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  1. @Corey: Also, do you happen to recall which...

    @Corey:

    Also, do you happen to recall which paint you used?

    Thanks,

    Dave
  2. Corey, I'm interested in reproducing the paper...

    Corey,

    I'm interested in reproducing the paper badge as well. Did you print this yourself, or did you have a service print it?

    Dave
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    For anyone interested, I've added the design...

    For anyone interested, I've added the design files to github:

    https://github.com/osiweb/Hardware/tree/master/new/sol20/sides

    Dave
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    Ah, yes, I can see the spot weld marks. But...

    Ah, yes, I can see the spot weld marks. But since the parts are painted, spot welding them back together is not an option, even if I had a spot-welder. I think the best bet is to epoxy them...
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    I installed the threaded inserts today. ...

    I installed the threaded inserts today. Unfortunately, I installed the upper insert for the right panel in the wrong position, so I have to take it back to the Makerspace (to use the drill press)...
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    Of course, anybody who randomly probes without...

    Of course, anybody who randomly probes without thinking gets nowhere. But that person still needs to learn when and how to use the tool.

    Definitely, there is no substitute for thinking about the...
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    The high bit determines the color group, so a...

    The high bit determines the color group, so a stuck bit could produce the symptom, under some circumstances. A faulty bit could be a bad RAM chip, but also a faulty register.

    Dave
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    And to answer more literally, where to connect...

    And to answer more literally, where to connect the probe depends on the board. Sometimes there are convenient test points In many cases, you will probe a ship or discrete device directly holding...
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    It's a good question. To a beginner, the options...

    It's a good question. To a beginner, the options seem limitless. A scope only has two or four traces, and they should be meaningful. Hobby time is limited. You must be judicious.

    The key, not...
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    Since it began working after just removing and...

    Since it began working after just removing and replacing the chip, you are right that it's probably a socket issue. I was only speculating on the cause of the color issue, since the problem seemed...
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    That looks like part of the video/DRAM timing...

    That looks like part of the video/DRAM timing generator circuit. Most failures here would result in all-or-none failure modes. The section does output a color burst enable signal. Perhaps the...
  12. Thread: My first Rev 0!

    by dfnr2
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    If you have access to a large enough ultrasonic...

    If you have access to a large enough ultrasonic cleaner, you can consider dunking the whole keyboard in the bath, or if you have a smaller one, try suspending the keyboard vertically by a wire (or...
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    You're not generating blue/orange. Looking at...

    You're not generating blue/orange. Looking at the schematic, there's a shift register (A11) that produces a 1 clock-cycle delay to turn green/magenta into cyan/orange.

    If A11 failed, most likely...
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    Actually, I spoke too soon. There is a...

    Actually, I spoke too soon. There is a difference between A85 and the CP/M 8080 assembler. The CP/M assembler maps a string "AB" to memory in order, with 41h at the low byte and 42h at the high...
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    Almost done.

    Almost done. Here are the replacement panels next to the originals (new panels in the center):

    56477

    I just need to install the threaded inserts.

    56476

    I tried to use a screwdriver to...
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    Testing the sides for fit: 56473 56475 ...

    Testing the sides for fit:

    56473 56475

    There's some parallax due to the camera, but the fit is nearly perfect.
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    That's an interesting tidbit, and makes sense. ...

    That's an interesting tidbit, and makes sense. Come to think of it, the OSI systems also use Shift-O to delete a character, by placing an underscore (0x5f) in the buffer. For each underscore, the...
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    That works perfectly. Compiles with a few minor...

    That works perfectly. Compiles with a few minor warnings with GCC on MacOS. Thanks!

    Dave
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    That's what I'm doing now, and it works. ...

    That's what I'm doing now, and it works. However, putting that in a makefile would require a lot more prerequisites and a lot more complexity to do a build compared with requiring a single...
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    CP/M compatible cross assembler?

    Does anyone know of a cross assembler for the 8080 that can compile CP/M format assembly files? I am trying to compile various Personality Module images for the SOL-20 from CP/M assembly source. It...
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    Thanks for that info. I believe that Rubout on...

    Thanks for that info. I believe that Rubout on most keyboards generates a DEL character. I wasn't aware of a separate Rubout code.
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    Good to know, thanks!

    Good to know, thanks!
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    I got the replacement 4051 and finally, all the...

    I got the replacement 4051 and finally, all the keys are functioning. However, I did notice an oddity:

    SHIFT+DEL doesn't produce an underscore character, but rather acts just like DEL. Given...
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    Thanks! Nice! That sounds like a great idea.

    Thanks!

    Nice!

    That sounds like a great idea.
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    Well, it was not too complicated. Starting at...

    Well, it was not too complicated. Starting at the "O" key, number 27, there were pulses at the pulse pad, and there was continuity to the 4051. From the schematic, the "O" key is on the same row as...
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