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Professional Dos Nachbau

  • Tom,


    Thanks for continued help - I was out for a little but am back now.


    I tried out the JiffyDOS as you requested - and this does NOT seem to work correctly - check the picture.

    I can confirm same results on an alternative 1541 drive, both at correct drivespeed. Also I have built a SECOND PCB, same results.


    What would be a next thing to try?


  • For clarity on the previous post, JiffDOS DOES read an original diskette, it DOES not format correctly (as you can see in the picture) - it DOES seem to be able to write a file to that messed up formatted floppy, and DOES read the same file back correctly.

    Very strange


    Especially if both boards do so. Then I think it can not really be a soldering error. How are the jumpers JP3 plugged? Do you have tried that with rotated jumpers JP3 (1571-Mode)?

    Because: If JP3 is in 1571-Mode and JD-Mod , the PCB only replaces ROMs $C000-$FFFF and RAM. And if you also plug JP1-2 and JP1-3, original RAM is used and also $C000-$DFFF is original.

    And when you use JD, please unplug parallel cable also to exclude this as a cause as well.

  • Tom,


    Strange indeed.....


    How are the jumpers JP3 plugged? Do you have tried that with rotated jumpers JP3 (1571-Mode)?

    Same result in both cases, no difference

    Because: If JP3 is in 1571-Mode and JD-Mod , the PCB only replaces ROMs $C000-$FFFF and RAM. And if you also plug JP1-2 and JP1-3, original RAM is used and also $C000-$DFFF is original.

    Same result in both cases, no difference

    And when you use JD, please unplug parallel cable also to exclude this as a cause as well.

    Same result in both cases, no difference



    I am beginning to suspect one of the logic ICs - I only got same models from bulk batch - and I am leaning to obtaining replacements from elsewhere to exclude this from being the cause - thoughts?

  • I am beginning to suspect one of the logic ICs - I only got same models from bulk batch - and I am leaning to obtaining replacements from elsewhere to exclude this from being the cause - thoughts?

    Hm. I'm not so sure that this is a problem of the IC's ...

    If so, IC 5,6 and 7 would be the suspects as they mix up the addresslines of ROM and RAM on the PCB. This is the HW-GCR-decoder. Normaly inactive when using different DOS than PD.

    I sent you the circuit diagram via email. IC 3 is only inverting one signal for this circuit. This should be easy to test. IC 2 and 4 and rest of IC3 have no effect to the circuit when JP3 is in "1571 mode".


    I'm a bit clueless at the moment to be honest....


    Can you please send some more photos of the PD PCB and from the whole Floppie boards with mounted PD?

  • I don't see anything wrong or extreordinary ...


    And I can't think of anything on the PD that would produce an error like this.


    Suggestions:

    Please replace original ROM in the floppy with JD (PD PCB NOT plugged in) and try formatting again.


    Try if it makes a difference if the VIA is in the parallel adapter or plugged in directly.


    If this works, the problem really is on the PD PCB.


    Otherwise you have to have another look on your floppies ...


    Btw: Did you try to cross-exchange the VIAs?

    I found a thread where a problem with formatting was reasoned in a defect VIA 6522...


    And another thing:

    Your 6502 and your 6522 are both only for 1MHz. This can NOT be the Problem you have right now,

    but it CAN (maybe) lead to difficulties in 2MHz operation mode later.

  • HI.


    Any news?


    Today I had a Déjà-vu.

    I tried to format a disk and it alwasy ended with an error at the end.


    The only problem was: I dropped a (connected) signal cable on the area near the head-connector on the floppyboard.

    This was enough to interfere with the head signals. Cable removed, everything ok again ...


    And I now remember, once I dropped the cable from PD to the two color LED there, I also had some trouble

    reading and writing ....