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Thread: Tandy 2000 FDC chip question

  1. #61
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    Quote Originally Posted by kb2syd View Post
    It's me. Call sign is different but same old Kelly. Been laying low for no good reason.
    call sign looks the same to me, but I can't tell my heini from my elbow. Don't be a stranger, ay?

  2. #62
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    So not quite out of the woods.. one of the drives does not work quite right. It can format, write and read its own disks. It can sort of read the directory on some disks. It cannot read files. The other drive can read and run anything the faulty drive writes though.. which in my experience is not the usual situation.. what do you guys think? Alignment?

  3. #63
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    Alignment would be my vote; the symptoms are correct. However, before you go tweaking that adjustment, make sure that the Track 0 sensor is clean. Get some crud in there and where track 0 lies goes out the window.

  4. #64
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    "Quad Density" drives like the ones in the Tandy 2000 never had a great reputation for reliability, unfortunately. They existed since the late 1970's but issues with alignment and whatnot contributed to them never ousting the 40-track variety.
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  5. #65
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    Dunno about that--I'm still using a pair of Teac FD55F drives. Good workhorses. I've also got one of the last FH 5.25" 720K Micropolis models, the one with buffered seek. Good heavy-duty drive.

  6. #66
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    Quote Originally Posted by Chuck(G) View Post
    Dunno about that--I'm still using a pair of Teac FD55F drives. Good workhorses. I've also got one of the last FH 5.25" 720K Micropolis models, the one with buffered seek. Good heavy-duty drive.
    I wasn't really there at the time, so my statement is mostly based on vaguely remembered hearsay from old issues of "80 Microcomputing" implying that they were at least measurably more finicky. (Which isn't a completely unreasonable statement given the tighter tolerances, etc.) Some of that may well have been blowback over the short-lived war between the mutually-incompatible 96 TPI and 100 TPI variants.
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  7. #67
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    From a design standpoint, the 100 tpi drives had an edge over the 96 tpi ones. Track 0 on a 96 tpi drive is about Track 6 on a 100 tpi one. In addition, 100 tpi use only 77 tracks, as opposed to 80 on the 96 tpi drives, so 100 tpi is shifted away from the hub in comparison, giving better recording characteristics.

    Although I'm not certain about it, I believe that the 96 tpi drives were retrodesigned to be compatible with the original 48 tpi ones.

    Old Micropolis 100 tpi drives are battleships; heavy things with leadscrew positioners and, I think, 4 steps per track. Not the fastest, but very reliable--and expensive.

  8. #68

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    Quote Originally Posted by Eudimorphodon View Post
    I wasn't really there at the time, so my statement is mostly based on vaguely remembered hearsay from old issues of "80 Microcomputing" implying that they were at least measurably more finicky. (Which isn't a completely unreasonable statement given the tighter tolerances, etc.) Some of that may well have been blowback over the short-lived war between the mutually-incompatible 96 TPI and 100 TPI variants.
    I never had issues with 80-track 96tpi drives. I had a couple of them in my TRS-80 Model 4 (FH drives), another friend had two Mitsubishi drives for his Ampro (the same model as the Model 2000), and another friend had a couple of Teac FD55F drives for his Ampro. We swapped floppies back and forth and never had any issues reading each other's. Even today I can still read my old floppies with other 96tpi drives.

  9. #69
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    The lousy built-in data separator circuitry on the Model I might also have been a factor in the griping, although I can't really think of a good reason why a properly aligned 77/80 track drive would necessarily give a messier/weaker signal than a 40 track one.
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  10. #70
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    The part I can't figure out in my case is why the working drive is able to read what the 'bad' drive is creating no problem. I thought with alignment issues, if you formatted and wrote stuff on a bad drive only the bad drive would be able to read it?

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