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Type: Posts; User: Dwight Elvey

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  1. I thought I'd update the retro stuff I've done....

    I thought I'd update the retro stuff I've done. I've use a 4004 emulator, that I wrote, to create a working piece of code written for the 4004 in 1973. It was printed on what I believe to be a ASR33...
  2. The most common problem on circuits that haven't...

    The most common problem on circuits that haven't suffered from static discharge is bonding wire failure. In this case, I don't think it was the bonding wire at least not the output wire. If it had...
  3. Yes, A1 counts the character rows. If I were...

    Yes, A1 counts the character rows.
    If I were just shot gunning I'd try B5 first but it could be C9, C5 or C6. Usually parts that fail are counters, then flops and then gates. They all fail at some...
  4. I should state that the display is exactly what I...

    I should state that the display is exactly what I might see if there was a fault in the horizontal counter. This also consistent with the occasional blank screen.
    The character counter and the C7...
  5. I need to explain the circuit to you. When the...

    I need to explain the circuit to you. When the horizontal does a retrace, it increments the row counter A1. It also reset the character counter. If the character counter never reaches a count of...
  6. I went back and looked at the way the display...

    I went back and looked at the way the display looked when it quit. It was not in horizontal sync when the vertical quit. The horizontal in the display is an oscillator that is resync'd to the...
  7. Another good parts supplier is Anchor...

    Another good parts supplier is Anchor Electronics. It is a good place for older TTL parts like the 7400 and the 74177. Look in their catalog at page 8:
    ...
  8. If your measurements of the E5 inputs and outputs...

    If your measurements of the E5 inputs and outputs where not a triggering error in the digital scope ( there are a lot of things I don't like about these scopes ), there are two possibilities for...
  9. As Hugo says, these are the worst types of...

    As Hugo says, these are the worst types of problems. When it fails, the vertical either stops or goes to a high frequency. The fact that, from one of your earlier pictures, there looked to be two...
  10. If the J input is held low and resets are not...

    If the J input is held low and resets are not activated the JK will not toggle.
    Please make the measurements I asked for. There is not likely anything wrong with C7. I can see that this has been...
  11. A brief description of the circuit. First the...

    A brief description of the circuit.

    First the display. Each character is composed of an 8X8 matrix of dots. Each line is 40 characters long and there are 1000 characters per screen.
    The...
  12. C8 pin 3 should be a pulse at 1 Mhz and ~64 ns...

    C8 pin 3 should be a pulse at 1 Mhz and ~64 ns wide.
    C6 pin 13 should pulse at about 16.6 ms. It is controlled by the character counters composed of E6, D6 and D7. The count is decoded by E5, E8 and...
  13. It is possible that it is the strobe polarity. ...

    It is possible that it is the strobe polarity.
    Dwight
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    Hal computer systems

    A friend has 2 Hal computer systems looking for a new home. One is a Beta machine and the other is a regular production. Both have been in storage for three years but both were running when put away....
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    I thought I might add this here. There are...

    I thought I might add this here. There are several simulators for the 4004 on the web. There is a mostly undocumented operation of the 4004 when you do a fourth JMS without a return. It over writes...
  16. I'm assuming you've jumpered the 5.25 right. Most...

    I'm assuming you've jumpered the 5.25 right. Most newer systems with 3.5s use twisted cables but the 5.25s have to be jumpered correctly work with a twisted cable. It is not the same as a straight...
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    A lot of these clock chips need to be started by...

    A lot of these clock chips need to be started by a write to some register. Look us the data sheet for your chip.

    Dwight
  18. Image centering is controlled by two small metal...

    Image centering is controlled by two small metal rings at the back of the yoke. Once you get the width and linearity the way you like from the controls on the board, you can then recenter using the...
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    I thought I'd post here as this may be a better...

    I thought I'd post here as this may be a better place to post than the Intel Library stuff.
    As I believe I mentioned, I'd gotten EPROMs with the labels A0740 to A0743. I'd believed that the 4th...
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    3870 stuff would be fun to use with the Video...

    3870 stuff would be fun to use with the Video Brain. It uses a external ROM for its code.
    Dwight
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    Made great progress today. I got the simulator to...

    Made great progress today. I got the simulator to run the two passes. It is not completely right. The first pass is suppose to output a number of 00h bytes. I've not figured what I can use to...
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    It seems Tom used a lot of corner cases. When I...

    It seems Tom used a lot of corner cases. When I was first looking at the code, I'd see case were the address of a JUN or JMS was the middle of a two byte instruction. He seems to like using this one....
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    Daver and I are making some progress. We've got...

    Daver and I are making some progress. We've got through the first part where it makes the first pass, picking up labels and adding marks for text to be ignored on the second pass. We,ve not exhausted...
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    I have no particular recommendations. The simple...

    I have no particular recommendations. The simple light with no wire cross connect is usually all that is needed but the ones with the jumper wires are handy when you don't want to solder up another...
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    Or, he can buy one of my punches. The only...

    Or, he can buy one of my punches. The only problem people have it that the punch gets dull and leaves a poor cut. The punch is made with drill stock but I don't know if it has been heat treated or...
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