Image Map Image Map

Search:

Type: Posts; User: Dwight Elvey

Page 1 of 20 1 2 3 4

Search: Search took 0.10 seconds.

  1. I was wondering how you'd kill a 74145 with a...

    I was wondering how you'd kill a 74145 with a probe? You'd have to hit one of the outputs with +5 or +12 or something.
    Dwight
  2. Replies
    3
    Views
    129

    Not port 2 bit, mask value 02H. Both bit mask on...

    Not port 2 bit, mask value 02H.
    Both bit mask on port 1. You asked for the mask, not the port.

    see:
    http://bitsavers.org/components/gi/_dataBooks/1977_GI_Data_Catalog.pdf
    page 8A-3
    pin 19
    ...
  3. Don't put switches in the dish washer. Dwight

    Don't put switches in the dish washer.
    Dwight
  4. No, I have to give it more thought. I'm not able...

    No, I have to give it more thought. I'm not able to view the video you have.
    Dwight
  5. The electrolyte used in capacitors is a base. Use...

    The electrolyte used in capacitors is a base. Use white vinegar and then rinse with water, followed by DI water rinse.
    Dwight
  6. Replies
    3
    Views
    129

    From the manual, page 4 Status Port, Transmiter...

    From the manual, page 4 Status Port, Transmiter Empty is bit 0 and Data Available is bit 1 of the SWEA port. RX rdy would be 02H and TX rdy would be 01H. There are several error bits that one might...
  7. 20 and 17 has a feed through, connecting them...

    20 and 17 has a feed through, connecting them together. For the IMSAI, they shouldn't be connected together.
    Dwight
  8. I was just rereading my post. I should have said...

    I was just rereading my post. I should have said common return wire from the bus, rather than ground. Many think of ground as being the metal chassis and often the power return is connected to the...
  9. First thing to do is to check the power rails to...

    First thing to do is to check the power rails to ground with the ohm meter. For the + rails put the black lead on ground. For the negative lead put the red lead on ground. The meter should jump to...
  10. I'll get back to you. In the middle of stuff....

    I'll get back to you. In the middle of stuff.
    Dwight
  11. Replies
    423
    Views
    8,825

    Looks good to me. Dwight

    Looks good to me.
    Dwight
  12. Try some cold spray on the video RAM. If you have...

    Try some cold spray on the video RAM. If you have none, I've use isopropyl alcohol and a fan. It will likely show as a thermal issue.
    Dwight
  13. On my chromebook it looks like a 'm' but on a 21...

    On my chromebook it looks like a 'm' but on a 21 inch screen it looks like an 'n'.
    It looks like a typical under sampled shot but maybe it was just having troubles syncing. Anytime your looking at...
  14. When you see this kind of signal on a digital...

    When you see this kind of signal on a digital scope, look at the sweep rate. If you are using a auto sweep detect, turn it off and set the rate to an appropriate sweep for the frequency you intend to...
  15. Most 1X probe are can be around 60 pf. Hitting a...

    Most 1X probe are can be around 60 pf. Hitting a 8 MHz line is like slapping it with a 330 ohm resistor. Also remember that a square wave is composed of harmonics. The impedance for them is smaller...
  16. I do wish you guys would learn how to use a...

    I do wish you guys would learn how to use a digital sampling scope. The trash you see on the screen is under sampling a high frequency signal. You can't look at a 8 MHz signal with a 100 Ms/div...
  17. Replies
    17
    Views
    339

    Ops I meant T13. This is the regulation feedback...

    Ops I meant T13. This is the regulation feedback to the primary side of the switcher. T21 and T22 form a oscillator with the primary coil. It T13 is turned on it would stop the oscillation. T20 could...
  18. Removing pin 20 was OK ( my error ). Follow the...

    Removing pin 20 was OK ( my error ).
    Follow the following, remove these and leave them out, in sequence. Test after removing each chip.

    I assume when you said that you remove the buffer, you...
  19. You really should use tape. There was no reason...

    You really should use tape.
    There was no reason to cut 99? Also 20 is your only ground??
    Please don't cut any more traces.
    Please this time, list what actions you did , what it actually did?
    I...
  20. Replies
    17
    Views
    339

    Any electrolytic capacitor showing corrosion is a...

    Any electrolytic capacitor showing corrosion is a throw away.
    What is the voltage at T3 base?
    Dwight
  21. I didn't think of that, thanks for reminding me....

    I didn't think of that, thanks for reminding me. More tape to mask pins. I would think the thin packaging tape would work well. You want it to be thin so as to not bend the socket pins.
    70 and 98...
  22. Looking at the interfacer 1 manual, I don't see...

    Looking at the interfacer 1 manual, I don't see anything that should be an issue. The only driven signals onto the bus are the data lines and the interrupts.
    Dwight
  23. I believe you had DRAM. What kind of DRAM board...

    I believe you had DRAM. What kind of DRAM board do you have. Many don't do real refresh, controlled by the CPU. Things like interrupts from the serial card can cause the DRAM to stop refreshing. You...
  24. I should note why using an ohm meter to locate a...

    I should note why using an ohm meter to locate a short is usually useless.
    First the short is usually less than an ohm. Lets say it is 200 mlliohms. The traces supplying the power rail are usually...
  25. Generally most supplies that we have don't have...

    Generally most supplies that we have don't have over current protection on the outputs, other than a input fuse. Also the only place I saw any kind of reverse voltage protection was on my lowly...
Results 1 to 25 of 500
Page 1 of 20 1 2 3 4