Re: Just got a possible prototype Widget disk - any special considerations?

Am Montag, 29. Dezember 2014 20:25:00 UTC+1 schrieb compu_85:

> -No apple serial number sticker on the front, instead a 4 digit SN
> is written in pen (my other 2 widgets have 5 digit SNs on an Apple
sticker)

 ...and sometimes the serial number is stamped onto the chassis.

> -The Read/Write and Servo boards are different part numbers than
> my other 2 drives

There are two PCB designs with different part numbers, and each comes with at least five revisions (marked from A..Z). Also for the controller -- the old one is a small four-layer board, the new one a bigger two-layer design.  

> -The MotherBoard has green edge connectors vs. the black on
> my other 2 drives

...and some have blue connectors. The same applies to the stopmask of the bareboard: there are many colors between yellow an green.  

> -The heatsink on the Servo board was trimmed

That is unusual and might be an indication that someone repaired the drive and needed access to the servo board. Replace it with something bigger if you want to operate the drive for a longer time. The servo driver transistors do get hot.

> I was going to pop in the controller from one of my other drives and see
what
> happens. However, if there is anything "interesting" on the drive I don't
want to
> risk damaging / erasing it. Are there any special steps I should take?

Before powering up, shake it carefully and listen for loose parts inside. There is a glass scale inside, a part of the servo system. This is glued to the chassis frame. The glue ages, and if the drive is bumped, it may come loose. If this part gets into the motor, the whole inside of the drive is turned into dust. Unfortunately a very common failure mode.

As the next step, rotate the motor flywheel carefully. If it rotates without any irregularities, apply power. After some 30 seconds, you should hear a clicking noise, followed with a "squeak-squeak". If not, turn it off and check and adjust the brake solenoid on the bottom. Put the drive upside down, so that the heads do not move the heads while the drive is not spinning.

After the initial "squeak-squeak", the controller board performs a self test, then a RW test on a spare track, and finally a surface scan. If everything passes and the green light stays on, you can use BLU to create an image file. Else, swap boards to identify the faulty one.

Do not touch the adjustment screws on the motherboard unless you know what to do. Do not bend the motherboard or lift the drive using it as a handle -- this may misalign the pots. Do not swap motherboards, this will not work without realignment. And never never never open the drive (unless you are sure that it is scrap).

If you know what to do: circuit diagrams and alignment instructions are on bitsavers.org.

Patrick

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