Panasonic JA751 8" drive question

Steven Hirsch snhirsch at
Sun Nov 1 15:11:13 CST 2009

On Sun, 1 Nov 2009, Fred Cisin wrote:

> On Sun, 1 Nov 2009, Tony Duell wrote:
>> It's up to you. I'd problaby trace out the scheamtics to see just what
>> was going on. But to be honest, with that 7812, it's going to need more
>> than 12V, and 24V sounds likely.
> Bizarre speculation:
> Since most 8" drives use 24V, is there a possibility that this is a 5v&12V
> drive design, with the 7812 there to adapt it to 24V?
> Is there ANYTHING on the drive connected to that pin of the connector that
> does NOT go through the 7812?  If not, could you feed it relatively clean
> 12V downstream from the 7812?

Yes. From what I can tell, power to the head-load and door-lock solenoids 
is picked off directly from the +24V input.  Looks like the motor PCB is 
on the far side of the +12V regulator (uses a "pancake" style direct-drive 
motor with a little speed-control board next to it).

Seems to work fine on 24V, which is a relief.  This was a brand, spanking 
new drive that came sealed in the anti-static bag.  With a 1986 
manufacturing date, it's the newest such unit in my collection.

Last hurdle is to figure out if I can setup to have the motor run only on 
select.  There are a few jumpers, but nothing obviously labeled for this 
purpose.  As it is, the motor starts as soon as the diskette is inserted 
and breaks a photo-sensor - doesn't even need the latch closed.  I'd be 
very surprised if there wasn't a way to change this behavior, but without 
documentation it may take some playing around.



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