Video comes up fine then after a bit scrambles itself requiring a reboot

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Don't Panic. Please wash hands.
  • I have my MKII setup and running great but recently the video randomly scrambles itself - requiring a reboot - My thoughts were that the VIC II chip is funky. I have tried a diagnostic cartridge but it constantly reports that tape and other interface chips are bad even though they are obviously not. Does anyone have any suggestions to investigate? I have a Sony PVM monitor that will do PAL and NTSC so I ordered a new PAL Vic II chip to try.

  • This may be a simple contact problem - please try to shift the VIC chip sideways with the socket closed (lever down). This will scratch the contacts and make good contact in case the pins are oxidized.


    What type of power supply are you using?

  • This may be a simple contact problem - please try to shift the VIC chip sideways with the socket closed (lever down). This will scratch the contacts and make good contact in case the pins are oxidized.


    What type of power supply are you using?

    the one supplied by icomp. I captured some pictures. the clear one is at startup and the other is at some random interval while running


  • This may be a simple contact problem - please try to shift the VIC chip sideways with the socket closed (lever down). This will scratch the contacts and make good contact in case the pins are oxidized.


    What type of power supply are you using?

    I also pulled the chip and cleaned off all the contacts with deoxit and reseated it -same

  • And this is a PAL VIC, or an NTSC VIC chip?


    If it's NTSC, you may experience the same (rare) PLL drift that I already tackled, but never got feedback on the fix, which is why it didn't make it into the main deliveries.

  • And this is a PAL VIC, or an NTSC VIC chip?


    If it's NTSC, you may experience the same (rare) PLL drift that I already tackled, but never got feedback on the fix, which is why it didn't make it into the main deliveries.

    currently its NTSC but I ordered a new old stock PAL VIC II Chip as my SONY PVM will do NTSC, PAL, and Secam

  • on a side note the Sony PVM I have, in my opinion, is one of the best retro monitors available.

    2 Composite

    1 s-video

    analog RGB and

    digital RGB


    I have my TS1500 is hooked up to it through an RF demodulator to one of the composite ports


    This is also ideal for a commodore 128 as you can view both s-video in commodore 64 mode and 80 columns -in 128 mode hooked up to the digital RGB port

  • I have been running a graphics loop basic program on the TS1500 just to make sure it is not the monitor - so far it does appear to be a fault with the Commodore, but that said my current bet is that the VIC II chip is funky or the Drift discussed earlier with NTSC

  • Please see this posting with my siggestion of adding a 100k resistor in parallel to R32, carefully lowering it's total value. Reading that thread today looks like a more sophisticated mod may be good, one that steps up the center frequency of the PLL only if NTSC is detected.

  • Please see this posting with my siggestion of adding a 100k resistor in parallel to R32, carefully lowering it's total value. Reading that thread today looks like a more sophisticated mod may be good, one that steps up the center frequency of the PLL only if NTSC is detected.

    i looked at that thread and the video the one person posted is exactly what I see. I am a diaster at soldering so ill wait for the PAL vicII and see if that works