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Thread: Testing and/or troubleshooting Model III floppy drives

  1. #21
    Join Date
    Oct 2019
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    Richland, WA (USA)
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    28

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    Quote Originally Posted by Patrick Bureau View Post
    oh quite possible
    Thanks, I ordered a replacement from Eastern Europe so hopefully will have an update in a few weeks. It's labeled as a WD1691-PE versus the WD1691V in mine but hopefully that doesn't make much difference.

  2. #22
    Join Date
    Oct 2019
    Location
    Richland, WA (USA)
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    28

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    Success! On the controller front at least.

    The replacement chip arrived yesterday and I put it in tonight. It booted right into the images off the Gotek/FlashFloppy in the Drive 0 cable position and for the first time ever I had something besides Cassette BASIC running on my stalwart old TRS-80

    No luck booting from an actual disk in the one working drive yet, but a simple BASIC test program is able to at least see some sort of data stream coming off of it. Maybe just a matter of alignment now. I'm debating whether to just mount the Gotek permanently in this, or plow through and get one/both drives working again; probably gonna go for the latter.

  3. #23
    Join Date
    Jun 2018
    Location
    Pacific NW in the islands
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    105

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    look for the model III diagnostics and run the drive alignment program. you won't have the alignment diskette so you can't check head radial (which isn't your problem, anyway, if your drive isn't even stepping), but you should be able to check for index pulses and track zero indications. i admit that i never ran these diags without an alignment diskette so YMMV. don't do any alignments, just check signals... that may show you a path forward. with the additional info listed below, you should make sure that you have the proper drive handshake/status signals making it out of the drive and to the FDC. you should have a scope for this, but at a minimum you can construct a logic probe inexpensively. it won't give you timing, but should show you activity. lots of plans on the internet and they are even available from that great internet retailer...

    if you haven't downloaded the MIII Technical Bulletins, now would be a good time to do so. they'll give you some info about the machine. as well, Notes and Jumpers will provide additional information. more information is better! Also, service information for those drives is available... either RS or Tandon. Should be a theory of op in there. if you're not familiar with how the drives work and what they expect be sure to find a good theory of op before poking around.

    On the FDC alignment: so it's been a zillion years since i did one, but it's not difficult if you have all the test equipment. i don't recall if the alignment diskette is required for that. i don't suggest you do this, just FYI.

    i've attached a Model III file from TS training that gives a tech-centric overview. ignore the weird formatting--this was before we had nice GUI word processors... anyway, there's a little bit on the FDC and drives which might help.
    Attached Files Attached Files
    Last edited by shank; March 17th, 2020 at 09:06 AM.

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