using S-Video should fix or lessen this problem, as it keeps the brightness and color components separate.
Cause
Color bleeding of Composite/RF
Description
In some parts of Giana Sisters, graphical errors blink for a fraction of a second. This is just a bug in the software, and can even be reproduced with emulators. In fact, 99% of the time when you see simple graphics anomalities like this in games, it is simply caused by unpolished software. So before suspecting your C64 hardware, make sure it’s not actually normal behavior for the game/program in question. NOTE: the video is slowed down to make it easier to see the errors.
Cause
Unpolished software
Description
Computer operated normally, except video output was glitched, as if it were out of sync. Both RF and Composite displayed the same problem. Swapping in another VIC chip and re-capping did not fix it either. It turned out to be a compatibility problem with the LCD TV. The television worked fine in other use, but would not work properly with a C64. NOTE: ‘Device not present error’ not related to this problem.
Image(s) by novoiperkele @ com64.net
Cause
Incompatibility between C64 and LCD TV
Description
Fuzzy colors on video output. This happens if you connect a C64 to a TV with an S-Video cable, but the TV either doesn’t support it, or has it switched off. The fuzzy colors are caused by luminance/chrominance leakage.
Cause
Using S-video cable with a TV that doesn’t support S-video, or S-video mode not switched on
Also; it’s best to use an original Commodore 1701 or 1702 monitor. It has Luma and Chroma inputs. it would be best to use a L/C/A cable.
Description
image 1:
Relatively normal startup screen, but frozen with a rapidly flashing cursor and ‘LOAD’ command run automatically. No response to keyboard commands. A cartridge game loaded up properly but joystick and keyboard did not work. Picture re-created with VICE C64 Emulator.
Image(s) by Ozsoft @ lemon64.com
images 2,3,4:
Caused various abnormal startup screens, including a simple black screen on a couple of boots. The most common outcome was an empty blue screen with borders (first picture). After about 10 seconds of waiting, most of the normal startup text appeared along with some garbage characters, and in some cases automatically typed load/run commands (second picture). Sometimes the characters kept switching between upper and lower case. On one boot, screen was filled with white garbage characters (third picture). The computer seemed unresponsive on every boot.
Though in this case the problems were simply caused by a bad connection between the CIA1 chip and its socket, similar symptoms can likely be caused by a failing CIA chip.
Cause
– Bad U1 (CIA)
– Bad socket contact on U1 (CIA) – bottom pin(s)
Description
Normal borders, but garbage in the middle. Sometimes after a while or when you try to load something from disk (the drive won’t start to load).
Cause
– Bad U2 (CIA)
Description
Startup screen with normal blue colors and borders, but content area completely empty. A cartridge game worked normally. It turned out to be a faulty Basic ROM chip. A blank blue screen like this is the most common symptom of a bad Basic ROM. Cartridges bypass the Basic ROM so they are good for diagnosing problems with that chip.
Image(s) by danko @ lemon64.com
Cause
– Bad U3 (Basic ROM)
Normally booted to a black screen. With Jupiter Lander game cartridge inserted, produced the garbage screen shown above. Removing the Kernal ROM allowed Jupiter Lander to boot normally, and replacing that chip resolved the issue. Note that Jupiter Lander bypasses the Kernal ROM and is usually not affected by a fault in that chip. But as this fault proves, it’s still possible.
Image(s) by mrr19121970 @ lemon64.com
Bad U4 (Kernal ROM)
Description
Normal operation of the commodore 64, everything works, but you’ll see artifacts in characters like
– stripes through characters
– random moving / changing characters
Image(s) by craftsman1234 @ lemon64.com
Cause
Bad U5 (Character ROM) or bad connection to the ROM
Description
Startup screen with some missing characters. Certain columns are missing. Games also had missing characters. The computer was mostly functional, commands worked normally. Diagnostic Cart Rev 586220 froze when it reached the Color RAM test. Swapping in a new Color RAM chip fixed the problems. Image(s) by jts-78 @ com64.net
other screenshot
Startup screen was normal and the computer was operational, but changing the cursor color to white revealed a problem: another character also turned white. Which character was drawn white depended on the position of the cursor. In addition, games had abnormal graphics. Replacing the Color RAM fixed the symptoms. Image(s) by lolhead @ lemon64.com
3rd screenshot
System worked fine except that colors were incorrectly displayed. Problem went away after U6 color ram was replaced. Image(s) by zxspectrum_16k @ lemon64.com
Cause
Bad U6 (Color RAM)
Description
Garbage, hanging system, problems with larger programs.
Cause
Bad U7 (CPU)
Credits
Image(s) by Fastah @ lemon64.com
Image(s) by jts-78 @ com64.net
Image(s) by josephdewes @ lemon64.com
Description
Startup screen filled with vertical bars & blank space. NOTE: weird colors due to display/camera, not related to this problem.
2nd:
Machine was working normally, except that it hung when trying to load via a disk drive. There was no reaction from the drive. The screenshot depicts the point where it hung. Swapping the CIA chips U1 and U2 did not make a difference. Replacing the 7406 logic chip at U8 finally resolved the problem.
Cause
Bad U8 (Logic)
Credits
Image(s) by thasti @ forum64.de
Description
Startup screen problems with: memory error, wrong number of memory available, colored random characters.
Cause
Bad RAM chips or bad socket contacts of the RAM
Please see description of the images for the cause
Description
A startup screen full of random characters or strange images, similar to one caused by bad RAM. In most cases the C64 still works. Also in many cases the C64 works with a (deadtest) cartridge.
Cause
Bad Logic Chip U13
Description
A startup screen with incorrect characters, you’ll see most of the time that there’s incorrect placement of text. In all cases the Commodore does function correct, but incorrect display of characters.
Cause
Bad Logic Chip U14
Description
A start up screen with demo scene like problems like colored characters, flashing colors, stripes etc. looks like a Bad PLA U17 chip.
Cause
Bad PLA Chip U17
Description
A defective SID can (next to no sound or digi) produce a black screen. You can debug to remove the SID and turn the C64 on.
Never ever interchange a 6581 with a 8580, it can kill your C64!
Cause
Bad SID Chip U18
Description
A defective VIC presents all kinds of video problems. For example black vertical stripes, strange colors, a shadow etc.
Cause
Bad VIC Chip U19
Description
Initially had a black screen on startup, which was fixed by a PLA swap. After that, random black/blue characters (shown above) displayed on startup. Dead test cartridge worked and the memory test completed successfully. Swapping in new RAM, U13 and PLA did not cure this symptom. Replacing U25 finally did the trick and the machine booted up normally. The failed U25 was a MOS version of the chip, which are known to fail more often than their non-MOS counterparts.
Cause
Bad Logic Chip U25
Description
Seeing distortion smaller than the size of characters, then it could be the Logic Chip U26
Cause
Bad Logic Chip U26
Description
Typical out-of-sync video problems? Then it’s the oscillator.
Cause
Bad U31 (Oscillator)
