Needed: 1 IBM 8" alignment disk.

From: Richard Erlacher <>
Date: Mon Nov 29 19:59:14 1999

I'd be really interested in how you'd make your own alignment diskette.
Could you shed some light here? If this were in any sense straightforward,
I'd have made my own long ago. I suppose I could fiddle with one of my
PerSci drives, causing the head positioner to move as it would have to in
order to produce the famous "cat's-eye" pattern on track 38, but I believe
one would have to build special electronics to generate the sync reference
burst or pulse (depending on whether you prefer DYSAN or SHUGART alignment
diskettes) on tracks 1 and 76. Now, I've got no idea how to make the
azimuthal adjustments precisely enough that I'd trust the results.


-----Original Message-----
From: John B <>
To: Discussion re-collecting of classic computers
Date: Monday, November 29, 1999 6:46 PM
Subject: Re: Needed: 1 IBM 8" alignment disk.

>-----Original Message-----
>From: Richard Erlacher <>
>To: Discussion re-collecting of classic computers
>Date: Monday, November 29, 1999 8:31 PM
>Subject: Re: Needed: 1 IBM 8" alignment disk.
>>Having aligned about 25 8" drives over the last 6 months, I can tell you
>>that if your drive is "eating" your diskettes, the problem isn't with
>>alignment. If it's damaging your diskette emulsion, it's likely that it's
>No.. My "eating" implies I am sticking in original IBM software disks to
>IBM minis and writing over the data on them. :-(
>>either missing the headload pad, or the head penetration is misadjusted.
>>don't know what the procedure for head penetration adjustment on your
>>particular drive is, but most drives seem to require a couple of feeler
>>guages and some glyptol to make sure it doesn't move when you're done.
>>Before I'll consider LENDING anyone one of my no longer readily available
>>alignment diskettes, I want to be dead certain it won't be chewed up as
>>might happen with the misadjusted head penetration or missing headload
>>or written on as might happen with an inappropriately set-up drive or
>>controller. Even a $1k deposit won't ensure I get back a thoroughly
>>diskette, and I've not seen one for sale in over 15 years.
>The *moment* I get this drive up I'll be making IBM alignment disks for the
>>-----Original Message-----
>>From: John B <>
>>To: Discussion re-collecting of classic computers
>>Date: Monday, November 29, 1999 5:38 PM
>>Subject: Needed: 1 IBM 8" alignment disk.
>>>Before I find the highest building to jump off of, I though I might ask
>>>I have a Sykes 7150 8" floppy drive (negibus PDP-8I) that I have invested
>>>half and hour in and have solved *most* of it's problems... It finally
>>>to the PDP and I can select tracks, reset, read status, etc... once in a
>>>while read a sector.
>>>I need a single sided 128 byte record alignment floppy.
>>>When I do a read now, the drive stays busy forever looking for the sector
>>>asked it for. (even if the head is on top of it). Since it was made in
>>>with TTL chips it is only bright enough to sit there and *wait* for the
>>>correct data to come by. An alignment disk would make life a lot easier.
>>>Anyone have one available? Please e-mail.
>>>P.S. The sooner the better.. this thing is eating original IBM software
>>>diskettes from the early '70s
>>>PDP-8 and other rare mini computers
Received on Mon Nov 29 1999 - 19:59:14 GMT

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