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  1. After some months I managed to buy the keyboard...

    After some months I managed to buy the keyboard on ebay and I reverse engineered the protocol a bit.
    Since I already I own the keyboard, I will not build an adapter, but maybe someone will be in...
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    I donít think it should ever pass if chip is...

    I donít think it should ever pass if chip is faulty even for S series.
    It does the other way round, fails for good chips.
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    George I dropped you a private message. In case...

    George I dropped you a private message. In case you are registered for the notifications here.
  4. Power supply in my PC40-01 broke and I could not...

    Power supply in my PC40-01 broke and I could not find any information about it, so I ordered all semiconductors on the board and attempted replacing one by one. Eventually replacing the bridge...
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    You are absolutely amazing. I will contact you...

    You are absolutely amazing. I will contact you offline when my chips arrive. Of course I want to refund all the costs to you no question about it. Thanks a lot.
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    I managed to find the images:...

    I managed to find the images: http://bitsavers.org/pdf/apple/apple_III/firmware/
    And I managed to identify the compatible PROM chips:
    TS 82S137, 6353-1, TBP24S41, HM7643-5, 29641, 27S33, 74S573,...
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    How do you deal with broken PROMs?

    I am in need for Apple III PROM 342-0061 at motherboard location C11.
    Does anyone have spare to sell?
    Is it possible to burn in a new prom assuming I could get unused parts? I could not find PROM...
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    I confirm. These cheap low powered testers do not...

    I confirm. These cheap low powered testers do not test S chips correctly. But F chips get tested ok. Great advice, Thanks.
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    Apple III video problems

    Hi,
    I am fixing my Apple III machine. The first symptoms are that it does not show anything on the screen.
    Apart from that, it is possible to ctrl-reset it, it will kick off the FDD, or to...
  10. Sinclair Amstrad APC 386 SX / Amstrad 3386 SX - help!

    Hi,

    I have a Sinclair Amstrad APC 386 SX, also known as Amstrad 3386 SX, complete main unit with original 40MB Seagate HDD.
    There is practically zero documentation on the web of this machine....
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    Funny thing, I am testing my Apple III chips and...

    Funny thing, I am testing my Apple III chips and found the same.
    Two 74S257 on board and one 74S158 on RAM card are reported faulty by TL866.
    But some other S like 74S153 pass. None of the LS are...
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    Well, I think we don't know that for sure and are...

    Well, I think we don't know that for sure and are figuring it out. What would be connected to the RCA on the other end to read the serial data?
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    I think the drawings show all situations that...

    I think the drawings show all situations that qualify as a move in a direction. A full cycle as shown will generate a value of 4 or -4 - as there are 4 edges.
    OK, it is possible that the signals...
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    And the whole code with comments for reference: ...

    And the whole code with comments for reference:



    ORG 00007H

    ; disable external interrupt
    DIS I ; 0007
    ; disable timer/counter interrupt
    DIS TCNTI ; 0008
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    P1.4/5 and P1.6/7 are used to detect a direction...

    P1.4/5 and P1.6/7 are used to detect a direction of move and have to look like that:


    Positive direction
    ______
    ____| |_____
    ______
    _______| |_____
    Negative direction...
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    Let the fun continue... I have looked through...

    Let the fun continue...
    I have looked through the beginning of the code and came to an interesting conclusion that P1.4 and P1.5 must be some signals that are expected to be phase synced - change at...
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    So here is a schematic of the board. Now you can...

    So here is a schematic of the board. Now you can see how RCA and DB9 are connected.
    49052

    Combining this with the ROM listing, it should lead somewhere, but I have no more time today.
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    This seems correct - the NEC Dx lines are...

    This seems correct - the NEC Dx lines are connected to ROM Dx outputs and at the same time to the 74373 8-bit latch inputs. The outputs of 74373 go to ROM address lines. Address is latched by NEC ALE...
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    Dump of ROM content: 49008 And the...

    Dump of ROM content:
    49008

    And the disassembly, it actually looks like making some sense, though I have not yet tried to analyse it:




    ORG 00007H
    DIS I ; 0007
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    I attached an oscilloscope and RCA has a...

    I attached an oscilloscope and
    RCA has a constant output of -5V, it does not change in time
    DB9 pins have +5V or 0 and they do not change in time too
    I suppose some of them are inputs and maybe...
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    Here you go. When I find some time I will dump...

    Here you go. When I find some time I will dump the ROM and see with oscilloscope what is at the RCA.
    It seems like MCS 48 type of microcontroller, we should be able to disassembly it or maybe even...
  22. Looking forward to it, thanks.

    Looking forward to it, thanks.
  23. There are pictures of the boards with separate...

    There are pictures of the boards with separate battery and they have mc146818p installed (e.g. https://www.flickr.com/photos/osr/8143542588).

    Exactly, I am looking for the pictures of the board in...
  24. Compaq Portable III - help needed with some parts identification

    Hi,
    I am restoring Compaq Portable III. It is a version with cmos battery integrated with the real time clock chip. This chip was missing on my board - probably battery leaked and someone removed...
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    Thanks for the answers and the link to the forum....

    Thanks for the answers and the link to the forum.
    This is definitely not monitor connector, there seems to be power on the CGA GND pin and plugging monitor causes immediately a short circuit.
    The...
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