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  • iz8dwf's Avatar
    October 14th, 2017, 12:08 PM
    pettester.bin doesn't check all of the RAM and it doesn't check it very well also. The result you're having are very encouraging, since most of the...
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    October 14th, 2017, 08:46 AM
    piggybacking SRAMs seldom works. However, if you had a garbage screen and you get a completely black screen now, the 2114s are more likely ok....
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    October 14th, 2017, 04:08 AM
    If the ROM doesn't read correctly, it's surely bad, but you might have some oxide on the pins, try gently cleaning all the pins and read the ROM...
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    October 14th, 2017, 12:39 AM
    Good progress: that's the Kernel ROM that actually contains the code to clear the screen, so it's executing correctly (or mostly). That's...
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    October 13th, 2017, 01:49 PM
    The last 2001N that I repaired had the following problems: bad reset circuit 2 x 2114 2 x LS157 1 x 74177 1 x LS373 1 x LS00 <--- after...
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    October 13th, 2017, 12:32 PM
    Just for the record, I've repaired a few (three of them) 2001N boards all showing garbled screen initially and it was never any of the CPU/PIA/VIA. ...
    41 replies | 817 view(s)
  • iz8dwf's Avatar
    September 30th, 2017, 11:15 AM
    In that case, if you always run it on DC, then C39 becomes useless. Frank
    5 replies | 177 view(s)
  • iz8dwf's Avatar
    September 30th, 2017, 09:38 AM
    I assume you've a VIC-20CR, the one that uses a power supply similar to the C-64's one, that provides +5V DC and 9V AC. In this case, C39 smooths...
    5 replies | 177 view(s)
  • iz8dwf's Avatar
    September 24th, 2017, 09:10 AM
    according to the picture posted, that motherboard has a CRTC and 16K of RAM only. Frank IZ8DWF
    9 replies | 295 view(s)
  • iz8dwf's Avatar
    September 24th, 2017, 12:08 AM
    I would suspect the basic ROM, but it really might be a lot of different things. One of the first things I would do in this case is reading all the...
    9 replies | 295 view(s)
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