Re: Apple 400k drive

Did I say 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"

I meant of course, the hall-effect devices in the MOTOR(i.e. spindle) , not the motor controller IC.

Terry

• Original Message ----- From: "Terry Stewart" <terry_at_email.domain.hidden> To: <lisalist_at_email.domain.hidden> Sent: Tuesday, March 08, 2011 9:18 AM Subject: Re: Apple 400k drive

> Hi Guys,
>
> This is the issue with my 400k Lisa drives Phil alluded to. Actually
> there are TWO malfunctioning drives and they show the same symptom.
>
> Often the drive doesn't spin the disk on either insertion or activation
> through a mouse click via the GUI. Whether or not the drive is activated
> depends on the exact position of the spindle. If you manually turn the
> spindle a little, it will activate. If the spindle stops on a "dead spot"
> it won't turn the next time the disk is inserted or activated. If I'm
> lucky enough to insert the disk and have it spin first time, one of the
> drives will load software but only very slowly and not always. I'm sure
> there are a lot of read-retrys going on. The second drive doesn't load
> software at all even if it does spin. There may be other issues with this
> one.
>
> 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. The evidence for this is as follows...
>
> I measured the voltages on the TA7259 pins when the drive under the
> following two states, manually pushing down the disk-detection lever to
> simulate a drive being inserted....
>
> 1. detector switch pressed and spindle starts to spin (this is what SHOULD
> happen)
> 2. detector switch pressed and the spindle does not move at all
>
> What seemed to differ between 1 (spin) and 2 (no spin) was pin 6 (c-phase
> drive output terminal), pin 7 (b-phase drive output terminal) and pin 9 (a
> phase drive output terminal). Where the motor refused to turn with the
> switch on, these values were almost zero (with switch on or off). When
> the motor DID turn on switch on these were around 12v (again either with
> the switch on and off).
>
> There is more. If I measured the voltage (switch off) and slowly rotated
> the wheel manually values on the three pins stayed mainly at 12v. but
> occasionally dropped to zero for a few degrees of turn, then quickly back
> to 12 as I rotated. In a 360 deg rotation, there were four of these
> "dead" (0V) areas at right angles to each other (approx 3, 6, 9 and 12
> oclock). Whenever the wheel was positioned so the voltage was zero on
> these pins,
> switching the drive on (depressing the drive detect lever) had no effect.
> When it was 12v, the motor sprang into life when the disk detect switch
> was pressed.
>
> I figure the reason that the disk keeps spining if it happens to start up
> is the momentum keeps it going over the dead spots. It's not good for
> keeping the proper speed though, which is why software loading takes so
> long.
>
> I've replaced the TA7259 and associated caps with no improvement. Major
> suspicion is on one of the hall-effect devices. The next step is to see
> if I can identify which hall-effect devices are faulty and which are ok
> from both drives, and cobble together one drive with known good
> hall-effect devices.
>
> That is the theory, and that is where I'm up to. If you think I'm on the
> wrong track, please say so. I'd be interested to know if anyone else has
> come across this symptom (and what you did about it). It's a coincidence
> that two out of the three drives I have are afflicted with this.
>
> Cheers
>
> Terry (Tez)
>
>
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