RE: Re: 1541C troubles

It can't find a sector header with the track number that it thinks it is 
at.  The search sequence does not appear able to step the head far enough 
to do a complete reset of the stepper mechanism.

On Fri, 6 Jul 2012, Bil Herd wrote:

> Do you mean it can't read _any_ track or that it can't read the
> _specific_ track that it thinks it is looking for?
>
> -----Original Message-----
> From: owner-cbm-hackers@musoftware.de
> [mailto:owner-cbm-hackers@musoftware.de] On Behalf Of William Levak
> Sent: Friday, July 06, 2012 1:29 PM
> To: cbm-hackers@musoftware.de
> Cc: hwarin@neuf.fr
> Subject: Re: Re: 1541C troubles
>
>
> It's not a problem of alignment.  It's a problem of programming logic.
> The drive occasionly gets in a state that the programmers did not
> anticipate.  The head moves, but does not do anything, because it cannot
> find the track it is supposed to be on.
>
> The fix is to step the head all the way out and then back in again.  The
> test routine does this.  You could also do this by issuing the commands to
> read track 35 and then track 0. A calibrated disk is not necessary, you
> only need a disk with the track and sector headers written correctly.
>
> Moving the head by hand sometimes works, but the test routine is more
> reliable.
>
> On Fri, 6 Jul 2012, hwarin@neuf.fr wrote:
>
>> William,
>>
>> This 1541C has not a problem to move the head and even if it's
> misaligned (it could not misalign that much in a minute or so) it should
> be able to format a simple floppy and read it back - To me, the problem is
> "somewhere" in read/write logic but I don't know where to start searching
> on this board revision.
>>
>>
>>
>> Regards
>>
>> Tous vos emails en 1 clic avec l'application SFR Mail sur iPhone et
> Android - En savoir plus.
>>
>>
>> ========================================
>>
>> Message du : 06/07/2012 07:18
>> De : "William Levak " <wlevak@SDF.ORG> A : cbm-hackers@musoftware.de
>> Copie à : hwarin@neuf.fr Sujet : Re: 1541C troubles
>>
>>
>>
>>
>> If 1541 drives crash while the head is too far out, they cannot find
>> their way back to the home position.
>>
>> Use the drive test routine on the demo disk to reset it. You will have
>> to load the test routine from another drive unit, and run it. It steps
>> the head all the way out and back in again. If this doesn't fix it,
>> you have a real hardware problem.
>>
>> On Thu, 5 Jul 2012, hwarin@neuf.fr wrote:
>>
>>> Hi, Friends
>>>
>>>
>>>
>>> I am in trouble with a recently acquired 1541C (white 1541 case, white
> newtronics mecanic) and I need your lights !
>>>
>>> My first remark when it arrived was that the fuse support was damaged
> and metal body support slightly blend. Except from this, noting noticeable
> and it was operating surprisely well.
>>>
>>> After few days of use it bruptaly crashed (in software I mean ...)
> while running a very recent C64 demo. Power cycled eveverything and
> thought all will continue to go allright for next dozen of years - but no
> !
>>>
>>> The drive work absolutely normally in apearance but is completely
> unable to read or write anything at all. Spîn motor works okay, stepper
> is also okay, IEEE communication is okay but it's impossible to read or
> even format any floppy disk.
>>>
>>> I've done all easy things - cleanned the head with isopropyl alcool,
> reseated all connectors, swapped both 6522, checked 12V and 5V but no
> change, it still won't read/format anything. I've searched the web for a
> situable service manual/schematics and found that my MainBoard is labelled
> 251854, what seems to be PCB#250448. I don't have any spare
> Mitsumi/Newtronics mecanic to swap so I can't determine if mecanics is
> definitely okay or not.
>>>
>>> The board has an hybrid UD1 as -02 a ROM UA2 as -01 and a gate array
> UC4 as -01 - This seems to be a very standard board.
>>>
>>> I've tested head's wire continuity that is okay for all wires but I
> can't find any reference for expected values - I've values for ALPS for
> pin 1-5 that should be 32 ohms - I'm currently at 24 ohms. If I take pin
> 1-3 or pin 3-5, I have 12 ohms, so, what seems to be coherent.
>>>
>>> Can anyone confirm value of 24 ohms for a good head in newtronics
> mecanic ?
>>>
>>> Does anyone have a better idea than removing the shield soldered under
> the PCB and reheat all points around UD1/UC4/UC5 plus all discrete
> components involved around ?
>>>
>>>
>>>
>>> Regards - Thanks for your help
>>>
>>
>> wlevak@sdf.lonestar.org
>> SDF Public Access UNIX System - http://sdf.lonestar.org
>>
>
> wlevak@sdf.lonestar.org
> SDF Public Access UNIX System - http://sdf.lonestar.org
>
>       Message was sent through the cbm-hackers mailing list
>
>

wlevak@sdf.lonestar.org
SDF Public Access UNIX System - http://sdf.lonestar.org

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