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Type: Posts; User: Dwight Elvey

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

    When looking at U2, did you see anything with a pulse?
    Dwight
  2. 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...
  3. 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...
  4. 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...
  5. 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....
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    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,...
  7. 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...
  8. 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...
  9. 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
  10. 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...
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    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...
  12. 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...
  13. 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...
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    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...
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    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...
  16. 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...
  17. Replies
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    Here is the math. Running at 1MHz, the full...

    Here is the math. Running at 1MHz, the full address space is 65536 adrresses. We are only interested in 1/16th of that space, while the EPROM pin 20 is low. Each full address pass should be 131.072...
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    If I stop the video right at the first part of...

    If I stop the video right at the first part of the trace, I think I can see what I'm looking for. If it is just the ch2 on the screen, I can see highs and lows right at the start for about 1/3 of a...
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    You are turning the sweep the wrong way. Try...

    You are turning the sweep the wrong way. Try something like .5 or .2 milliseconds and turn the intensity up. Also where are your 0V lines?
    The video is good as I can stop it at various places....
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    Once we show that the processor can read one...

    Once we show that the processor can read one location in a EPROM we can write some simple loops to test targeted locations with tight loops.
    Dwight
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    Nope, 2716 should work without an adapter in the...

    Nope, 2716 should work without an adapter in the 2001N.
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    Hi Miata I don't think you can plug a 2716 or a...

    Hi Miata
    I don't think you can plug a 2716 or a 2732 directly into a 6332 socket without an adapter socket. Some of the pins will be wrong.
    Dwight
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    Hi Dave This was a working system once. The...

    Hi Dave
    This was a working system once. The chance of crossed data line other than adjacent line is quite small. 01010101 and 10101010 should check for adjacent shorts. I'm mainly looking for...
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    I'm not sure what we are looking at. Are you...

    I'm not sure what we are looking at. Are you getting a stable trigger on pin 20 of the EPROM. We are only interested in the first part of the signal after the falling edge of the signal on pin 20....
  25. Most are too low a resistance for the high...

    Most are too low a resistance for the high voltage side. It is better to have some permanent resistors attached all the time. Especially on those with voltage doublers. If discharged in the wrong...
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