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Type: Posts; User: Dwight Elvey

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  1. That is random stuff in the video RAM when it...

    That is random stuff in the video RAM when it starts. It looks like it is doing the proper initialization of the screen but not bringing up the signon prompt. This would indicate that the problem is...
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    Once the video RAMs are off, one can easily check...

    Once the video RAMs are off, one can easily check with a few scraps of wire. I agree, it looks like the video ROM but it also looks a little like the processors instruction data being displayed as...
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    The one he had is: ...

    The one he had is:

    http://kripton2035.free.fr/Resources/HP%20547A%20Current%20Tracer%20Manual.pdf

    HP also made another one that used contacts to measure current through a pin. I recall using...
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    Wow, the guy has a HP current probe. Not every...

    Wow, the guy has a HP current probe. Not every one is that lucky.
    Dwight
  5. There are a number of 3 line display phones on...

    There are a number of 3 line display phones on ebay but I don't think they are a long as you're after.
    Dwight
  6. If it is a LCD with the driver board attached,...

    If it is a LCD with the driver board attached, you stand a chance but if the main board has the LCD controller on it, it may be more difficult. Most of those on separate driver boards were bought as...
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    If the video RAMs are on sockets, you can create...

    If the video RAMs are on sockets, you can create your own characters with jumper wires to ground and maybe some pullup resistors ( 10K are fine ).
    That will help you separate what side the problem...
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    The value of a VX81 is much more than a 2114....

    The value of a VX81 is much more than a 2114.
    Dwight
  9. Years ago when I did a FPGA course, I did a 16...

    Years ago when I did a FPGA course, I did a 16 register stack cashing. We never got it to work because of timing issues with the Forth engine design I started with.
    As I recall, one of the...
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    Hi Fran We've shown that SA4 gets to the RAMs...

    Hi Fran
    We've shown that SA4 gets to the RAMs correctly, yet the display is messed up for SA4. On your original test we could also see a + sign making it back but being inverted. I suspect these...
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    You'd think they'd keyed them to keep us idiots...

    You'd think they'd keyed them to keep us idiots from getting it wrong.
    Dwight
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    Parts in the 6500 family are usually quite OK to...

    Parts in the 6500 family are usually quite OK to stick in backwards. Unlike other parts their power supply is all on one side instead of on diagonal corners.
    I put a TI EPROM in backwards once. It...
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    Just more exploration to go through. I would...

    Just more exploration to go through. I would assume you program produced a tone for the morse coded signal.
    Although, I'm sure the board is quite clever, it probably requires to be set to receive a...
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    Hi Dave I'm not sure but the with my...

    Hi Dave
    I'm not sure but the with my understanding of your test, the video Fran poster in #70 would indicate that your test is seeing a bad video RAM. Is that right?
    Dwight
  15. It depends on what it is for. Many lap top...

    It depends on what it is for. Many lap top manufactures use the same screen bought from the same manufacture. You didn't think Dell makes LCD screens do you. I have an old Dell that I got from a...
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    Too many Daves in the world. Don't get me started...

    Too many Daves in the world. Don't get me started on Bobs.
    Dwight
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    Plugged a 486 in the wrong way. Dwight

    Plugged a 486 in the wrong way.
    Dwight
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    It should still work. All that board does is...

    It should still work. All that board does is substitute, selctively, the RAM or ROM as seen by the processor.
    Dwight
  19. Agree The magic is gone. Dwight

    Agree
    The magic is gone.
    Dwight
  20. I believe there are several ( at least two )...

    I believe there are several ( at least two ) stack processor FPGA designs on Github. At $250 for a RTX2000, that is a bargain. The space ready parts are much more than that. I have a setup with a...
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    I suspect the problem is inside of the RAM for...

    I suspect the problem is inside of the RAM for the addressing as well and data. We can see that the counter is getting through the mux for both high and low for SA4. Although, we've not tested for...
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    If I'd realized that the video RAM wasn't tested,...

    If I'd realized that the video RAM wasn't tested, I'd have looked at the screen a little closer and how it failed. We'd still have scoped the SA4 some but not spent as much time looking at good...
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    It might be better to follow this thread for some...

    It might be better to follow this thread for some time and then make a new post. You'll get better response and the people helping won't confuse the two similar threads.
    There are a lot of things...
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    Ok, I went back to the first post. On the first...

    Ok, I went back to the first post. On the first post, it was stated that all the RAM was tested good. I'm not that sure that the video RAM was included on that test. Looking at the web page...
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    Yes but once located, a simple jumper wire can...

    Yes but once located, a simple jumper wire can correct it.
    I'm suspecting that the trace was damaged while unsoldering RAM and installing sockets. If the wire is good then we may have a more serious...
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