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Thread: Apple IIe platinum will only operate as if shift is always being pressed.

  1. #1
    Join Date
    Jan 2012
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    Default Apple IIe platinum will only operate as if shift is always being pressed.

    I have a apple IIe platinum model A2S2128 which is doing something strange. No matter which keyboard I use on it, it only behaves as if the shift buttons are always being pressed. In other words I cant use the numbers on the top row of the keyboard as they only show symbols. And regardless of the capslock key position all keys are always in caps. I have tried 3 keyboards all behave the same. I even tried swapping out the keyboard rom 342-0132-D for another and that had no effect on it. Any ideas?

  2. #2
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    Well turns out it was a bad AY3600931 PRO IC (to the right of the Keyboard ROM). I pulled it from another board and tried it out. Immediately every key worked as normal. I cleaned the pins and used deoxit on the socket but couldn't get the original chip to work. Anyone know what the AY3600931 PRO IC is/does?

  3. #3

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    That's the keyboard scanner/encoder chip. It scans the keyboard, then outputs an address to the keyboard ROM, which then outputs an ascii value to the keyboard memory location.

    The shift key isn't scanned the way most of the rest of the keyboard is (as the way the 3600pro is set up in the apple 2, it has no rollover and can only detect one keypress at a time). I can't remember off the top of my head exactly how it's wired up, but IIRC it essentially acts as an extra address line to the keyboard ROM. But if replacing the chip fixes the problem, then I guess we are pretty sure that the old one is bad. XD

    The 3600pro came from the factory in a variety of configurations, and was used in several old 8-bit computers. If you buy a replacement, make sure it's the Apple 2 version, or you may have trouble. I know the Apple 2 uses one special function on the optional pins that could be configured at the factory, but I don't remember off the top of my head what it is.

    I have a copy of the datasheet for that chip around here somewhere, if you want it. I don't think it'll tell you anything you don't already know, though.
    -- Lee

    May Be Interested In Acquiring: Mac IIsi, Quadra 840AV, Commodore PC(286+)/64C/128D, PC-era Tandy stuff, Peculiar Old Serial Terminals.
    Old Computer Fun! (Muh Projects Blahg) | Muh YouTube Channel that goes with it

  4. #4

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    Also, I think the Plat //e is the only one that had the "shift key mod" done at the factory. It causes pressing shift to also activate one of the buttons on the game port, so software can tell when the shift key is pressed (on previous models of //, this was impossible without this mod being done). The side effect (if I recall correctly) is that if you press shift while also pressing the first button on a second joystick (button 2), it'll crash the machine.

    If I am recalling correctly. I may be more or less full of poo if I'm not. =:3
    -- Lee

    May Be Interested In Acquiring: Mac IIsi, Quadra 840AV, Commodore PC(286+)/64C/128D, PC-era Tandy stuff, Peculiar Old Serial Terminals.
    Old Computer Fun! (Muh Projects Blahg) | Muh YouTube Channel that goes with it

  5. #5
    Join Date
    Jan 2012
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    Connecticut, USA
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    I cleaned the pins and sockets on the faulty chip and tried it several times. It would always just display uppercase and none of the primary number buttons (only symbols) So I'm very certain its faulty. I will keep an eye out for an apple II version if I replace it. For now since the chip isnt completely dead I just put it in a spare board and labeled it.

    Funny thing, I thought it was the keyboard originally as their was a bodge wire on one of the pins of the left shift switch running all the way back to the keyboard ribbon header with a couple dabs of silicone to keep it in place. Never saw that before so I was unsure it was factory or not. I tried de-soldering the wire to see if it made a difference, but it didn't. Again I tried a couple other keyboards and they displayed the same issues. I just re-soldered that wire and left it as is now that its working again. Id send a photo but I already put the unit back together.

  6. #6

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    How are you progressing with this machine?
    -- Lee

    May Be Interested In Acquiring: Mac IIsi, Quadra 840AV, Commodore PC(286+)/64C/128D, PC-era Tandy stuff, Peculiar Old Serial Terminals.
    Old Computer Fun! (Muh Projects Blahg) | Muh YouTube Channel that goes with it

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