Re: Apple 400k drive

Hello Patrick,
and greetings from Helmut Post!
Do you remember me?
My third IDE File is running very well!
Back to the topic: What is the exact part description of the passive hall sensor?
Perhaps I know a place where to get obsolete and very hard to find parts.
Lately I purchased 2 Z8 processors (Zilog 8631) with 4 KB XROM for the 10 MB Profile - these are very hard to get, but there are still at least more than 40000 pieces left today. The price was $ 4.06 for each part.

Helmut

On 8 Mrz., 08:24, PSchaefer <dr.p.schae..._at_email.domain.hidden> wrote:
> On 7 Mrz., 21:18, "Terry Stewart" <te..._at_email.domain.hidden> wrote:
>
> > I've been in discussion with folk on the classic computer mailing list about
> > this.  The feeling was it could have either been the TA7259 motor controller
> > IC, the associated caps or on of the hall-effect devices in the motor
> > controller IC itself.  
>
> Usually this is attributed to the hall effect sensors which get a
> voltage offset.
>
> With a good sensor, you can measure half the supply voltage at the
> outputs when no magnetic field is applied. The difference between both
> output terminals goes positive or negative, depending on the field
> direction.
>
> With a bad part, this signal is shifted towards the positve or
> negative direction. Therefore its zero crossing is not at the point
> where the controller expects it, which makes the signal unreadable.
>
> A drive with one faulty sensor will spin when started manually,
> otherwise it will do nothing or oscillate. With two broken sensor, the
> motor cannot operate at all.
>
> Up to now I did not find suitable replacements for the passive hall
> sensors used in the 400k drives.
>
> Patrick

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