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Thread: CBM 3008 / 2001-8N won't boot.

  1. #1

    Default CBM 3008 / 2001-8N won't boot.

    I'm currently trying to repair a Commodore 3008 or 2001-8N (both names are on the machine), but I'm having trouble finding any troubleshooting tips online so I thought I'd ask here. My 3008 isn't showing any lifesign when I turn it on. Absolutely nothing happens. I already looked for blown capacitors/fuse, any broken traces or loose cables. I'm not an expert, so I hope somebody on this forum is or knows where to find one who could help me.
    Btw. it's a PAL model if that helps.

  2. #2
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    Welcome to VCFED.

    There is plenty of information about fixing PET’s on this thread !

    In fact, I have an 8032 on my bench at the moment to repair and I have just taken the first steps this morning.

    First off, can you read electronic schematics? Second, do you have any test equipment (e.g. a basic multimeter, logic probe or oscilloscope)?

    As you are new, you will be moderated for the first few posts, so don’t loose heart if your post doesn’t make it for a few days. The mods are busy and this is not a paid job! The benefit of moderation is that it keeps the spam significantly low on the board.

    The first thing is to disconnect the monitor cable from the mainboard. It is very easy to damage the monitor due to a malfunctioning main board. You don’t want to damage things further do you?

    The next thing is to disconnect the transformer from the main board by disconnecting this connector from the main board. I put the connector and cable into a small plastic bag to stop it inadvertently shorting out to anything.

    The next thing to do is to use a multimeter (set to AC Volts) to read the voltage produced by the transformer.

    I thought I would post the first few steps here for you to read. Is what I am saying understandable or not? If not, I will take it much more slowly once I know you have some basic test equipment.

    Dave

  3. #3
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    Does this memory schematic describe your configuration of memory chips 6 ea 2316 ROMs and 16ea 2114 RAM chips? Or is it another type of memory chips?

    http://www.zimmers.net/anonftp/pub/c...1/320137-2.gif

  4. #4
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    Quote Originally Posted by dave_m View Post
    Does this memory schematic describe your configuration of memory chips 6 ea 2316 ROMs and 16ea 2114 RAM chips? Or is it another type of memory chips?

    http://www.zimmers.net/anonftp/pub/c...1/320137-2.gif
    That'd be one of the four versions of the 2001 (no 'N' suffix); the 2001Nx, 30xx and the 9" screen version of the 40xx all use the 'Dynamic' PET board:
    http://www.zimmers.net/anonftp/pub/c...01N/index.html

  5. #5
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    Hi Mike,
    But what is confusing is that he has only 8K of RAM. Dynamic RAM would come in 16K or 32K.

  6. #6
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    There was an 8K dynamic PET (see http://www.zimmers.net/anonftp/pub/c...ynamic_pet.pdf) using 8K*1 DRAMs.

    Dave

  7. #7
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    Quote Originally Posted by dave_m View Post
    Hi Mike,
    But what is confusing is that he has only 8K of RAM. Dynamic RAM would come in 16K or 32K.
    I think for a while during the RAM shortage days manufacturers even including IBM were re-testing defective 16K chips and sorting and using them as 'upper 8 OK' or 'lower 8 OK'.

    See:
    https://www.flickr.com/photos/156365529@N03/34857000653

    But we should really know the part numbers of the RAM chips to be sure.
    Last edited by MikeS; February 21st, 2020 at 12:12 PM.

  8. #8
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    Quote Originally Posted by daver2 View Post
    There was an 8K dynamic PET (see http://www.zimmers.net/anonftp/pub/c...ynamic_pet.pdf) using 8K*1 DRAMs.
    I have one of those machines; the chips were labeled 4108, and several of them were bad when I got it. (Actually, to make it more confusing, the board is in a chicklet case, not a "real keyboard" 2001N. It came from a warehouse formally owned by a company that supplied computers to the Berkeley school district so I think it may have been some kind of refurbished monstrosity.) The board even has a hole drilled through the second RAM bank to prevent it from being upgraded by populating the sockets.

    I'm pretty sure you can just sub a 4116 with no changes if one is bad, although it doesn't sound like we're anywhere near that point on this troubleshooting adventure. A friend of mine did the fixing on my Chicklet machine, and he opted to disable the +12v and -5vs lines and sub 4164s all the 4108s because he had them lying around. (And in the process the machine became a "2001-16"? It's been on my to-do list to see about coming up with a devious way of using the second 16k select line to enable 32k in the single bank.)
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  9. #9

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    Quote Originally Posted by daver2 View Post
    First off, can you read electronic schematics? Second, do you have any test equipment (e.g. a basic multimeter, logic probe or oscilloscope)?
    Yes and No. No I can't read schematics (only to a certain degree), but yes i have a multimeter, I can get a logic probe if necessary and I have an old oscilloscope lying around.
    I totally get what you're saying and thank you for helping. I'll do the first few steps you already wrote. By the way if there is any misspelling in my posts I'm not a native speaker.
    Please post the following steps.

    PS: Sorry for taking so long I had a busy weekend.

  10. #10

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    Quote Originally Posted by MikeS View Post
    But we should really know the part numbers of the RAM chips to be sure.
    The part numbers should be on the RAM chips itself right?
    Does a photo of the mainboard help to identify them?

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