Re: Just got a possible prototype Widget disk - any special considerations? from PSchaefer on 2014-12-31 (lisalist1)

From: PSchaefer <dr.p.schaefer_at_email.domain.hidden>
Date: Wed, 31 Dec 2014 08:52:29 -0800 (PST)

Am Dienstag, 30. Dezember 2014 20:21:29 UTC+1 schrieb compu_85:

>
https://lh5.googleusercontent.com/-V4qbUsfa-UA/VKH8-Z9ysEI/AAAAAAAAF0o/ly3O9bKFnBY/s800/IMG_20141229_200128.jpg

At least your servo board is one of the oldest made. The first PCB layout, and revision -A. I don't know if this is a prototype or if these also have been shipped to customers. All my Wigets look like they got a lot of manual tweaking after manufacturing, so it seems to me that Apple shipped only "prototypes" before they cancelled this product line.

> Upon powering it up it spins fine, unlocks the head brake, does the
initial
> squeak squeak then seems to get stuck doing the same operation over and
> over. From your notes this would be the r-w test on the spares track.

It seems to me that the initial squeak-squeak (data recal) is repeated over and over, so I would check the servo board first.

If you have access to an oscilloscope: connect it to TP9 and TP8 on the servo board and set to X-Y mode. An old analog scope does this better than the modern digitizers. During the recal attempts you should see a circle with a diameter of approximately 5 volt. If it looks more like an egg or is significantly too small, your mainboard is misaligned or there is a fault in the HDA or mainboard. If the circle looks good, replace your servo board.

If the lissajous circle looks good and recal fails even with a known-good servo board, you can try to reduce the servo gain. This is the lowest one of the triple pot on the edge of the motherboard. Mark the old position (take a photo) and change the setting carefully. With too much gain, the heads will bang into their endstops, with too little gain the seek will timeout before settle. Apple recommends 35ms for 60 tracks, but with rotten mechanics a slower value (like 40ms) works better.

I do not know if BLU allows you to read the fault memory of the controller board. This will give you additional information which step of the selftest failed.

Formatting will not be possible until all tests pass. But you want to get the data from the disks, don't you? So I would try everything else first.

Regards
Patrick

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Received on 2014-12-31 13:33:16