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Thread: PET 2001 Issues

  1. #11
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    Both PETs have a 320351 motherboard

  2. #12
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    Ah, so that makes it a 2001N.

    The IEEE 488 6520 in this case is UC6 and the KEYBOARD/DIAG 6520 is UC7.

    Dave linked to the correct place back in post #9...

    Dave

  3. #13
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    Ah, ok. So I'll try swapping those? Is there anyone who can write new roms for these machines if they need them?

    Also out of curiosity what does the N signify in 2001N?

  4. #14
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    The 2001 is the ‘original’ PET. There are a number of mainboard variants, but the main feature is static RAM.

    The 2001N is the ‘next generation’ PET. The main feature is dynamic RAM.

    If memory serves me correctly, the 2001 has a white phosphor monitor and the 2001N has a green phosphor monitor.

    You can’t write new ROMs, you have to buy them...

    The alternative is to program an EPROM and use a small adapter board. The adapter boards are available on the internet, and suitable EPROMs can be programmed (if it turns out to be one of those). We have a diagnostic EPROM available to replace your EDIT ROM that will tell us if the ROMs are good or bad.

    Dave

  5. #15
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    Do you have a link to the diagnostic EPROM? I think I definitely need one of those, and probably the adapters too. I swapped UC6 and UC7 and nothing changed

    Update: swapping chips around I believe I found the issue with my uncle's- one of the 6520's. Both of mine seem good and work prefectly in my uncle's. Mine works just fine apart from no blinking cursor and not being able to type with either neither UC6 or UC7 populated or with only UC6 populated. With UC7 populated it always throws the same error
    Last edited by RadRacer203; January 25th, 2020 at 02:36 PM.

  6. #16
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    Quote Originally Posted by RadRacer203 View Post
    Do you have a link to the diagnostic EPROM? I think I definitely need one of those, and probably the adapters too. I swapped UC6 and UC7 and nothing changed

    Update: swapping chips around I believe I found the issue with my uncle's- one of the 6520's. Both of mine seem good and work prefectly in my uncle's. Mine works just fine apart from no blinking cursor and not being able to type with either neither UC6 or UC7 populated or with only UC6 populated. With UC7 populated it always throws the same error
    Did you read message#9, I asked if you can program a 2716 EPROM. If not, I can send you one programed with the daver2 test code. It will not need an adapter to plug into the D8 socket. The binary file can be found here (daver2 will know if this one is the latest) https://drive.google.com/drive/folde...KB9NAY2XYqNUR6

    C7 is an important device; it handles the keyboard, it generates the 60 Hz interrupt that blinks the cursor and scans the keys, and also checks for a diagnostic pin on the user port that if it is grounded will cause the PET to Call the machine language monitor so you will have to check if C7 pin 9 is grounded.

  7. #17
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    Quote Originally Posted by dave_m View Post
    Did you read message#9, I asked if you can program a 2716 EPROM. If not, I can send you one programed with the daver2 test code. It will not need an adapter to plug into the D8 socket. The binary file can be found here (daver2 will know if this one is the latest) https://drive.google.com/drive/folde...KB9NAY2XYqNUR6

    C7 is an important device; it handles the keyboard, it generates the 60 Hz interrupt that blinks the cursor and scans the keys, and also checks for a diagnostic pin on the user port that if it is grounded will cause the PET to Call the machine language monitor so you will have to check if C7 pin 9 is grounded.
    Must have missed that, I want to be able to write eproms but I'm not set up yet. Might be better to just have a ready made one for this project. I'm thinking something related to the keyboard or diagnostics is wrong and c7 is detecting it, or however that works. This is my only Commodore so I'm not familiar with them at all. Also, is there any good place to get a new 6520 for my uncle's machine? Ebay has one for nearly $400....
    Last edited by RadRacer203; January 25th, 2020 at 04:54 PM.

  8. #18
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    Ok, mine is working now. It puts me into the diagnostics when the floppy drive is plugged the left (when facing the rear) port but not the right

  9. #19

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    Quote Originally Posted by RadRacer203 View Post
    Must have missed that, I want to be able to write eproms but I'm not set up yet. Might be better to just have a ready made one for this project. I'm thinking something related to the keyboard or diagnostics is wrong and c7 is detecting it, or however that works. This is my only Commodore so I'm not familiar with them at all. Also, is there any good place to get a new 6520 for my uncle's machine? Ebay has one for nearly $400....
    Anchor Electronics has a 6520A. I believe it should be compatible. It is a lot cheaper than $400.
    Dwight

  10. #20
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    Quote Originally Posted by RadRacer203 View Post
    Ok, mine is working now. It puts me into the diagnostics when the floppy drive is plugged the left (when facing the rear) port but not the right
    The left port is the user port. You were shorting the diagnostic pin!

    The right port is the only IEEE-488 port.

    Please find a book on the PET on the internet to refresh yourself on the workings of the PET.

    PET connectors.jpg
    Last edited by dave_m; January 25th, 2020 at 11:29 PM.

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