ISO: Diablo 30 heads

Jay Jaeger cube1 at
Tue May 12 08:10:29 CDT 2020

On 5/11/2020 11:15 PM, Josh Dersch via cctalk wrote:
> Hi all --
> I'm restoring a Xerox Alto and I started going over the system's Diablo 30
> drive.  The heads are in bad shape; the bottom one is actually missing both
> parts of the erase poles (so the black portion of the head no longer makes
> a "t", it's just a black line).  This means the head (in addition to not
> being able to erase) also won't float due to the head having small cavities
> in them.  The upper head looks a little better but I'd love to find a set
> of upper and lower heads if anyone has spares.
> Then I get to learn how to align these things.
> Thanks!
> - Josh

I don't know if they would be compatible or not, but my inventory lists
Diablo part number 15428, Model 31 / RK03 Carriage + Heads Assembly.
(Perhaps I didn't want to remove the heads themselves).  I suspect that
I got the part number off the assembly itself somewhere - I don't have
record of any illustrated parts breakdown for the diablo drive in my
manual database.

As I seem to have two of these assemblies, you could certainly have one
of them, say for something like shipping plus $25.

I don't know the differences between the model 30 and model 31 - but as
the capacity of the model 31 was apparently twice that of the model 30
(2.5MB vs 1.25MB) - with both being referred to as Series 30, with the
model 30 apparently short-lived production wise.  The Series 30
maintenance manual, on the other hand, lists "Standard" and "HI-Density"
of 12 million bits and 24 millions bits, respectively.

>From what I read of the Alto online, its disk capacity was 2.5MB -
implying the drive is a model 31 / hi density.

I don't remember now if these parts I have were from drives originally
on a DEC or DG system.  If they really were from RK03's, then they would
be the high density flavor.

The box they are in are off-site in my storage unit (but well stored),
and I could retrieve them in a day or so if you are interested, but at
present I don't know if this is the entire assembly shown on page 5-3 of
the maintenance manual, or just a portion.

PS:  I seem to recall a "Curious Marc" YouTube video featuring these
beasties along with the Alto they were part of.


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