Re: Apple Drive 5,25"

[mjmahon@aol.com (Michael J. Mahon)]

Giorgio Morocutti wrote:

>On 18 Nov 2002 21:17:24 GMT, mjmahon@aol.com (Michael J. Mahon) wrote:
>
>>Giorgio Morocutti wrote:
>>
>>>>I don't have anything specifically on these drives, but would
>>>>be very surprised if they were materially different from the
>>>>Disk ][.
>>>
>>>Unfortunately they are totally different :-(((((
>>
>>That's very interesting.  Could you elaborate on the differences?
>>Analog card?  Drive?
>>
>The mechanical part is ALPS, and there is a step-by-step motor for
>read/write head (no old cam) and the electronic part have one custom
>chip more then chips 74LSxx  standard

Interesting--I didn't know that Apple had ever made any drives
like this.

The band-drive head is not an issue, since the control of the motor
is identical to the Shugart stepper/cam arrangement.

The custom chip is a much bigger problem.  I have several half-height
drives that are disabled because someone inadvertently plugged the
drive into the interface card backwards at some point in the past,
blowing the custom chip--which contains essentially all the drive
logic.

I have never found a replacement for these chips.  The logic is
not complex--a PAL could easily hold it--but I've never finished
the reverse-engineering needed to do it.

>>And in what way are the drives broken?  No operation at all?
>>No seek? No read? No write? Mechanical issues?
>
>The motor turns, but no read, no write.

This symptom sounds very much like the symptom of my
"blown" drives.  ;-(

>Ciao
>(sorry for my bad english ! )

Not at all--your English is fine!

-michael

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