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Thread: 5150 16k-64k Keyboard not working?

  1. #1
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    Default 5150 16k-64k Keyboard not working?

    Keyboard just quit working, it has been working.

    I have three IBM F keyboards and none work with this unit.

    Anyone have a starting point.

    Thanks

    framer

  2. #2
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    Quote Originally Posted by framer View Post
    Keyboard just quit working, it has been working.
    Confirm for us that you are seeing a 301 error at power-on time.

    Quote Originally Posted by framer View Post
    I have three IBM F keyboards and none work with this unit.
    So, the IBM 83-key keyboard, as shown at [here].

    Quote Originally Posted by framer View Post
    Anyone have a starting point.
    See the 301 error description at [here].

  3. #3
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    No 301 error shown.

    Yes, real IBM 83 key keyboard

    Boot to OS without issue but keyboard does not work.

    Tried DOS 1.1 3.2 6.22 CPM 1.0

    All boot but no keyboard input.

    Thanks

  4. #4
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    I even tried the original Diagnostics disk 1502367 Loaded fine but because keyboard does not work I'm unable to run diagnostics on the system board.

    I've also unplugged all cables and cards and reattached with no joy.

    Bizarre this is...

    framer

  5. #5
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    Maybe one more clue "I get no beep before the system loads.", just silence.
    Yes, there is a speaker attached.

    framer

  6. #6
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    I found the maintenance manual 6280087 worked the MAP and on page 0300-4 019 checked the voltage shown for the pins on the keyboard connector. Pin 1 was suppose to have +2.0v to +5.5V I shows .1mV or 0 Manuals recommends I replace the system board. Well that's just great. Board only lasted 39 years. FYI all other pins checked OK on voltage.

    framer

  7. #7
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    Fortunately, the keyboard "controller" on the 5150 is very, very simple--mostly just a shift register. (See the schematic) using commodity parts. Should be a simple repair. Also, check from broken traces around the motherboard DIN connector--sometimes these get wrenched loose and you lose continuity.

  8. #8

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    If you say "also no sound" and clock pin with no signal, that points to a 8284 (U11) clock generator failure (that generates peripheral clock PCLK signal) or maybe 8255 peripheral controller (U36) because both things depend on that. Maybe a broken trace or something shorting pin 2 of the 8284. That should always output a 2.385MHz clock, and goes to pin 9 of U26, is divided by two and goes to pin 9 of 8253 (U34) for the sound and pin 3 of U82 for the keyboard. I would check all that signals and components.

  9. #9
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    Quote Originally Posted by framer View Post
    I found the maintenance manual 6280087 worked the MAP and on page 0300-4 019 checked the voltage shown for the pins on the keyboard connector. Pin 1 was suppose to have +2.0v to +5.5V I shows .1mV or 0 Manuals recommends I replace the system board. Well that's just great. Board only lasted 39 years. FYI all other pins checked OK on voltage.
    Pin 1 is the CLOCK line. It normally sits at a HIGH level. The MAP indicates that the measurement is to be done with no keyboard attached, and I presume you obeyed that instruction.

    On an IBM 5160, grounding the CLOCK line instructs the POST to go into a 'MANUFACTURING TEST' mode, a mode where no 301 test is done. Quickly looking at the source code for the IBM 5150's POST, I see similar. I think your POST is going into 'MANUFACTURING TEST' mode because the CLOCK line is LOW (or somehow grounded).

  10. #10
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    I was wrong in my previous POST. In the IBM 5160, grounding the DATA line, not the CLOCK line, is a method of getting the POST to go into MANUFACTURING TEST mode.

    I brought out a known-good 5150 motherboard of type 16KB-64KB, one fitted with the final BIOS revision, revision 10/27/82. Keyboard attached. No 301 error. Booted to BASIC where my keystrokes registered on-screen. Powered off. I then removed the keyboard then I grounded the DATA line and then I powered the motherboard on. No expected 301 error and then I soon heard a never-ending series of beeps. Looking at the source code for the 10/27/82 BIOS, the behaviour appears to match the MANUFACTURING TEST mode (skip keyboard test, skip ..., run the POST in a loop).

    Out of curiosity, I grounded the CLOCK line instead of the DATA line, and I observed the same behaviour.

    I put in the 04/24/81 revision BIOS. Grounding the DATA line, I saw the cursor appear, no 301 error, and then after a long minute of a flashing cursor, the never-ending series of beeps started.

    But there is beeping, and the POST appears to be running in a continuous loop. And I realised that your, "No 301 error shown", was not conditional, i.e. maybe you do see a 301 if the keyboard is removed. So the MANUFACTURING TEST mode hypothesis is gone.

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