NTSC Video Issue After C64R MK2 is Powered On For Extended Time

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  • Five hours of PAL VIC-II 8565R2 later, I feel pretty confident that this PLL instability or whatever is only happening with NTSC VIC-II chips and it does not appear to be related to power supply.

  • Hi

    I'm having the same issue, after about 45 minutes of usage, the image on the screen turns monochrome and after about one and a half hours later, I stop getting feedback all together (screen freezes). I know that the system still runs because I am able to hear sound on my speakers.

    The issue comes up much sooner if I just reset the machine (both on epyx fastload reloaded cartridge and dedicated power switch) after the issue occurred for the first time. I have to wait a longer period of time before the image output is again stable for longer periods of time.

    I have mainly been playing games on the system, it'sva long list with which I'm not going to bother anyone.

    At the moment I have a NTSC VIC-II connected to an active S-Video to VGA converter which is then connected to a VGA LCD.

    I have a PAL VIC-II as well but the image on the LCD flickers when I use it, I suppose it has to do with the 60Hz refresh rate of the LCD and the 50Hz output of the PAL VIC-II. I have not tested if the monochrome image or freeze issues occur with the PAL VIC-II though, the flickering of the screen doesn't make for a enjoyable experience with the machine.

    Further I am using your official power adapter, an original breadbin keyboard and Pixelwizard c64c case, the chips themselves on the board are either new or new old stock, I can provide a list of these if required.

    Finally, I do have a theory about why this issue happens: the chip overheats somehow. That said, it does not happen with the same chip on an original breadbin C64 board. I swapped the VIC-II on that one and ran some demo for more than four hours, no monochrome image, no freeze. I even put the breadbin board in the same Pixelwizard c64c case and ran the test again, same result. This, according to me, means that the C64R-MK2 would be at fault for the aforementioned overheating problem.


    Sorry for the long and explicit message but I thought that a deeper description of the issue and debugging steps taken would serve better to diagnose the problem.


    Thank you and have a nice day,

    Ralph

  • Update

    Since my last (and very long) post, I've installed heatsinks on the VIC-II as well as on the CPU. These are small aluminum units with a height of 5mm. Sadly the issue persists, after about 45 minutes the display image turns monochrome. I've exchanged the display as well, no effect either


    Ralph

  • The voltage appears OK, so the next step would be to measure ripple. Maybe a friend around who has an oscilloscope?


    absolute512 : While temperature is most likely an influencing parameter, it's certainly not the temperature of the VIC-II chip, but something around the PLL on position U23, about "north-east" of the Xilinx chip. My current idea is to move the NTSC operation into a slightly different VCO range. Yet another thing on my long todo-list...

  • While I don't have a C64RMK2 on the dev desk, you could just place your finger on the chip and see if the wiggle goes away.


    I believe it'll be required to either exchange one of the resistors around that chip, or (if I'm lucky) just to add one on top. I need to work that out - I have a rather long list of stuff that I need to look into, and I had almost no time to work on any developments during the past five weeks. This will change now, as my other business doesn't require that much attention any more.

  • The voltage appears OK, so the next step would be to measure ripple. Maybe a friend around who has an oscilloscope?

    I asked a friend with an oscilloscope and he basically told me he does not do unpaid development work for other people's projects.


    Jens , are you suggesting that the ripple from the power supply is causing this behavior? Because there are a number of people in this thread including most recently @absolute512 using the official power supply and reporting the same kind of problems with NTSC VIC-II chips.

  • A quick ripple measurement on the supply voltage is not exactly "development work". The person could have just said "no". Give me a few days until I have finished work on Indivision ECS V2, then I'll turn to this NTSC issue, again (yes, I've tried to reproduce it twice already, failed, but I'll give it another try).

  • A quick ripple measurement on the supply voltage is not exactly "development work". The person could have just said "no". Give me a few days until I have finished work on Indivision ECS V2, then I'll turn to this NTSC issue, again (yes, I've tried to reproduce it twice already, failed, but I'll give it another try).

    Hi Jens , I'm only repeating what he said to me. I ordered your official power supply just now, however. So we can see if that makes a difference. Looking forward to seeing what you determine. Thanks!