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Type: Posts; User: Dwight Elvey

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  1. It looks like the cards you have from the bottom...

    It looks like the cards you have from the bottom are:
    32K RAM
    Bus interface
    Floppy controller
    Serial card??

    The top card doesn't look like my serial card or a parallel card. I'd be curious...
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    No The speed of the EPROM to read data in a...

    No
    The speed of the EPROM to read data in a programmer is different than in a system. A weakly programmer cell can be slower to bring the programmed level to the output. In a system that requires...
  3. This part of the circuit can be tested with a...

    This part of the circuit can be tested with a voltmeter and a piece of wire, you don't need a logic probe.
    It will jump back if it is stopped before it advances again. The is not that it is trying...
  4. You need to trace the track00 circuit. 4F pin 11...

    You need to trace the track00 circuit. 4F pin 11 should track the switch. Watch T8. It should not toggle when the head is moving away from track00 and should stay high.
    Like wise 3D pin 2 should...
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    How about the handshake wires? Dwight

    How about the handshake wires?
    Dwight
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    Great Dwight

    Great
    Dwight
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    Without special setup, there is not much else you...

    Without special setup, there is not much else you can do. The head alignment usually only aligns one head, assuming the other head was right to start.
    Dwight
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    Forget what I just said, you drive has three...

    Forget what I just said, you drive has three pots.
    Dwight
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    With the disk out, carefully lower the head down...

    With the disk out, carefully lower the head down by closing the door slowly. Most double heads have opposite flat sides such that only a narrow part overlaps ( the width of a track ). You don't want...
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    It is also hoped that you measures the pots value...

    It is also hoped that you measures the pots value before you adjusted it? The pot sets the write current.
    With the tracking being a little off, it would read a disk formatted by by itself. The...
  11. It could be one of the XORs or 3D but my bet is...

    It could be one of the XORs or 3D but my bet is still with the Zero switch. He didn't say it would step away from track zero when it was suppose to be stepping towards track zero, only that it would...
  12. Opps. I should have said 4F pin 10 stuck high not...

    Opps. I should have said 4F pin 10 stuck high not low. When both pins of 4F were one, it would block the step pulse. Anyway, the same problem the switch is stuck or something in the switch path. 4F...
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    Try a little more weight to see if it is still...

    Try a little more weight to see if it is still contact issues.
    Also check the rotation speed.
    Dwight
  14. My bet is a stuck or broken track 0 switch. It...

    My bet is a stuck or broken track 0 switch. It thinks it is always at track zero and that won't let it go any more towards track zero, it is locked out by 4F pin 10 being stuck low.
    Dwight
  15. It is interesting that different training makes...

    It is interesting that different training makes one see things differently. When looking at logic diagrams, I don't tend to look a them in terms of positive or negative logic. I only look at them...
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    Here is a manual for your board....

    Here is a manual for your board.
    http://www.s100computers.com/Hardware%20Manuals/MITS/88_4kdrb.pdf

    Be careful about that extra regulator. It may be for the negative rails of the RAMs. You'll have...
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    That is good and bad to hear. ( bad for the...

    That is good and bad to hear. ( bad for the memory card )
    With the boards removed, you can do a quick check data in lines by grounding them on the bus. It is a simple test to make sure when you have...
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    I've used GeoffB17's method for years and never...

    I've used GeoffB17's method for years and never had an issue. The key is to wipe the disk CLEAN with a strong magnet. Only format or write to is on the 1.2M drive!
    Dwight
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    What is the clock rate used by the keyboard UART?...

    What is the clock rate used by the keyboard UART? Looking at the schematic, it isn't clear. That divided by 128 or 144, depending on which of stop counts are used would be the fastest half cycle you...
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    When you reset, your video showed the address...

    When you reset, your video showed the address lights all lighting because of the buffers are going 3state. My question is that do all the addresses light in sequence when you increment the address....
  21. Here are some pictures of my machine: The last...

    Here are some pictures of my machine:
    The last picture is looking down into the rack. Notice that there are two long UCB strips. The large card strattles the two busses. The RAM card is 8Kb of high...
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    The speaker is controlled by a bit from a uart...

    The speaker is controlled by a bit from a uart data. The rate that you could toggle is controlled how fast you can send 8 bits of data over the serial. To complicate things, the serial is a...
  23. I wonder if it was able to switch between AIM65...

    I wonder if it was able to switch between AIM65 controlling the bus and RM65 controlling the bus. The one shown was used with the AIM65 only controlling.
    Dwight
  24. That was where I'd seen the RM65 FDC manual. It...

    That was where I'd seen the RM65 FDC manual. It was apparently used with the AIM65 sometimes. I'd assume that they made an adapter to UBC or STD bus, from the AIM65, at sometime.
    Dwight
  25. I'm assuming this was for the Siemens system your...

    I'm assuming this was for the Siemens system your working on?
    Dwight
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