Needed: 1 IBM 8" alignment disk.

From: John B <>
Date: Mon Nov 29 19:52:15 1999

-----Original Message-----
From: Tony Duell <>
To: Discussion re-collecting of classic computers
Date: Monday, November 29, 1999 9:48 PM
Subject: Re: Needed: 1 IBM 8" alignment disk.

>> I was hoping to use an alignment disk as this drive is filled with TTLs
>Hmmm... As I mentioned in another message, _most_ alignment disks won't
>really help you here. What you want is a 'diagnostic' disk -- one filled
>with valid (and known/simple) data patters -- tracks of sectors of all
>0's or all 1's, things like that.
>Fortunately, such a disk is fairly easy to make if you have any other
>machine with 8" drives. I normally use one of my CP/M boxes for this.
>Then you can conitunally read sectors from the disk. Using a 'scope you
>can see if the read PLL is locking -- is the read clock synchronised to
>the off-disk data. Once you've got that, you use a logic analyser
>(preferably) to look at the data stream and see if (for example) it
>detects address marks correctly (these are quite easy to recognise with a
>little practice.
>> pots... The manual has many test points with pictures using the alignment
>> disk. I have no idea if the IBM system diskettes I have actually have a
>> format on them (betting it)
>My guess is that _any_ disk will do for setting up the PLL. For other
>tests it helps if the data pattern is known and simple.

That's why I wanted one.. The manual actually calls it an alignment disk but
your right.. it's really just a diagnostic disk. I am identifying major
points on the schematics right now so I can quickly go through it with a
scope... (I *really* dislike 8" floppies)

Received on Mon Nov 29 1999 - 19:52:15 GMT

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