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Thread: 1571 read errors / Can't format?

  1. #1

    Default 1571 read errors / Can't format?

    Hello again!

    Yet another project I've just started on... I have a C128 DCR which is all in order (recently finished that one)... I just picked up another 1571 as an external drive.

    Currently, I'm controlling it via ZoomFloppy on my Mac. Before I pull the 128 out of it's nest, I want to have this thing in good order to try to keep my office tidy. The problem is that the external 1571 throws read errors.

    Symptoms:
    * It cannot read the directory on a known good disk: 27,read error,18,00
    (This is true for all known good disks)

    * It cannot format a known good disk: 21,read error,00,00

    Here are some more detailed errors that cbmforng will spit out at me:

    21,READ ERROR,01,55
    Track|Retry|sctrs|slctd|| GAP |modulo |modulo|tail| Verify | RPM |
    | | | GAP ||adjst|complmt| dvsr |GAP | | |
    -----+-----+-----+-----++-----+-------+------+----+---------+------+
    1 | | 21 |$05.0||$06.8| $02.8 | $08.0|$094|SYNC fail| 0.00|
    1 | 1 | 21 |$04.8||$07.0| $03.8 | $07.0|$09D|SYNC fail| 0.00|
    1 | 2 | 21 |$09.0||$02.8| $04.8 | $06.0|$042|SYNC fail| 0.00|
    1 | 3 | 21 |$06.8||$05.0| $01.8 | $09.0|$077|SYNC fail| 0.00|
    1 | 4 | 21 |$05.0||$06.8| $03.8 | $07.0|$093|SYNC fail| 0.00|
    1 | 5 | 21 |$04.8||$07.0| $02.8 | $08.0|$09E| ./. |300.46|
    1 | 6 | 21 |$0B.0||$00.8| $04.8 | $06.0|$01A|SYNC fail| 0.00|
    1 | 7 | 21 |$07.8||$15.8| $09.0 | $01.8|$1CB|SYNC fail| 0.00|
    1 | 8 | 21 |$05.8||$06.0| $02.8 | $08.0|$08A|SYNC fail| 0.00|
    1 | 9 | 21 |$04.8||$07.0| $03.8 | $07.0|$09D|SYNC fail| 0.00|
    1 | 10 | 21 |$09.0||$02.8| $03.8 | $07.0|$043| ./. |300.48|
    1 | 11 | 21 |$0B.0||$00.8| $03.8 | $07.0|$01B|SYNC fail| 0.00|
    1 | 12 | 21 |$07.8||$04.0| $02.8 | $08.0|$062|SYNC fail| 0.00|
    1 | 13 | 21 |$05.8||$06.0| $02.8 | $08.0|$08A|SYNC fail| 0.00|
    1 | 14 | 21 |$04.8||$07.0| $03.8 | $07.0|$09D|SYNC fail| 0.00|

    *) Note: The fractional parts of all the GAP based numbers shown here
    (sedecimal values) are given due to nybble based calculations.

    I'm not 100% sure what's happening here, but I think that the formatng command is doing a more "manual" format or something, so it's directing writes to specific locations and verifying what's happening. That's just a guess. More importantly, the order of the errors that that returns changes every time I run it, which *seems* like a sort of good thing maybe? (possibly indicating that this isn't a hardware fault)

    I had been thinking this could be an alignment problem, but I would *expect* a misaligned drive to still be able to format something, even if nothing else can read it.


    I have the drive partially disassembled on the workbench. Here's what I have done and what I can confirm:

    * The drive heads move
    * The heads appear to be in good condition. I cleaned them and there wasn't much on them.
    * The heads seek to track 0 and to track 18 with no obvious issues. When trying for a directory, they appear to hunt around track 18 a bit.
    * The mechanism closes firmly and well. The ejector spring was disconnected, but that's been corrected.
    * The disk spins freely and the motor sounds just fine.

    Suggestions? I'm trying to avoid pulling my 128 out of it's spot to run 128 diags from there, but I will if I have to... Though I am just starting to wonder if I can control the ZoomFloppy from vice...
    Thanks!

  2. #2
    Join Date
    Jan 2012
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    Default

    The 1571 is a very reliable drive, and I've never come across one that is genuinely out of radial alignment. As you say, even if it was, it would usually format and read it's own disks just fine.

    The most common fault with 1571's is that if they have been left for years with the drive in the open position, the top head slowly sags on it's springs, meaning it doesn't sit in the correct position. The way to determine this is to use the drive in single sided mode, either by using it in a 64, or by sending "u0>m0" if using a 128. Then try and format a disk. If it works, that's your problem. Unfortunately there's no fix for this other than replacing the heads.

    Less common problems can be the integrated logic package at U7, but you'll need a scope to identify the problem reliably.

    Rob

  3. #3

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    Quote Originally Posted by crock View Post
    The 1571 is a very reliable drive, and I've never come across one that is genuinely out of radial alignment. As you say, even if it was, it would usually format and read it's own disks just fine.

    The most common fault with 1571's is that if they have been left for years with the drive in the open position, the top head slowly sags on it's springs, meaning it doesn't sit in the correct position. The way to determine this is to use the drive in single sided mode, either by using it in a 64, or by sending "u0>m0" if using a 128. Then try and format a disk. If it works, that's your problem. Unfortunately there's no fix for this other than replacing the heads.

    Less common problems can be the integrated logic package at U7, but you'll need a scope to identify the problem reliably.

    Rob
    Ahhhhh... prior to reading this, I kept reading about this deflection... I can't really see it, but I've found that if I sort of nudge/support the head arm that rests on the head lifter when the drive is open, it tracks across tracks and formats the disk!

    So... How exactly does this thing need to be bent? As I said, I can't see any "bend" in it now! I'm assuming (probably incorrectly) that it's the copper-looking piece that needs adjusting?

    IMG_3246.jpg

  4. #4

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    Quote Originally Posted by crock View Post
    The 1571 is a very reliable drive, and I've never come across one that is genuinely out of radial alignment. As you say, even if it was, it would usually format and read it's own disks just fine.

    The most common fault with 1571's is that if they have been left for years with the drive in the open position, the top head slowly sags on it's springs, meaning it doesn't sit in the correct position. The way to determine this is to use the drive in single sided mode, either by using it in a 64, or by sending "u0>m0" if using a 128. Then try and format a disk. If it works, that's your problem. Unfortunately there's no fix for this other than replacing the heads.

    Less common problems can be the integrated logic package at U7, but you'll need a scope to identify the problem reliably.

    Rob
    Ah ha! Never mind... Not the copper piece. Just a bit of a twist to the left and it seems to be all squared away!

  5. #5

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    Quote Originally Posted by dhoelzer View Post
    Ah ha! Never mind... Not the copper piece. Just a bit of a twist to the left and it seems to be all squared away!
    The top head of a 1571 is lifted by only one side support. This causes after many years a little twist in the head orientation and it's not sitting flat against the disk surface anymore, plus isn't pushing the disk surface flat against the bottom head anymore, so effectively a 1571 with this problem can barely read/write bottom surface (side 0) and can't read/write top surface.
    I've fixed a couple of these drives by gently twisting counter-clockwise the top head assembly. Very gentle twist, then try again, then again a twist if it didn't solve it... With a few trials usually the drives read/write perfectly again.
    Frank

  6. #6

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    Quote Originally Posted by iz8dwf View Post
    The top head of a 1571 is lifted by only one side support. This causes after many years a little twist in the head orientation and it's not sitting flat against the disk surface anymore, plus isn't pushing the disk surface flat against the bottom head anymore, so effectively a 1571 with this problem can barely read/write bottom surface (side 0) and can't read/write top surface.
    I've fixed a couple of these drives by gently twisting counter-clockwise the top head assembly. Very gentle twist, then try again, then again a twist if it didn't solve it... With a few trials usually the drives read/write perfectly again.
    Frank
    Yep... The gentle twist did fix it... but after formatting a stack of disks I started to see it become unreliable again... Gave it a bit more of a twist for temporary relief. Has anyone come up with a long term fix? I'm wondering if the years of twisting has made it want to return to the twist.

  7. #7

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    Quote Originally Posted by dhoelzer View Post
    Yep... The gentle twist did fix it... but after formatting a stack of disks I started to see it become unreliable again... Gave it a bit more of a twist for temporary relief. Has anyone come up with a long term fix? I'm wondering if the years of twisting has made it want to return to the twist.
    The only "fix" that I've found is to never ever leave a 1571 door open, unless when extracting a disk (of course).
    It may take some time to find the correct amount of twist to correct it. Give too much twist and things get worse... It's a kind of magic

    Frank

  8. #8

    Default

    Quote Originally Posted by iz8dwf View Post
    The only "fix" that I've found is to never ever leave a 1571 door open, unless when extracting a disk (of course).
    It may take some time to find the correct amount of twist to correct it. Give too much twist and things get worse... It's a kind of magic

    Frank
    I had planned that, but I noticed that without a disk in tyhe drive, the arm just to the left of the rail that the head arm rests on sticks up and supports the head arm.

  9. #9
    Join Date
    Jan 2012
    Location
    Zurich, Switzerland
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    Quote Originally Posted by dhoelzer View Post
    I had planned that, but I noticed that without a disk in tyhe drive, the arm just to the left of the rail that the head arm rests on sticks up and supports the head arm.
    Sent you a PM.

  10. #10

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    Quote Originally Posted by dhoelzer View Post
    I had planned that, but I noticed that without a disk in tyhe drive, the arm just to the left of the rail that the head arm rests on sticks up and supports the head arm.
    Yes, sorry, I should have mentioned that I also have the cardboard "dummy" insert. That releases the top head lifting mechanism, like when a normal floppy is inserted. Sorry, it's been a while since list time I've used the 1571.

    Frank

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