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Type: Posts; User: Dwight Elvey

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  1. Replies
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    Just make a 555 oscillator. It doesn't need to be...

    Just make a 555 oscillator. It doesn't need to be particularly high speed. It is just to make proof of concept. Maybe 100KHz for a starter. Loop the Rx and TX, as well as any line controls needed for...
  2. Dish soap is intended to loosen organics and it...

    Dish soap is intended to loosen organics and it most likely the best for mouse poo. As glitch says, remove or be willing to replace pot and dip switches.
    Dwight
  3. Your's is the same, just some of the wires are...

    Your's is the same, just some of the wires are different colors and someone added an extra capacitor to the 8V, on his.
    Dwight
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    Now it is making a little sense. It is intended...

    Now it is making a little sense. It is intended that the remote machine echos to the part that does the video. What you'd call full duplex. You need to make a loop back to see what is being typed,...
  5. With no load, you should be able to see the...

    With no load, you should be able to see the output voltage stabilize with even a 100uf capacitor. If the voltage comes up and stabilizes right away, the large caps are dry. If there is another...
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    ST-506 is only 5 Meg. What level of DOS will you...

    ST-506 is only 5 Meg. What level of DOS will you be using. It has to be one of the original levels as later ones require 10 Meg as a minimum.
    Dwight
  7. Some of the solder joints look bad. For 9V DC...

    Some of the solder joints look bad.
    For 9V DC with a two diode full wave rectification the AC rms voltage would be 6.8VAC.
    The two diode setup would use a center tapped transformer. I doubt the 18V...
  8. I'm not too happy about 6.5V and 30 seconds....

    I'm not too happy about 6.5V and 30 seconds. Unloaded, the 8V line should be more like 9V. There is a high resistance in series with the rectifiers that shouldn't be there or the capacitors are empty...
  9. Once you've stepped the capacitor voltages up to...

    Once you've stepped the capacitor voltages up to about 2V, I've not had issues bringing them all the way up.
    Do check the capacitor polarities with the meter. The machine has been through a lot.
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    Most of the code for the CP/M-68K was written in...

    Most of the code for the CP/M-68K was written in C. The Z8000 CP/M was basically copied from the 68K CP/M. I believe Gaby has source for many of the ustilities, like editor, library tools and basic...
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    The problem is the guide rail is held on with a...

    The problem is the guide rail is held on with a small piece of nylon at both ends. The front end doesn't seem to have an issue but the back piece is over stressed and 100 percent of the drives I've...
  12. I don't think it is the controller that is an...

    I don't think it is the controller that is an issue. It is the firmware on the EPROM. You can tell the controller to go to the extra cylinders. These are often used for parking the heads. Most bios...
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    The fact that the screen is stationary would...

    The fact that the screen is stationary would indicate that it is reading uninitialized data. I've not looked at the original schematic but it may not have had a clear of the RAM on power up. Try some...
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    They look really nice after 40 years. They look...

    They look really nice after 40 years. They look about as good a new. Useless though.
    Dwight
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    A useful 68000 deveopment machine

    I was looking at the earlier post on the development system with key pad and LED display. Although, these machines are fun to fiddle with and clearly collectable. If I were doing anything serious...
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    I have never seen a bumblebee cap that wasn't...

    I have never seen a bumblebee cap that wasn't leaky. I used to check every one I removed. 100% failure!
    I have some waxed paper caps made in the late 40's that tested fine.
    As was noted in the...
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    The spec says 10 ua but that is under mornal...

    The spec says 10 ua but that is under mornal operating voltage. It may be without VCC, it draws more.
    Dwight
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    The VB had sprites but the Channel F didn't. This...

    The VB had sprites but the Channel F didn't. This limited what the Channel F could do in real time as well as possible overlays. If I recall correctly the VB had collision detection for sprites as...
  19. You need to soak them. It takes time. It took...

    You need to soak them. It takes time. It took year to dry out it'll take some time. Soak them with water and dish soap.
    Dwight
  20. Good idea. Dwight

    Good idea.
    Dwight
  21. Yellow -18V Red +18V White +8V Dwight

    Yellow -18V
    Red +18V
    White +8V
    Dwight
  22. That is correct. When you power up, use your...

    That is correct.

    When you power up, use your voltmeter and measure on both of the small capacitors. You want to use the variac and bring the voltage to 0.5V and no higher. Make sure both are at...
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    I'd love to track it out and make a schematic. It...

    I'd love to track it out and make a schematic. It needs a different zif and cable to go to the 87xx part. From the schematic I should be able to determine what that would look like. I do have the...
  24. Look at photo ...

    Look at photo
    http://www.vcfed.org/forum/showthread.php?54047-IMSAI-8080-Questions/page3&highlight=power+supply
    post #21

    Even though the two capacitors have the positives post on the same side,...
  25. They are suppose to be rotated. The one on the...

    They are suppose to be rotated. The one on the right Is a POSITIVE rail It is suppose to have the black lead on the NEGATIVE side of the capacitor!!!!!!!!!!!!!!!!!!!!!!!
    The other is a NEGATIVE rail...
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