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  1. Replies
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    If you order some parts, make sure you get a few...

    If you order some parts, make sure you get a few 40 pin DIP sockets with good machined pin sockets. Since both PIA chips do not work in that socket, the socket may be bad as Dwight as mentioned.
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    It is the PIA in the C7 socket that will issue...

    It is the PIA in the C7 socket that will issue the interrupt. Does this happen with both 6520's in that location? Is C7-pin 18 (Video On) pulsing? That signal will trigger the IRQ every cycle of the...
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    ditto. I thought I lost a setting.

    ditto. I thought I lost a setting.
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    Emmanuel, For fixing very old computers, do...

    Emmanuel,

    For fixing very old computers, do not buy an EPROM Programmer unless its states that it can program the 2716 and 2732 chips and hopefully the 2532 chips. The 2532 is a pin for pin...
  5. Thread: PetVet

    by dave_m
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    Mike at bitfixer has a new part called ROMulator...

    Mike at bitfixer has a new part called ROMulator that has replaced the PETVet.

    To reprogram the Atmel microcontroller, you would need PHP and run a custom script file to create the load file....
  6. Thread: VHDL resources

    by dave_m
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    This is really good information. Thanks for...

    This is really good information. Thanks for posting. Previous to these texts, most of the books I've tried on VHDL seemed way to advanced/confusing for me. These books look understandable.
    -dave_m
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    Pip, CBM4032 works OK and puts the 40 character...

    Pip,
    CBM4032 works OK and puts the 40 character image starting 20 characters in, so it is in the middle of the screen. But you have to remember to do it before loading any game. A reset is required...
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    It is possible that the set up time from address...

    It is possible that the set up time from address lines in to data out is out of spec slow. You can not tell that from your manual tester. Those old parts had high internal delays.

    The open...
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    Dwight, I broke down and bought the gadget. It...

    Dwight,
    I broke down and bought the gadget. It works really nice. The software is going to take a little time to learn well. My Tektronix 453 scope is very upset with me...
    -Dave
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    The Rockwell parts work fine. Don't forget to...

    The Rockwell parts work fine. Don't forget to search for the Motorola 6820/6821 parts. I don't know about the Western Digital parts, but the website says the 65C21N is compatible with the old NMOS...
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    daver, Back in the day, they used a lot of...

    daver,
    Back in the day, they used a lot of asynchronous combinational logic as shortcuts. You must have converted it all to a synchronous logic state machine design to have a chance for it to work...
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    Pip, Another thing to look at would be C752...

    Pip,
    Another thing to look at would be C752 (0.01 uF, 500 V). One side should be around 190 V and the other at 400 V, yet the 400 V side is at 218 V. Bad cap?
    -dave_m
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    Daver, AGC? Are we talking the Apollo Guidance...

    Daver,
    AGC? Are we talking the Apollo Guidance Computer from the moon shot? Did it fit in one chip?
    -dave_m
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    Pip, Actually nothing; UB12 is monitoring for...

    Pip,
    Actually nothing; UB12 is monitoring for the diagnostic pin being held low on the User Port on power up. If so, the programs jumps to the machine language monitor. For some unknown reason, the...
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    So jitter went away with 50 Hz Edit EPROM? And I...

    So jitter went away with 50 Hz Edit EPROM? And I see you installed everything in the PET chassis. Super good work, Giovi!

    Make sure you squirrel away all documentation of this mod in a ziplock...
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    Giovi, Nice that you fitted everything in the...

    Giovi,
    Nice that you fitted everything in the PET chassis. Congratulations! Please keep schematics and all information on the modification inside the PET chassis as documentation for future users of...
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    It's attempting to load from disk, but without...

    It's attempting to load from disk, but without UB16, there is no IEEE port.
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    OK, I see that the early version of the 8032 did...

    OK, I see that the early version of the 8032 did not invert the VSYNC. Perhaps it used a different video board?

    Try the 50 Hz EDIT ROM and see if that helps the jitter you are seeing. Use a 2716...
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    Pip, You are correct. For long term reliability,...

    Pip,
    You are correct. For long term reliability, aerospace PCB assemblies, after cleaning and before conformal coating, must undergo some 24 hours in a thermal-vacuum station undergoing simultaneous...
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    With the big chips missing 6520s & 6522 the...

    With the big chips missing 6520s & 6522 the Commodore welcome screen should appear, but nothing else will run. The UB12 6520 PIA provides the needed 60 Hz interrupt. The UB15 6522 VIA provides the...
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    Ha! OK, but I was thinking of trying a...

    Ha! OK, but I was thinking of trying a Composite-to-VGA adapter (I just ordered) to avoid buying an old TV. I might run into the same issues you did with the CGA adapter. Now that will be funny!...
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    Mike, Yes, and it hasn't escaped my notice that...

    Mike,
    Yes, and it hasn't escaped my notice that your reminder about PET polarity jumpers got Giovi to check his jumper configuration and fix his problem. Daver, Hugo and I do all the work and you...
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    Good work. But you may be reading an old...

    Good work.
    But you may be reading an old schematic. On the latest schematic (Universal 2), both jumpers are tied to separate pull up resistors. By grounding jumper 3, the HSYNC is inverted to...
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    I can't believe that Pip is getting so much done...

    I can't believe that Pip is getting so much done without a scope. Good work.
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    Hugo, Will a circuit like this do? The LS244...

    Hugo,
    Will a circuit like this do? The LS244 buffers have a lot of drive capability with I out (low) of 24 mA sink and a I out (high) of 15 mA source. That will certainly drive the resistor network...
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