Image Map Image Map

Search:

Type: Posts; User: Dwight Elvey

Page 1 of 20 1 2 3 4

Search: Search took 0.08 seconds.

  1. Replies
    4
    Views
    134

    The particular capacitor that blew is an RFI...

    The particular capacitor that blew is an RFI filter to the AC line. The power supply will run fine without it. The capacitors NEXT is talking about are the electrolytics. These often age and dry out....
  2. Replies
    82
    Views
    1,163

    I believe the code clears the screen by writing a...

    I believe the code clears the screen by writing a blank to each location. The video RAM is scanned by hardware and the CPU has little to do other than just updating the values. There is a mux system...
  3. Replies
    1
    Views
    78

    It looks like he fiddle with the pots as well....

    It looks like he fiddle with the pots as well. Mostly blind repairs.
    Dwight
  4. Replies
    82
    Views
    1,163

    You might as well remove that I8 chip. It is...

    You might as well remove that I8 chip. It is likely causing some issues.
    There seems to be some flakiness on things. I'd really like to see some scan with the NOP.
    Also, Daver, could you add a CRC...
  5. Replies
    82
    Views
    1,163

    I'd like to see some of the screen shots of G9,...

    I'd like to see some of the screen shots of G9, pins 15,14,13 and 12. ( G9 is the 74LS145 )
    These are the signals that should scan the keyboard. I believe we should trace down things we know are...
  6. Replies
    82
    Views
    1,163

    I'm not as concerned about the glitchy looking...

    I'm not as concerned about the glitchy looking spikes. These look like issues with the scope probes grounding. The scope probes ground must be near where the probe is measuring, as although the...
  7. Replies
    82
    Views
    1,163

    Can Dave or someone tell me which schematic I...

    Can Dave or someone tell me which schematic I should be looking at. I'd like to suggest a few things to look at?
    Dwight
  8. Replies
    82
    Views
    1,163

    Don't get discouraged. This is what trouble...

    Don't get discouraged. This is what trouble shooting is all about. You have a hypothesis as to what the problem might be and then you prove it either true or false. I need to go back through the...
  9. Replies
    8
    Views
    130

    Which machine did you format the drive on?...

    Which machine did you format the drive on? Different OS's also have different partition sizes.
    Dwight
  10. Replies
    82
    Views
    1,163

    Most TTL have very asymmetric currents for 1 to 0...

    Most TTL have very asymmetric currents for 1 to 0 than 0 to 1. The pullup is about 10:1 or more. Bus buffers are often closer to 1:1. An unloaded output will show an almost square wave but a high...
  11. Replies
    82
    Views
    1,163

    Good old Simpson. I have two around the house...

    Good old Simpson. I have two around the house someplace. I should have looked.
    I'll admit I recall looking at the inside a long time ago and thought it was some form of DC isolation. It was clearly...
  12. Replies
    22
    Views
    534

    Using an orange pencil eraser is something like a...

    Using an orange pencil eraser is something like a drug addiction. The more you use it the more you need to use it. First, they are made with rubber. To make rubber what it is, they add sulfur. Every...
  13. Replies
    49
    Views
    6,383

    I did a talk on my board at the "Virtual Vintage...

    I did a talk on my board at the "Virtual Vintage Computer West 2020". It is currently up on youtube. Just do a search for the quoted text. My talk starts at 2:54:37 and ends at 3:14:15. It was...
  14. Replies
    10
    Views
    401

    It wouldn't need more than you'd need for UPS....

    It wouldn't need more than you'd need for UPS.
    Dwight
  15. Replies
    82
    Views
    1,163

    I've not see such, that I remember, on a VOM. It...

    I've not see such, that I remember, on a VOM. It is much easier to just get a capacitor. They are not all to uncommon. I'd send you one but it isn't worth the postage.
    Dwight
  16. Replies
    6
    Views
    279

    For things like FluxEngine or Geaseleweazle, you...

    For things like FluxEngine or Geaseleweazle, you don't need to know the density but if you expect to use a computer with a controller, you need to know if it is FM or MFM as well. Not all newer...
  17. Replies
    82
    Views
    1,163

    Many VOMs are even worse. They just rectify the...

    Many VOMs are even worse. They just rectify the voltage with a bridge using copper oxide diodes. You connect 5 volts DC to a VOM and you are likely to read about 3 or 4 volts on an AC scale. As for...
  18. Replies
    19
    Views
    376

    How did you check that? Dwight

    How did you check that?
    Dwight
  19. Replies
    82
    Views
    1,163

    I would check the AC reading with a capacitor to...

    I would check the AC reading with a capacitor to isolate the DC path. Not all meters will read AC properly with a DC bias. A 1 or .1uf should be enough isolation for an AC reading with a typical DVM...
  20. Replies
    7
    Views
    163

    I would think it has unpredictable action. It is...

    I would think it has unpredictable action. It is possible that the intent was to make it come up in the local mode but without removing the connection to pin 1, I doubt it would be too reliable. I'd...
  21. Replies
    2
    Views
    82

    You are not likely to get far without a scope. (...

    You are not likely to get far without a scope. ( don't buy a cheap 1MHz scope. it is not fast enough to deal with the video circuit ). There is a schematic on the web.
    Dwight
  22. I still use Forth for all of my hobby project....

    I still use Forth for all of my hobby project. When I program, I make lots of mistakes. I've never found a language that I can produce working, debugged, code in such a short amount of time ( my time...
  23. Replies
    5
    Views
    187

    I should note that piggybacking is not a 100%...

    I should note that piggybacking is not a 100% valid test. A RAM could still fail in such a way that piggybacking doesn't work. It would be best to pull the RAMs and install sockets.
    Still, this...
  24. Replies
    5
    Views
    187

    First picture, upper left, as two columns of...

    First picture, upper left, as two columns of 2102s. These are generic parts so manufacture is not too important.
    Dwight
  25. Replies
    36
    Views
    2,626

    They use a 5V to 3.3v converter. 16 of the I/Os...

    They use a 5V to 3.3v converter. 16 of the I/Os are 5V tolerant ( at least for the BluePill ). For input TTL or CMOS is fine. For outputs it is recommended to use them as open drain and a pullup...
Results 1 to 25 of 500
Page 1 of 20 1 2 3 4