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. Although, not truly relevant to this post, most...

    Although, not truly relevant to this post, most meters do not read out true RMS. They rectify the AC signal and and take the peak multiplied by 0.7071 for the display. This only works for a perfect...
  2. Replies
    80
    Views
    2,098

    First to your question about the 2 lines late in...

    First to your question about the 2 lines late in the sweep. No, it is not from the D8 EPROM. It is only active on the first part of the sweep it is turned off by the signal on D8 20. When a TTL...
  3. Measure J8 9 to 8 AC Volts J8 1 to 3 AC volts...

    Measure
    J8 9 to 8 AC Volts
    J8 1 to 3 AC volts
    J8 5 to 3 AC volts

    J8 2 to 3 or 6 DC volts
    J8 4 to 3 or 6 DC volts

    Dwight
  4. Connect things up again and remeasure. Make sure...

    Connect things up again and remeasure. Make sure when doing DC measurements that the meter is set to DC.
    Those reading that you have look correct.
    Dwight
  5. Hi Dave_m Thanks for the clarification. The...

    Hi Dave_m
    Thanks for the clarification. The wiring makes sense now. I didn't look at the way they'd used the diode bridge.
    Dwight
  6. The schematic on Zimmers shows different pins on...

    The schematic on Zimmers shows different pins on connector 8. I'm using the schematic that ( I think it was ) Dave_m posted.
    It shows the center tap going to pin 4 and not pin 3.
    See...
  7. Replies
    80
    Views
    2,098

    I'd stop the video at different times and one...

    I'd stop the video at different times and one could see parts of the waveform. By looking at different times, I could piece the entire wave form together. I'm not sure how the camera you are using...
  8. Most of these reading are useless noise. With no...

    Most of these reading are useless noise. With no loads and using a high impedance meter, most of these number are just capacitive coupling of the windings.
    First thing to do is check to see which...
  9. First thing to look at is the ripple frequency....

    First thing to look at is the ripple frequency. If it is 60Hz, you have one bad diode. For ESR, you can look at the shape of the signal after the peak. There will be a curve on the up side and it...
  10. Replies
    13
    Views
    827

    When looking at U2, did you see anything with a...

    When looking at U2, did you see anything with a pulse?
    Dwight
  11. Yep, that would be the one. There is likely a...

    Yep, that would be the one. There is likely a couple of stud mount diodes between it and the transformer on the positive post of the capacitor. This is where a scope comes in handy. You can look at...
  12. If it is the RFI filters, open the supply up and...

    If it is the RFI filters, open the supply up and cut the RFI filters out. They provide little function purpose. They do offer some protection from line spikes but not much. You can replace them with...
  13. Burnt paper smell sounds like those nasty RFI...

    Burnt paper smell sounds like those nasty RFI input line filters. The transformers are switchers and don't usually have that much paper in them. Those filters produce lots of smoke and burnt paper...
  14. As for the +5V outs, many older regulators...

    As for the +5V outs, many older regulators required more than 2.5V head room. Not getting 9V where it is expected on the raw DC is an issue. It looks like the filter capacitor is missing or failed....
  15. Replies
    80
    Views
    2,098

    The math is just mathbut I'll break it all down....

    The math is just mathbut I'll break it all down. If I do a search for the 6502 instruction set it tells me that the NOP take two cycles. I know that the 6502 on the PET's runs at 1Mhz. There for,...
  16. The rectified DC voltage will be about...

    The rectified DC voltage will be about (1.4*ACV)-Diodes. If half wave the diode is about 0.6V. If center tapped full wave, the Diode is 0.6V. If a full wave bridge ( 4 diodes ) Diode is 1.2V.
    5V...
  17. I see no reason one needs to trace too much to...

    I see no reason one needs to trace too much to see where the signals go. It will amplify the tape signal and someplace turn it into digital tones. that should be easy enough to trace. If the circuit...
  18. Mike's pages has it: ...

    Mike's pages has it:

    https://deramp.com/downloads/mfe_archive/010-S100%20Computers%20and%20Boards/01-Optronics/10-Optronics%20S-100%20Boards/Optronics%20EPROM%20Programmer/

    Dwight
  19. Good information to know. So the +12 is...

    Good information to know. So the +12 is controlled by the windings as is typically done on these smaller supplies. It is a clever way to look for an over current. I'd never have thought of that. It...
  20. Replies
    80
    Views
    2,098

    First, the NOP generator is sending out addresses...

    First, the NOP generator is sending out addresses 0 to FFFF on a continuous loop. As different parts of the memory window are accessed, those that feed data to the buss will do that. The NOP takes...
  21. Tantulums will usually have a plus sign or a...

    Tantulums will usually have a plus sign or a white bar to indicate the polarity. Ceramic caps can also fail. These often don't have any numbers on them and are a brownish color. The ones with three...
  22. Visually, they look fine. I don't see any stuff...

    Visually, they look fine. I don't see any stuff leaking from under them.
    You could replace them but they are likely fine. Measure power rails and if you have a scope, look for ripple.
    Any capacitor...
  23. Replies
    80
    Views
    2,098

    The video actually works relatively well. It...

    The video actually works relatively well. It captures busts of video but since he'd only ran it for few seconds, I was able to piece things together. I'm not sure it is a missing strobe but that is...
  24. Replies
    80
    Views
    2,098

    That may not be needed. I'm doing a little math...

    That may not be needed. I'm doing a little math on the image of the video we do have. The address should be sequencing sequentially. If the picture you have is correct, we should be looking at data...
  25. That is interesting. Most smaller supplies use...

    That is interesting. Most smaller supplies use the 5V for regulation and the +-12V is done by winding count ( or in some cases an analog regulator ). They do often run the regulator circuit from the...
Results 1 to 25 of 500
Page 1 of 20 1 2 3 4