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Thread: Commodore pet 3032 screen full of lines

  1. #301

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    Quote Originally Posted by daver2 View Post
    Interesting...

    Pin 15 (/CAS) is what I expect. Pin 4 (/RAS) is not...

    I expect both of these signals to be mainly up at 5V and dip down to 0V when they are active. With the timebase at the speed it is, I expect to miss some of the low going signals and sometimes some of the detail. This is what I see for /CAS but not for /RAS.

    Can you set the timebase to something a bit quicker (my oscilloscope can go up to 10 microseconds per division (10 us/div) and recheck the signals on both pins please).

    If that looks promising, we will probably switch to a manual trigger mode next.

    Gut feeling tells me we may have a problem with the /RAS signal, but (there again) we may not be 'teasing' the signal out so we can see it...

    Dave

    Hi Daver2,
    thank you for your patience and for continuing to work on my pet
    Hi tested again but on UI2 PIN 4,
    the minimum value I can see something in is 1ms!
    20191009_174627.jpg
    20191009_174721.jpg

  2. #302
    Join Date
    Jun 2012
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    UK - Worcester
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    >>> thank you for your patience and for continuing to work on my pet

    No problem, I find these logic puzzles more interesting than (for example) crossword puzzles etc.!

    I can believe pin 15 ok.

    Pin 4 (/RAS0) does look strange to me. Have you actually tried this pin with a timebase of 10 us/div or not? If not, it would be interesting for you to try anyhow. Sometimes (if the timebase is too slow - e.g. 1 ms/div) the signal may disappear, but then come back again as you speed it up! Don't be afraid to adjust the timebase knob to be faster to see what happens!

    If we suspect something is wrong with the /RAS0 signal (pin 4) - and I do - can you also check UG1 (SN74LS08) pins 11, 12 and 13 with a timebase of 10 us/div (leave the timebase of the oscilloscope at this setting from now until told differently). For your information, gate UG1 is the gate that drives the /RAS0 signal (via a low-value resistor) and can be seen on the schematic at http://www.zimmers.net/anonftp/pub/c...N/320349-6.gif (upper right).

    Dave

  3. #303

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    Quote Originally Posted by daver2 View Post
    >>> thank you for your patience and for continuing to work on my pet

    No problem, I find these logic puzzles more interesting than (for example) crossword puzzles etc.!

    I can believe pin 15 ok.

    Pin 4 (/RAS0) does look strange to me. Have you actually tried this pin with a timebase of 10 us/div or not? If not, it would be interesting for you to try anyhow. Sometimes (if the timebase is too slow - e.g. 1 ms/div) the signal may disappear, but then come back again as you speed it up! Don't be afraid to adjust the timebase knob to be faster to see what happens!

    If we suspect something is wrong with the /RAS0 signal (pin 4) - and I do - can you also check UG1 (SN74LS0 pins 11, 12 and 13 with a timebase of 10 us/div (leave the timebase of the oscilloscope at this setting from now until told differently). For your information, gate UG1 is the gate that drives the /RAS0 signal (via a low-value resistor) and can be seen on the schematic at http://www.zimmers.net/anonftp/pub/c...N/320349-6.gif (upper right).

    Dave
    20191009_194729.jpg
    20191009_195435.jpg
    20191009_195519.jpg

  4. #304
    Join Date
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    Thanks,

    Completely not what I am expecting I am afraid.

    Can I suggest we move further back (by one integrated circuit) and, if we don't get any sense from the oscilloscope, we wait until I get this 8032 into the workshop (aka conservatory !) and I will have a go? I then should be able to suggest some definitive oscilloscope settings or we have to admit defeat in the short term and get some better test equipment.

    The next set of pins of interest would be UH1 (74S74) pins 1, 2, 3, 6, 8, 11 and 13.

    If we get no joy on any pin (...) it may be worth slowing the timebase down on the oscilloscope and see if you can see anything at all on UH1 pin 13.

    Dave

  5. #305

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    Quote Originally Posted by daver2 View Post
    Thanks,

    Completely not what I am expecting I am afraid.

    Can I suggest we move further back (by one integrated circuit) and, if we don't get any sense from the oscilloscope, we wait until I get this 8032 into the workshop (aka conservatory !) and I will have a go? I then should be able to suggest some definitive oscilloscope settings or we have to admit defeat in the short term and get some better test equipment.

    The next set of pins of interest would be UH1 (74S74) pins 1, 2, 3, 6, 8, 11 and 13.

    If we get no joy on any pin (...) it may be worth slowing the timebase down on the oscilloscope and see if you can see anything at all on UH1 pin 13.

    Dave
    20191009_211348.jpg
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    20191009_211542.jpg
    20191009_211716.jpg
    20191009_211815.jpg
    20191009_211924.jpg
    20191009_212042.jpg
    _20191009_195519.jpg

  6. #306
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    Jun 2012
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    Why has the timebase changed from the 10 us/division I specified back in post #302?

    Can you repeat the UH1 pin measurements again with the timebase set to 10 us/div? Thanks.

    Dave

  7. #307

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    [QUOTE=daver2;590120]Why has the timebase changed from the 10 us/division I specified back in post #302?

    Can you repeat the UH1 pin measurements again with the timebase set to 10 us/div? Thanks.

    Dave[/QUOTE
    I can t see nothing at 10us.....

  8. #308
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    OK, thanks.

    Can I suggest we take a break until I get back with the 8032 and we will pick up with this thread again?

    How does this sound?

    Dave

  9. #309

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    Quote Originally Posted by daver2 View Post
    OK, thanks.

    Can I suggest we take a break until I get back with the 8032 and we will pick up with this thread again?

    How does this sound?

    Dave
    Ok thanks!But in this time can i try to change first bank ram maybe??

  10. #310
    Join Date
    Jun 2012
    Location
    UK - Worcester
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    It's your machine, you can do whatever you like!

    Let me know how it goes.

    Good luck!

    Dave

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