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guus.assmann

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Posts posted by guus.assmann

    Atari 1050: Intermittent Moton On (and activity LED)

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann
    Typos and added text.

    That disk is only usefull for: Alignment.

    This means making sure the stepper motor sends the head to the correct place.

    It's no use to diagnose any hardware faults.

    Manufacter if memory serves well is Dynatec.

    The disk has a trace that has been written a-symetrical and will display a "cat-eye" on an oscilloscope.

    In the many drives I had to repair, I used it once or twice.

     

    BR/

    Guus

    • Like 1

    MegaFile30 KALOK KL330 blown capacitor

    in Atari ST/TT/Falcon Computers

    Posted · Edited by guus.assmann
    Addes P.S.

    Hello,

    My advice, just cut out the capacitor and retest the unit.

    It's a Tantalium capacitor and most likely used for decoupling / buffering of the supply.

    And in that application it's mostly redundant.

    This also means the value is not so importat, only the working voltage. (and the polarity of course)

    Be aware that more of these Tantaliums may fail or have failed.

     

    BR/

    Guus Assmann

     

    P.S.
    Test my assumprion by following the traces or measure with an Ohm-Meter / Buzzer for low resistance.

    • Like 2

    I think Rockwell SALLYs (6502C) are unjustly getting a bad reputation. I've come around that they are equally good parts.

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann
    Added a P.S. note.

    Hello all,

     

    A little back to the topic of the failing CPU's.

     

    During the introduction of the 600XL and 800XL in Europe, I worked for Atari in the Benelux.

    And I did repair many XL units.

    There was an issue with very specific production dates of CPU's produced in Mexico. (Ony two or three dates if I remember correctly.)

    Mind you, not all would fail.

    The test I devised was simple.

    Just open the unit and lay the CPU bare.

    Start the unit and let Basic come up.

    Enter the line:

    For x=0 to 100000: print x; "Atari test": next x.

    When this was running, use a hair dryer to heat up the CPU.

    The CPU never got so hot that it couldn't be touched !

    When the CPU was warm, the display would freeze if it had the issue.

    However a Reset would restart the unit without fail.

    Sometimes it would pass this test and then there was another defect in the unit.

    I never found other CPU's with this behaviour. In my opinion it had to do with the timing of the Halt input.

    As this is not present in any 400 or 800 board, those were not affected at all.

     

    This is my experience as technician.

     

    BR/

    Guus Assmann

     

    P.S.

    This discussion is quite arbitrary anyway... 🙂

     

    • Like 2

    Happy Warp 1050 7.1 Schematic

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann
    Typos and added text.

    Hello reifsnyderb,

     

    The schematics are either from cloned boards or reverse engineerd from a clone board.

    If you look at the memory map that is decoded by any of the address decoders, you'll find they all do the same.

    And to the best of my knowledge / experience, the track display was a hack by a private person.

    The displays are just put on a address in the memory map. (With lots of "shadow" addresses.

    In fact, all the "shadows" are a result of incomplete address decoding, based on chip-count.

    Either because of cost, or because of board-size.

     

    The use of a track-decoder is in analysing disk-protection scemes.

    And of course it looks way cool 😃

     

    You could use a GAL device to do a decoder that can be changed.

    I've once made that design and a board, but never got to make the logic in the GAL.

     

    I do own one original Happy board. (Got it as a gift)

    And I never got to use it. It arrived "in the middle" of creating the MegaSpeedy1050 boards.

     

    Best regards,

    Guus Assmann

    • Like 1

    1050 Happy Warp with LED display (v3?)

    in Atari 8-Bit Computers

    Posted

    Hello reifsnyderd,

     

    Software is not my strongsuit.

    I have no idea why any Rom works or doesn't. I didn't look into that.

    What I do know, is that the display is only a memory location to write to.

    reading it has no value. So I think it's very unlikely that not having the display prohibits the unit from working.

     

    You can try to ask Hias.

    He made the software for the MegaSpeedy and analized a lot of Eproms in drive units.

     

    BR/

    Guus Assmann

    • Thanks 1

    Happy Warp 1050 7.1 Schematic

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann
    Extra info

    Hello,
     

    Have not read this tread fully.

    However, here's my schematics of Happy's. (With a track display, but that's irrelevant)

    All of these versions do work, I've also made PCB's and build a few.

     

    As for write protect on the floppy, the drives I know (Shugart bus) have a write protect that cannot be influenced by any program in a floppy controller.

    So the write protect on the disk activated/deactivates a signal that's commonly called "write gate".

    If inactive, the write amplifier to the head is deactivated.

    If I remember correctly, this mechanism is also in the 1050 hardware.

     

    The extra Ram on the PCB consisted of 3 pieces 2K ram in the very first PCB's.

    Once the 8K ram became available and affordable, this was used.
    BR/

    Guus Assmann

    HAPPY2.pdf HAPPY2a.pdf HAPPY4.pdf

    • Like 3
    • Thanks 1

    Open 6810 Doubler PCB (for 1050 US Doubler Upgrade)

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann

    Hello Larryleffaovell,

     

    Thanks for posting the Zip with the Gerber data.

    Can you please also post the KiCad design file?

    Then I can see if I can panalize it to fit some in a 100 x 100mm PCB.

    This size is very cheap with JLCPCB and I also found how I can get the V-Scoring to work.

    Of course I'll post the results here again....

     

    BR/

    Guus Assmann

    • Like 1

    I need a 6522 VIA to repair a Black Box

    in Atari 8-Bit Computers

    Posted · Edited by guus.assmann

    I've looked but cannot find the original ordering numbers anymore.

    Obviously, the WDC parts is called WDC65C22. But the suffix is about the shape of the housing.

    They do exist in DIL40 and Quad-housing. (PLCC-44)

    Looking at Mouser, the number I get is W65C22NTPG-14  Place 955- in front of this and you have the Mouser order number.

    For me, they're listed at 10,21 Euro and more than 1700 in Stock.

     

    Not sure about the hardware mod, but I think it's only changing the clock speed to the Uart (65C51)

    For that, 955-65C51N6TPG-14 at 7,31 Euro and 228 in stock

    • Thanks 1

    I need a 6522 VIA to repair a Black Box

    in Atari 8-Bit Computers

    Posted

    Also, other than the change to the 6551 circuit, there is no possibillity to have a higher speed.

    The computer is just not fast enough.

    The only way would be, to use a 65C816 at 14Mhz and have that handle a Uart at this epeed.

     

    All Data to the BB I had, including the PCB design has been given to Fox.

    The 1488 and 1489 can e exchanged by a MAX 232 very simple.

    The only thing is, that one MAX has 2 input and  2 output channels. So a MAX 238 may be needed.

     

    BR/

    Guus

     

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