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bdurbrow

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  1. Could you design in the extra hardware to operate bidirectionally, and just not populate that area of the PCB for the unidirectional boards?
  2. bdurbrow

    Diagnostic software

    I don't recall any diagnostic software ever outputting over SCSI... but that doesn't necessarily mean that there never was any. As for which software to use, it depends on which Mac you are having trouble with.
  3. bdurbrow

    Macintosh crt related deaths

    Or, if you do, you are also implicitly specifying the resistance of the circuit. R=V/I - "Ya canna' violate the laws of physics, cap'n!" Lt. Cmdr Montgomery Scott. I think it depends on who "you" is, and how unlucky you are. Sometimes people have heart conditions that they don't know about. On the other hand, I just got back from traveling at a closing speed of over 120 miles per hour in close proximity to other vehicles being operated by a bunch of yahoos... any error during the course of which could well have been fatal (and indeed, something in the neighborhood of thirty-two thousand people die each year in the US alone from this activity). I'm probably going to do it again tomorrow, too... What is this insane activity I speak of? Why, just going out to get lunch... and doing so in a car.
  4. bdurbrow

    Macintosh crt related deaths

    FWIW, it's a common myth (er, oversimplification, really) that electricity takes the path of least resistance - it actually takes ALL paths, but how much flows thru any given path depends on the resistance of that path as compared to the rest of the paths. If, for example, you have a positive source connected to your right thumb, and a negative source connected to your right pinky finger, there will be some flow thru your heart - but it will be vastly smaller than the flow from your finger to your thumb, because the resistance of the path that goes thru your heart is so much greater. Usually, that difference is enough to make getting a shock that primarily goes thru a path other than across your heart a painful but non-fatal occurrence - and CRT's generally fall into this category. Large high-voltage power supplies however, are a different story; getting shocked by an industrial power connection can kill you even if the primary path is just thru some other part of your body. Also, for high current discharges, inductive effects can come into play - lightning strikes, for example, tend to do this (most of the power of a lightning strike flows over the surface of the object being hit, but that much current makes quite the inductive whollop to anything conductive nearby). Other factors can also come into play - your skin resistance, for example, is much higher when dry than when wet (and it's even worse when sweaty, with all the electrolytes in the sweat making it a good conductor); but the resistance of your insides is much lower than your skin in general. Wearing gloves in general is a good idea when working with high voltage; but make sure that they can breathe so that you don't get sweaty in them.
  5. bdurbrow

    Mac SE FDHD - Disk Drive "Stuck", Buzzing

    Also known as "spudgers" - and no, I have no idea where the name came from. But - yeah, they're great to have around; especially for those doggon' FFC connectors.
  6. bdurbrow

    Mac SE FDHD - Disk Drive "Stuck", Buzzing

    Both my 128k and SE won't open just by gentle shaking... but, they are early machines, so perhaps the molds they were made from were a bit tighter than yours? IIRC, the Aquadag on the inside of the CRT is pulled to positive 15 to 30 kv or so relative to ground (which is why that terminal is called the anode - it's positive), by a high voltage transformer and diode arrangement. Usually this high voltage circuit is completely enclosed in a high-voltage insulator, and there isn't any high voltage on the driver PCB itself, but I'm not familiar with the specifics of the SE's high voltage drive circuit, so I can't say for certain that there is no exposed points on the Analog Board that carry the CRT anode voltage. To make the obligatory automotive analogy, it's like working on a car: if you go in with no clue, and start poking about at random, you could very well end up having a very bad time ("gee, what's this smelly stuff in the big tank in the back? I wonder what'll happen when I try to use my grinder on it?"). But, if you take some time to do proper research before starting, you'll probably be OK ("Ahh, there's gasoline coming out of that fuel hose I just unclipped and capped off; better let it fully evaporate and clear out of the air around here before starting anything that could be an ignition source. Also, good thing I'm wearing nitrile gloves and have plenty of ventilation going."). If you do that, be sure to post it on YouTube, so that the rest of us can ridicule you, er, I mean, uh, be informed as to the results of such an action.
  7. bdurbrow

    Mac SE FDHD - Disk Drive "Stuck", Buzzing

    Umm... that's a Torx T15, not a T8. Also, a sheet metal spring clamp to pry the case open after removing the screws is handy. Ditto on the not-electrocuting yourself part. Compact Macs have CRTs in them that retain high voltage even when turned off and unplugged... and there's enough capacity in the CRT to cause your heart to stop if you get the current flow thru your body just wrong - and if you do happen to survive, I'm told that it really, really hurts. So, make sure you discharge the CRT before digging around inside it. If you are not comfortable doing this; then it's best to have somebody else who has good skills working with CRTs and high voltage do it. And once you do get in there; be careful of the neck of the CRT - it's quite fragile, and you really, really don't want to bap it with your hand (which is really easy to do when pulling up on the connectors to get the motherboard or drives out).
  8. bdurbrow

    Bare-metal Mac project

    You are in a maze of twisty little wires, all alike. >
  9. bdurbrow

    Apple 2c disk drive leaking something??

    Well, I'm no expert on ][ drives, but... That looks like an inductor; and if I'm right, then there's nothing inside it to be leaking out. I agree with Joe - it's most likely glue; commonly called "Silastic" (even though that's a trademark; see https://en.wikipedia.org/wiki/Silastic --- kinda like asking for a Kleenex or a Xerox, even though you're going to be handed a generic facial tissue and a photocopy made on a machine manufactured by Cannon or HP). It might help if you could be more specific about what, exactly, it's doing? And are the symptoms specific to that particular drive, or could it be the controller or a disk that's at fault? Can other drives read disks formatted and/or written by that drive? Or vice-versa?
  10. bdurbrow

    Dodged the SE battery bullet!

    Oh, and it's still got some charge on it: a whole whopping 50 millivolts!
  11. bdurbrow

    Dodged the SE battery bullet!

    So, I just popped open that SE that I was given, fearing the worst... but, NO! No acid spilled across the Logic Board: ... and that battery has a date code of 6/88!
  12. bdurbrow

    Micron Xceed docs on ebay

    There are FPGAs that can do DVI and HDMI directly; and I have here an FPGA dev board (Papillo with an Arcade MegaWing) that does VGA via a R2R ladder.
  13. FWIW, I have a 128K Mac that's been upgraded with a Levco Monster Mac card, and the Mac Plus ROMs... that wouldn't boot. At first I thought it was the EPROMs on the Monster Mac card that had died (they were found to be missing the UV shielding cover that keeps them from being slowly erased), but it turned out to be the mask ROMs on the main Logic Board.
  14. bdurbrow

    Just got a Mac Plus--I have questions.

    It's probably making a bunch of Color QuickDraw calls; even if the display is in single-bit-per-pixel mode.
  15. bdurbrow

    Just got a Mac Plus--I have questions.

    The video on a compact Mac is TTL, and not at a standard frame rate. For streaming, you would probably be better off running the games in an emulator and streaming that out via a video capture app on your modern Mac/PC. In principal one could create some new hardware to capture the TTL video and input it via USB (perhaps with a fast ARM micro controller that had a high-speed USB 2 port on it), but it would be a non-trivial project.
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