RK06 alignment pack

[tony duell]

[Writing alignment disks]
> As far as I know, in special machines mounted on slabs on stone
> weighting tons, standing on dampeners, so that you had absolutely
> vibration free environment, and then a very precisely controlled head
> control system that could write the tracks at the exact place they

I have an idea that some of these units used an optical interferometer to 
determine the head position

> should be. I think the alingment packs even have some tracks
> intentionally offset from true center in order to check signal strength
> when heads are slightly off track as well.

They normally have eccentric tracks so that the signal amplitude varies as
the disk turns. Look at that on a 'scope and adjust for the right bits being
the same amplitude and you're on-track.

> Same kind of equipment was used to actually do the formatting of disks,
> as they cannot be formatted by the disk drives themselves.

While the servo surface can't be re-written in the field (that is what determines 
head positions, after all), I see no reason why the data surfaces can't be 
reformatted on a drive which has a separate servo surface like the RK06/07

On such drives 'head alignment' really means getting the data heads lined up with
(or the right offset from) the servo head.

Incidentally, I once saw a procedure (maybe HP) for rewriting the servo surface of 
a fixed/removeable drive in the field. It used special electronics, but not any special 
mechanics. It went like this :

Mount a good removeable pack
Use the servo surface of that to position the heads (all of them)
Step a track at a time, maybe with deliberate offsets (can be done) and 
write to the servo surface in the fixed disk stack
Now use the rewriten fixed servo surface to position the heads and 
reformat the fixed disk data surfaces.

-tony


        Johnny

>
> /P
>
> On Wed, Jun 17, 2015 at 11:39:25AM -0400, Noel Chiappa wrote:
>> Anyone need an RK06 alignment pack:
>>
>>    http://www.ebay.com/itm/Digital-Equipment-RK06-Aglinment-pack-/221803433215
>>
>> Seems like something that should definitely get saved!
>>
>>      Noel