Re: Apple 400k drive

Hi Helmut,

I'm not sure of the exact part description of the passive hall sensor.

In the first instance, I'm going to try and identify which ones are faulty, and mix and match so that out of two non-working drives I get at least one that behaves as it should.

Terry

• Original Message ----- From: "Diogenes45" <helmut_post_at_email.domain.hidden> To: "LisaList" <lisalist_at_email.domain.hidden> Sent: Tuesday, March 08, 2011 9:48 PM Subject: 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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