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Type: Posts; User: Dwight Elvey

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  1. It is like a disease. One person makes it work by...

    It is like a disease. One person makes it work by replacing a bunch of capacitors and it spreads to maybe 10 or 20 others.
    None of them, including the original one have no idea how to trouble...
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    It is clearly the keyboard. One wonders why they...

    It is clearly the keyboard. One wonders why they brought so many pins out. It may have been a combination keyboard and monitor data. I can't quite make out the letters on the chips to the right but I...
  3. The NC4000 implementation of CMForth would of...

    The NC4000 implementation of CMForth would of course need low level fixes for the RTX2000 parts. I don't think all of the bit fields are the same. Most of the operations are the same though.
    Dwight
  4. Once done replacing the capacitors, you'd need to...

    Once done replacing the capacitors, you'd need to actually trouble shoot the power supply. It is clearly a good idea to replace the RIFA anyway. As always, I'd recommend finding out what failed first...
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    I have to get back to working on the disk...

    I have to get back to working on the disk controller of my Nicolet. There is a board in it that has a several IC's that are flops, as I recall. Some don't have pullup resistors but are just floating....
  6. A rare one to look for would be the KTM-2/80....

    A rare one to look for would be the KTM-2/80. These were made by Synertek. They are typically an open PC board with keyboard attached. They require a standard B/W video 60Hz monitor and power supply....
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    It might be a SYM-1 or even a SYM-2 as well. The...

    It might be a SYM-1 or even a SYM-2 as well. The SYM-2 is small enough to fit into the space. The SYM-1 is a little large.
    Dwight
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    I have a rare Polymorphic keyboard with the same...

    I have a rare Polymorphic keyboard with the same affliction. If it is only one corner busted, careful snipping can remove part of the broken corner but the other corners are easily broken. Someone...
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    I don't think it was a keyboard. It was more...

    I don't think it was a keyboard. It was more likely a single board computer stuffed in a large generic keyboard case. Maybe a Commodore or similar.
    Dwight
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    I really depends on the length between drivers...

    I really depends on the length between drivers and receivers. Technically it is a transmission line problem. Still, in most cases, it is just replacing the typical pull up of the the circuit designed...
  11. To bad, it was looking like an interesting...

    To bad, it was looking like an interesting problem.
    Dwight
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    I enjoyed the hunt. Here and at work, I always...

    I enjoyed the hunt.
    Here and at work, I always try to clearly convey my thoughts, in a clear way. It is difficult but I am learning as well. As I'm getting closer to retiring, my boss wants me to...
  13. Another possible problem is the voltage swing of...

    Another possible problem is the voltage swing of the tach. If it is weak, the motor will run faster because there will be less voltage to drive the amplifiers. I'm not sure what they used for a tach....
  14. Few fuses would blow fast enough to save diodes...

    Few fuses would blow fast enough to save diodes from a hard short.
    Dwight
  15. I'm more of an analog guy. Humor me and make the...

    I'm more of an analog guy. Humor me and make the measurement.
    Also, the high side of the pot adjustment looks wrong. It should be over 5 Volts. I suspect the adjuster is broken inside. The...
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    I was working for a company called speed call (...

    I was working for a company called speed call ( before some reading this were born ) and we made touchtone decoders for taxi cabs ( and cement trucks ). I was probing one board for some failure when...
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    For unused inputs, I typically use 5K( actually...

    For unused inputs, I typically use 5K( actually 4.7K ) or 10K. The reason for using a higher value is that if there is a high load on an output, you don't want the input pin driving the power rail....
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    If I recall correctly, the wire was related to...

    If I recall correctly, the wire was related to blocking the read of the video RAM while the external board video board RAM was attached.
    It sounds like you might need some soldering lessons. You...
  19. Measure the voltage between pin 4 and pin 10 on...

    Measure the voltage between pin 4 and pin 10 on the 2917. It should be close to 0 volts and stay close to the same voltage when light changes in load.
    It should stay near zero as you run the pot...
  20. One of my pages above has examples of simple and...

    One of my pages above has examples of simple and more complete system at the schematic level.
    Dwight
  21. There is quite a bit of RTX2000 stuff on the web:...

    There is quite a bit of RTX2000 stuff on the web:
    http://users.ece.cmu.edu/~koopman/forth/RTX_Training_slides.pdf
    http://netwinder.oregonstate.edu/devteam/andrewm/forth/strongarm/docs/rtx2010.pdf...
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    I get a lot of site not found errors. It is...

    I get a lot of site not found errors. It is frustrating when you've type a lot of stuff and forget to first do a copy of the text before trying to post.
    If I copy it first, I can always try several...
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    If the winds are not tight against each other, it...

    If the winds are not tight against each other, it has to be redone. I've seen people wrap a little loose and push them together. That doesn't work. It is either right or remove it and use fresh wire....
  24. I wish I could find the page that a student at...

    I wish I could find the page that a student at one of the universities was looking at a stack processor and how efficient it was. Compared to an highly optimized RISC or CISC processor, a stack...
  25. This is also a good reason to know what bits make...

    This is also a good reason to know what bits make which patterns on the video out.
    The data in the video ROM should be a regular part of the debug.
    Dwight
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