LARRY'S COMMODORE 8-BIT PROBLEM TROUBLESHOOTING LIST

Updated 02/14/1999 BY LARRY ANDERSSON, COMMODORE COLLECTOR AND ENTHUSIAST

This is a simple checklist FAQ of some of the easily correctible but not always well known problems you may experience with your Commodore 8-bit computer.

NOTE: This FAQ is by no means complete, much of the information covered here deals with Commodore 8-Bits that I have had experience with and reference materials on. If you have stuff to add or revisions to current information please e-mail me at:

larry@portcommodore.com

• (64) If the screen is full of multi-colored garbage text, it is most likely that your power supply died.
• PET If you get a Blank Screen you might have your IEEE-488 connector in the user port by mistake or your user port device cable upside-down.
• Some 'flat' 128's power switches can't fully engage because of the case design, if you get 'flickering' try filing the hole around the switch.
• PETs are prone to have the chips come unseated from their sockets. With the computer OFF, Push down (not too hard) on the top of each socketed chip, turn back on the power and see if it made a difference.

• Make sure the 'shift-lock' key is not locked down
• Check the joysticks that are plugged in, if one is pushed to the side or the fire button is jammed down, this will cause keyboard problems.
• Check the keyboard for stuck-down keys (this happens from time to time, especially on SX 64s.
• On older machines the keyboards may become dirty were some keys cease working. (This text presently does not have a keyboard cleaning procedure, but I will write one in the future.

• TVs and Monitors put out alot of interference - especially on the left side of the screen, Datasette Drives or Disk Drives may not communicate well if they are too close to the display or on the left side, try re-arranging your drives so they are to the right of your monitor with some space not to the left or too close to it.
• Some commercial programs leave the floppy drive's read/write head on a half-track and make the drive unable to read disks. Try sending an Initialize Drive command (below) without a disk in the drive to reset the heads, then try loading again.

OPEN 15,8,15,"I":CLOSE 15

• If it is a drive you just got it may not be set for device 8, try loading the directory using device 9, 10 or 11. (i.e. LOAD“$”,9)
• The 8050, 8250, and SFD-1001 cannot read disks created with the 1541, 1571, 4040 or 2031. Make sure you are using a comaptible disk formats.
• On the PET using tape, make sure sound is turned off: POKE 59464,0:POKE 59466,0:POKE 59467,0 The sound generator interferes with the tape operation.
• Add a 0: (or 1: for second drive) before the file name of disk programs, this will make the disk attempt an Initialize before loading the file.
• If you are trying a LOAD“*”,8 try doing a LOAD“?*”,8 It sometimes does the trick. Also see previous hint.
• If you are using a fast-loader cartridge or ROM, it may not be comaptible with the drive or program you are trying to use.

• (Tape) make sure the 'write protect tab' isn't punched out, if it is, you will need to cover the write protect hole with tape.
• On the PET tape make sure sound is turned off: POKE 59464,0:POKE 59466,0:POKE 59467,0 The sound generator interferes with the tape operation.
• The Commodore 2040,4040,2031,8050,8250,SFD-1001,1540,1541,1570,1571, and 1581 cannot reliably use high-density disks. Use Single or Double Density Disks on the 2040,4040,2031,1540,1541,1570,1571, and 1581. The 8050, 8250 and SFD-1001 use 96 track per inch Disks. Use them if you can find them, though you can use Double Density disks without problem.
• If it is a previously used disk that is giving you heck, make sure to add the 2-character disk id (i.e. “N0:NAME,ID”) to do a complete disk format and not a simple directory erase.
• Add a 0: (or 1: for second drive) before the file name of disk programs, this will make the disk attempt an Initialize before saving the file.
• Are you using a unique file name? the Disk Drive will not automatically overwrite old files. Issue a 'scratch file' command before saving.
• Beware of old commercial software disks, some nasty (and stupid) vendors punched holes (which can mess up the drives heads) in the recording area.
• 1581 diskettes are VERY prone to failure (called the click of death, as the disk starts making a clicking sound when unreadable), handle with care.

• Over the years Commodore changed the Commodore 64's method of how it assigned color to the characters on the screen (which are blank) when it clears it. Some programmers assumed cleared screens will contain white characters or the last used character color, which is not always the case.
  Fortunately there are not too many programs with this problem.

• Commodore's CP/M cartridge for the 64 relies on precise timing of the 64 when Commodore did revisions to later 64s that timing was altered. Only early model 64s have the compatible timing to support the CP/M cartridge.
  A good sign you have an early 64 is if the video connector has ony 5 pins instead of the 8 in the later 64s.