Re: Apple 400k drive

Sounds like the hall-effect sensors are the problem allright.

>Up to now I did not find suitable replacements for the passive hall
>sensors used in the 400k drives.

If I can identify which ones are faulty, I should be able to come up with one working drive, from the two I have...hopefully!

Terry

• Original Message ----- From: "PSchaefer" <dr.p.schaefer_at_email.domain.hidden> To: "LisaList" <lisalist_at_email.domain.hidden> Sent: Tuesday, March 08, 2011 8:24 PM Subject: Re: Apple 400k drive

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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