Mögliche Urschen eines defekten Startbildes

    • HOL2001
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    • Mögliche Urschen eines defekten Startbildes

      latest additions and corrections: 1-31-06

      U1 906108-02 (6526) CIA
      Startup screen normal, but no cursor. No keyboard or control port
      access. Partial failure: some keys or joystick positions don't work, one
      character appears ahead of startup cursor, screen fills at startup as if
      keys are being held down. Cartridge works.

      U2 906108-02 (6526) CIA
      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
      Normal startup border, but "garbage" characters where startup page
      characters should be. Cartridge works.

      U6 2114 SRAM (COLOR RAM)
      Startup screen shows flickering characters with shimmering colors.
      check also PLA U17.

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

      U8 7406 LOGIC CHIP
      Blank screen. Partial failure: drive access problems: drive
      resets, but "device not present" error.

      U9 THRU U12 & U22 THRU U24 8 RAM CHIPS (4164)
      note: only 2 4464 RAM chips 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.

      U13 74LS257 (or MOS7708 ) LOGIC
      Blank screen or less than 38911 bytes free at startup.

      U14 74LS258 LOGIC
      Blank screen.

      U15 74LS139 LOGIC
      Blank screen

      U16 CD4066 (generic CMOS quad bilateral switch)
      Color problems such as random color "checkerboard" pattern on screen
      or no color.

      U17 906114-01 (82S100PLA) PLA
      Blank screen, no border. It can produce colored screen or flashing
      color garbage instead of startup screen. It can cause intermittant loss of
      cursor, screen freeze and/or program crashes after warmup and it can put
      random characters on screen. This chip normally runs hot. It is the most
      common chip to fail in the C64 and it should run no hotter than the SID.

      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 (unplug to check). This
      chip normally runs hot.

      U19 906109-04 (6567) VIC (PAL version is 6569)
      Blank screen (may be light or dark) with 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.

      U20 556 LOGIC, TIMER
      Blank screen. Computer will not reset, or RESTORE doesn't work.

      U25 74LS257 (or MOS7708 ) LOGIC
      Blank screen or less than 38911 bytes at startup.

      U26 74LS373 LOGIC
      Startup screen has normal border, but characters are scrambled.

      U27 74LS08 (or MOS7712) LOGIC
      Normal startup border, but screen full of "garbage" characters.

      U28 CD4066 (generic CMOS quad bilateral switch)
      Normal startup screen. Proportional mouse or graphics tablet
      doesn't work in one or both control (joystick) ports.

      U29 74LS74 LOGIC, DIVIDER
      Startup screen shows normal characters in multicolored "rainbow".

      U31 8701 MASTER OSC. (Some C64s use 74LS629N w/ support logic)
      Blank white screen, no border. Normal "whine" in nearby AM radio
      will be missing if the oscillator is not running. Check also VIC U19

      U32 4044 CMOS LOGIC
      No monitor picture, just diagonal lines on screen.

      Can produce many problems like blank screen (red LED on, dim, 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
      Quelle: personalpages.tds.net/~rcarlsen/cbm/C64-IC.txt

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