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Thread: C= Pet 'Abraxus' found in Australia?

  1. #21
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    Quote Originally Posted by TRS-Ian View Post
    The only other Eproms I can see are UD11 and UD12 marked L/C and F. Maybe character generator roms?

    Ian.
    Those eproms are in the option ROM sockets ($9000 and $A000). I see "V/C" not "L/C" and it could be VisiCalc. That red box looks like it plugs into the cassette port. It might be a dongle for Visicalc. Not sure what the other "F" eprom is. Can you dump both just incase?

    Steve
    WANTED: CBM-II hardware or software, PET software

  2. #22
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    Done.

    F: http://ianmav.customer.netspace.net.au/downloads/F.bin

    VC: http://ianmav.customer.netspace.net.au/downloads/VC.BIN


    They are both burned onto 2532 chips but I'm thinking there is just two copies of the program on each Eprom. F appears to stand for Freind.

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  3. #23
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    Quote Originally Posted by TRS-Ian View Post
    Done.

    F: http://ianmav.customer.netspace.net.au/downloads/F.bin

    VC: http://ianmav.customer.netspace.net.au/downloads/VC.BIN


    They are both burned onto 2532 chips but I'm thinking there is just two copies of the program on each Eprom. F appears to stand for Freind.

    Ian.
    Thanks again. I've never heard of the "Friend Wordprocessor".
    Confirmed VC.BIN is VisiCalc, although it appears to be different than the version I have archived.

    Steve
    WANTED: CBM-II hardware or software, PET software

  4. #24
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    The V/C chip seems to be suffering some byte rot. It took several goes to read it by my eprom programmer, with varying checksums. The one attached seemed to be the most consistent when comparing the file buffer with the chip. By contrast the F chip read in perfectly first time and had a consistent checksum.

    Can someone point me in the direction of a troubleshooting guide to start on this 8096. It appears completely dead, it might be something as simple as needing a new transformer or e-cap, ... just need to know where to start looking.

    Cheers,

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  5. #25
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    Quote Originally Posted by TRS-Ian View Post
    ...Can someone point me in the direction of a troubleshooting guide to start on this 8096. It appears completely dead, it might be something as simple as needing a new transformer or e-cap, ... just need to know where to start looking.
    That's actually the least likely cause but it's still a good idea to check the main voltages; you'll find all 3 at any of the 416 type RAM chips along the heat sink:
    Pin 1: -5V
    Pin 8: +12V
    Pin 9: +5V
    Pin 16: Ground reference.

    For future reference what is the main board version number (along the right edge)?

    m

  6. #26

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    If you havenít already done so, I would also gently remove the 64k board from the machine, then remove the 6502 processor from that board and put it back in place on the main motherboard.

    This should make it more of a standard model though with custom Roms. This removes one variable from the list.

    The Zimmers.net website has lots of info on the commodore pet including schematics which may help.

    Andy

  7. #27
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    The main motherboard is a 8032080 and the 64K board is a 8032110.

    I've checked the fuse and it's OK, but the computer shows absolutely no signs of life which is why I plan to start with the voltages.

    On a TRS-80 like this I can turn up the contrast and brightness to full and see a raster, indicating that as least elements of the power supply are working... Still learning about the Pet but a raster on the screen would be a good start.

    Cheers,

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  8. #28

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    I've never messed with a CRTC pet, but I suspect the monitor might not even power up without a video signal from the CRTC. And you shouldn't get that unless the boot code runs correctly.

  9. #29
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    Quote Originally Posted by KC9UDX View Post
    I've never messed with a CRTC pet, but I suspect the monitor might not even power up without a video signal from the CRTC. And you shouldn't get that unless the boot code runs correctly.
    Probably true. The Editor ROM is responsible for initializing the CRTC registers to configure the screen parameters on boot. As far as I know, the CRTC chip has no default register values (I'll assume all zeroes on reset) so the H and V sync's will not be set properly.

    Steve
    WANTED: CBM-II hardware or software, PET software

  10. #30
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    Quote Originally Posted by TRS-Ian View Post
    I've checked the fuse and it's OK, but the computer shows absolutely no signs of life which is why I plan to start with the voltages.
    Ian,
    After the voltage tests, since it seems that your ROMs are on sockets, for a quick and dirty test, replace the kernal ROM at UD6 with a 2532 EPROM programmed with pettest2.bin. It is a RAM memory test that does not depend on having good zero page RAM. After power-on, it takes quite a few seconds to get a screen response due to the fact the CRT Controller initialization routine is tacked on to the end of the memory test before it loops back to the start. If the PET is well enough to execute instructions, you will will see some screen activity.

    The 4k binary file can be found somewhere on zimmer's or download it from here. A text file of the code can be found here.
    -Dave

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