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Thread: Commodore MMF 9000 / SuperPet 9000 Monitor problem: Help needed!

  1. #1

    Default Commodore MMF 9000 / SuperPet 9000 Monitor problem: Help needed!

    Hello everyone!

    I have a problem with my Commodore MMF 9000: Everytime i turn it on, it displays a green Screen with Horiontal lines and a blinking black box on the sixth line (Only when i select the 6502 processor). By looking at the VICE Emulator, you can tell that the sixth line is the default input line when you start the computer, so i think BASIC in general is working. I also got another bug when I select the 6809 processor: The horizontal lines are now interrupted by Black boxes everywhere.
    However, I really donīt know how to fix it.

    Thank you in advance!

    IMG-20181102-WA0002.jpg
    IMG_20181102_112317.jpg

  2. #2

    Default

    Quote Originally Posted by ZapdoZ View Post
    Hello everyone!

    I have a problem with my Commodore MMF 9000: Everytime i turn it on, it displays a green Screen with Horiontal lines and a blinking black box on the sixth line (Only when i select the 6502 processor). By looking at the VICE Emulator, you can tell that the sixth line is the default input line when you start the computer, so i think BASIC in general is working. I also got another bug when I select the 6809 processor: The horizontal lines are now interrupted by Black boxes everywhere.
    However, I really donīt know how to fix it.

    Thank you in advance!

    IMG-20181102-WA0002.jpg
    IMG_20181102_112317.jpg
    I'm not so sure it's a monitor circuit problem. Looks like more a video circuit failure inside the PET's motherboard, like dead chargen ROM or stuck serial register's output.

    Frank IZ8DWF

  3. #3

    Default

    Thanks for the reply! So how do i find out what exact chip is broken and how do i repair/replace it? I donīt think these chips are sold these days ;D

  4. #4
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    2,380

    Default

    Welcome to VCFED ZapdoZ - as this is your first post.

    I think a bit of your post got 'chopped off' somehow. How did you get the boxes on the screen? As I now have two fault modes and (if you can provide details of how you got the second fault mode) two initiators, I may be able to make a more educated diagnosis.

    Where are you based?

    Dave

  5. #5

    Default

    Quote Originally Posted by daver2 View Post
    Welcome to VCFED ZapdoZ - as this is your first post.

    I think a bit of your post got 'chopped off' somehow. How did you get the boxes on the screen? As I now have two fault modes and (if you can provide details of how you got the second fault mode) two initiators, I may be able to make a more educated diagnosis.

    Where are you based?

    Dave
    Hi Dave!

    So the SuperPet has switches on the side where you can select different boot modes / usages of chips. I can select using the 6502 or the 6809 processor. The first picture shows the computer booting up with 6502 selected (the box blinks just like the green box in BASIC). The second one shows the computer booting up with 6809 selected - the boxes appeared themselves.

    I live in germany

  6. #6

    Default

    Is this a one board or two board SuperPet ?

    I would remove the additional board(s) and put the 6502 back into the vacant socket and power up ... to see what happens. If you are not familiar, the SuperPet add-on boards are interfaced to the 8032 motherboard on the 6502 socket. The 2 board versions may also have additional switches that connect to the expansion ROM sockets. Be careful removing the (grey) ribbon cable from the 6502 socket to avoid bending pins.

    The character rom is a special one for the SuperPet - if it is OK then that will become evident when you put the computer back to normal 8032 mode (re-seat the character rom and also post the serial number of the chip - I think it should end with -10)

    Interesting to know where you are located and the basic history of your SuperPet (MMF9000). I have a working SuperPET so will try to assist you with others here on the forum.

    Cheers

    Quote Originally Posted by ZapdoZ View Post
    Hello everyone!

    I have a problem with my Commodore MMF 9000: Everytime i turn it on, it displays a green Screen with Horiontal lines and a blinking black box on the sixth line (Only when i select the 6502 processor). By looking at the VICE Emulator, you can tell that the sixth line is the default input line when you start the computer, so i think BASIC in general is working. I also got another bug when I select the 6809 processor: The horizontal lines are now interrupted by Black boxes everywhere.
    However, I really donīt know how to fix it.

    Thank you in advance!

    IMG-20181102-WA0002.jpg
    IMG_20181102_112317.jpg
    Last edited by AndyG; November 2nd, 2018 at 12:23 PM.

  7. #7
    Join Date
    Jun 2012
    Location
    UK - Worcester
    Posts
    2,380

    Default

    I have looked at your initial post with a different computer - and I now see the AWOL text! It is when you switch into 6809 mode you get the interesting 'block' effect.

    My first thought is that what is being displayed on the screen is effectively a solid green block or a solid black block depending upon what character is stored on the screen.

    Let me think a bit more...

    Unless you know what you are doing - I would strongly advise against removing the SuperPET boards at this point in time. Just my advice.

    Can I suggest first selecting 6502 mode and (assuming it is BASIC that is running - but we can't see it) try and type some known letters on the keyboard (e.g. "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789 and see what is displayed.

    If the 6502 has 'crashed', 'halted' or is otherwise not running - you will see nothing further.

    If you get characters/blocks or whatever displayed - this may give us a further clue going forwards.

    Admittedly, the SuperPET could be causing the issue itself - so removing the additional card(s) may give you a working 8032 and we can work from there. It may be a dirty connector - in which case just disturbing the connectors a little but may also cure the problem.

    When was this last working? Has it been working and suddenly gone faulty - or have you pulled it out of the loft after a long period and just powered it up? Details will help.

    Have you got access to any test equipment (in order of: multimeter, logic probe, oscilloscope etc.)?

    Dave

  8. #8

    Default

    Yes, the 6502 screen shown in the photo 1 is what you get when the character rom is not there or 'bad' . You would expect to see the same screen for 6809 also though with the cursor lower down, and not the block effect.

    The serial number for the character rom ends in -01 (not -10) as said in last post)

    Agree with Dave, more background information would be great as well as knowing if it is a 2 board or 1 board SuperPET.

    Quote Originally Posted by iz8dwf View Post
    I'm not so sure it's a monitor circuit problem. Looks like more a video circuit failure inside the PET's motherboard, like dead chargen ROM or stuck serial register's output.

    Frank IZ8DWF

  9. #9

    Default Background Information / Keyboard

    Thanks for all your replys!

    So the MMF was used in the 80s by my dad in his office in germany. He told me it smoked one day and then he never turned it on again. It was stored in the basement under a couple of plastic bags for about 30 Years.
    I checked the board and found no capacitor that blew up / other burn spots, so i decided to turn it on again.

    The MMF has 3 Boards (Photo in attachment)

    I decided to press some keys but the most of the keyboard wasnīt working. I only got black boxes on the screen. I only got a bad photo of it but you can see it.

    I only got a multimeter as test equipment.

    -ZapdoZ

  10. #10

    Default

    Forgot to post the photos in my last reply sorry
    IMG_20181103_122144.jpgIMG_20181103_085829.jpg

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