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Thread: KIM-1 memory issues?

  1. #11
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    Quote Originally Posted by snuci View Post
    I am a bit confused if memory at U9 is bad or everything else is bad BUT U9.
    I took a shot at it being one bad RAM and presto, fully working KIM-1! I do have one segment display not lighting up but I can replace that later.

    It's really good to know you can't get past the memory test/repair before checking the other items. I was worried that it was in REALLY bad shape. This one is not i the greatest conditon and went through some hard labor in it's lifetime.

    Now I have one more that doesn't power up (Rev E). When I press RESET the Access light goes out. I'll try to figure that one out myself first.

    Thanks again Dwight!

  2. #12

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    Quote Originally Posted by snuci View Post
    Hi Dwight.

    I found a missing trace! It was between pin1 of U4 and pin 1 of U16. I couldn't see it until I desoldered the 7404 and replaced it and noticed some discoloration where the trace used to be.I checked against another KIM-1 and sure enough, it was missing. The memory test now displays 2 long, 1 short, 4 long.

    I am a bit confused if memory at U9 is bad or everything else is bad BUT U9.

    DBINSTR.TXT says short is bad as noted, "A 1 second blink indicates a good bit and a short blink indicates a failed bit."
    RAMTEST.SEQ says short is good as noted, "A short blink means that bit is good. A long blink indicated that bit bad. The long blink is about 1 second. The short one is clearly short."

    One of them is right and I am inclined to think that RAMTEST.SEQ is right if it's the code.

    Can you clarify? I did the display test and it failed the first time but then worked a second time so we are getting somewhere, I think.
    I believe the TXT file is correct. I recall checking it several times to make sure I got it right in the instructions. The text in the SEQ file is just a comment. It is more likely to be wrong. It may have been the original intention but, when looking at the result, I'd changed the code without fixing the comment. At least that is my guess.
    You can short the Dout of U7 to ground and see what it does. You should see it fail two instead of just one. Use care to not use +5V instead of ground or you'll be fixing 2 RAMs.
    It is possible that they cut the trace to use a larger off board RAM. The fact that it is failing a RAM bit now may have been just that the part is old. The 2102s were always failing.
    Dwight

  3. #13

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    Your total blinks are 7 instead of 8. Could you have missed one?
    Dwight

  4. #14
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    Quote Originally Posted by Dwight Elvey View Post
    Your total blinks are 7 instead of 8. Could you have missed one?
    Dwight
    You are right. I missed entering one in my description. Two long, one short, five long for a total of 8.

    One question. What switches should I set to bypass the debug board and just use it for power only? While I have it connected, I use it for just normal power.

  5. #15

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    I think it is stated in the documents but I forget? It still has K3 decode the EPROM on the debug board. That is always hard wired. There should be a note two places that you can run a couple games. With these you boot the KIM's monitor and enter the address of the game located on the debug board EPROM. These do not boot to the debug board so in a sense, these are what you want. It is just that the debug board is still wired to K3 that is unused in the memory map any way. From one of these, you can run anything that would normally run on a KIM-1 or even load from a cassette.
    Dwight

  6. #16

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    Quote Originally Posted by snuci View Post
    I took a shot at it being one bad RAM and presto, fully working KIM-1! I do have one segment display not lighting up but I can replace that later.

    It's really good to know you can't get past the memory test/repair before checking the other items. I was worried that it was in REALLY bad shape. This one is not i the greatest conditon and went through some hard labor in it's lifetime.

    Now I have one more that doesn't power up (Rev E). When I press RESET the Access light goes out. I'll try to figure that one out myself first.

    Thanks again Dwight!
    It is either the CPU has failed, it is getting a constant interrupt or something is loading an address or data line.
    Good hunting.
    Dwight

  7. #17
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    Thanks for the posts. Seems kind of simple now that you point out how to run the KIM-1 normally with the debug board. I should have put 2 + 2 together.

    As for the bad KIM-1, I tried replacing the CPU already. No luck. I'll keep at it. I do have a scope so I may have to break that out and compare a working KIM-1 against the bad one.

  8. #18

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    Quote Originally Posted by snuci View Post
    Thanks for the posts. Seems kind of simple now that you point out how to run the KIM-1 normally with the debug board. I should have put 2 + 2 together.

    As for the bad KIM-1, I tried replacing the CPU already. No luck. I'll keep at it. I do have a scope so I may have to break that out and compare a working KIM-1 against the bad one.
    Don't forget to check for a clock. Just run around the pins on the cpu and look for something unusual.
    Dwight

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