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Thread: Strange issue with New Percom Doubler

  1. #1

    Default Strange issue with New Percom Doubler

    Some of you old time Model I users, what the heck is causing me some crazy strange issues with double density disks.

    I am using calibrated drives, that are aligned right and the lobes and clamping are correct, and have tried freshly formatted disks using a Model III using the same drive on the Model I.

    Single Density works correctly. Double Density is erratic as best. I get data record locked, HIT, Directory read errors, etc. This is more than one drive.

    Drives are terminated right (Well I'll double check that its not in backwards). I cleaned the card edge, no difference. This just started.

    I'm thinking it might be one of the two controllers going out on the doubler board, but not sure if anyone has any thoughts on if its a support chip dying.

    LDOS 5.3.1 and yes, FDUBL (P) is being used.

  2. #2
    Join Date
    Jun 2015
    Location
    Sioux Falls SD
    Posts
    179

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    Can you try another DOS? I've generally had good luck in DD using DOSPLUS 3.5.

    If SD works correctly with the board installed, that would indicate that the 1771 is good, especially if you can copy a TRSDOS 2.3 disk with the DAMs that only it can read.

    Can you test the doubler in another EI?

  3. #3

    Default

    Quote Originally Posted by lafos View Post
    Can you try another DOS? I've generally had good luck in DD using DOSPLUS 3.5.

    If SD works correctly with the board installed, that would indicate that the 1771 is good, especially if you can copy a TRSDOS 2.3 disk with the DAMs that only it can read.

    Can you test the doubler in another EI?
    Yeah I have another EI. Unless its the same chip in a Model III, I dont have any extra double density chips to drop in the controller to test. (I read and understand the 1793 is an inverted bus versus the 1791). I'll see if I have another 1791 if I get that far.

    I'll also test TRSDOS 2.3, and DOSPLUS. Heck I could have a corrupt FDUBL and not even know it.
    Last edited by Tibs; May 16th, 2018 at 02:15 PM.

  4. #4

    Default

    Yeah itís the doubler. No dos can operate in double density mode right. I reseated the doubler no change. I donít have the fdc chip but I can check the support chips with stock

  5. #5

    Default

    I think I might have figured it out. Interference from the hard drive. I thought it was the monitor. Surprised to say the least I donít know if itís the cable or the unit doing it. Itís an 8x00 12 megger

  6. #6
    Join Date
    Sep 2011
    Location
    Melbourne, Australia
    Posts
    962

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    Are you typing FDUBL or FDUBL (PERCOM)?

    FDUBL on its own defaults to Tandy doubler which was incompatible with the Percom / NewPERC
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

  7. #7

    Default

    Yeah, its not that simple I wish it was that simple trust me. I'm about done with this thing permanently - so irritated right now its time to quit for the night.

    Without the hard drive, doubler works fine.
    With hard drive, doubler doesnt work in double density mode but hard drive works fine.
    With hard drive sometimes even without the doubler, floppies may or may not work properly (Really this is more when the EI board is back in the case)
    I changed the M1 hard drive adapter, no difference. Hard drive works perfectly fine on the other computers I have, passes all diagnostics too. Same cable, checked it a few times tonight just to be sure.
    Changed the EI board, no difference, everything above still happens, I was convinced it was interference earlier.

    I haven't changed the Model I CPU unit out (The whole thing, not a part), I'll do that next. If the EI board isn't installed in the case (either board) I'm not having near as many issues, then I put everything back in and it misbehaves. Thats why I kept thinking it was noise form a cable or the video monitor causing something weird to happen. Its not heat related, the bottom isnt even on the EI case and things start getting weird.

    This is really the weirdest thing I've ever dealt with, because it makes no sense.

    Best I can describe when the floppy drives try and do stuff they get really weird, like they are out of alignment, and this is with or without the doubler, and different 1771s as well.

    I guess I could have an issue in the keyboard unit, since everything ties together between these.

    Oh, and they are all gold card edges, so not oxidation. These are final design EI boards, not buffered.

    FreHD does similar things. I'll try my MISE/MIRE with keyboard unit too.

    I'm so in the weeds with it I should have stopped when I was tired, three hours ago.

    I could leave the EI board out of the case completely, keep everything connected, and it would work (Double does not like the hard drive though).

    These components have all been together for almost a year without any changes, just started acted weirder and weirder and finally today couldn't ready double density disks.

  8. #8
    Join Date
    Sep 2016
    Location
    Melbourne, Australia
    Posts
    614

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    Sounds like an addressing or driver/patch conflict with the doubler and the HD controller.

  9. #9
    Join Date
    Jun 2015
    Location
    Sioux Falls SD
    Posts
    179

    Default

    Could a solder joint have failed where you're getting noise on the ground plane? Different behavior of EI in and out of the case seems strange.

  10. #10

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    Yeah, I sat up for a few hours brainstorming this. When you get in the weeds you lose all sense of where you are and where you've been in testing.

    I'll start from scratch. I have to first make sure my FreHD isnt bad. I have a MISE as well. I'll test them on my bench system to make sure all three of them work. (TRS-80 Drive as well)

    Then once I rule out the external drive adapter/drives I'll focus on the EI (and I can switch it with a MISE).

    Once I make sure that isnt the issue I'll go back to using a doubler.

    I'll sort it all out before I try but I have had to troubleshoot complex enterprise IT systems in the past and you just have to do one thing at a time, and last night I was getting 10 things at a time at the end. I think I might have a bad power supply in the EI. I didnt even check the basics, the voltage.

    David, I took someones advice might have been you. DOSPLUS does same thing. TRSDOS 2.3 works as does all three OS. I have used virgin master disks to make sure no corruption and same results. So I am pretty sure its not software related, its something simple that I'm just missing.

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