Symbolics rescue (RK03/Diablo Type ?31?)

From: Peter C. Wallace <>
Date: Sat Mar 2 21:27:07 2002

On Sat, 2 Mar 2002, Tony Duell wrote:

> >
> If tghey are Diablo 31s....
> > > For nostalgic reasons, I have wanted to acquire two particular disk drives
> > > for a PDP-11 of mine... I don't remember what they are called or what brand.
> > > But - there are two of them in the very far right of the symbolics rescue
> > > picture at the top of the rack with light brown trim line across the front.
> > > Can anyone tell me what those are - and if there are any around to be
> > > obtained? How hard are they to work on? Is the positioner based on patterns
> > > on the drive or a glass reticule?
> The positioner does not depend on any servo patterns on the disk surface
> (so it's like an RK05 -- in fact it uses the same media). The position
> reference is a 'transformer' made from PCB tracks mounted on top of the
> positioner mechanism. One PCB contains the 'primary' and it rotates
> relative to the other which contains a pair of 'secondaries. The output
> signals are pretty similar to those from the optical transducer in the
> RK05, actually.
> The positioner itself is a permanent magnet DC motor (!) -- with carbon
> brushes. I have no idea how they got it to work, but it does work. The
> spindle motor is another permanent magnet DC motor, directly driving the
> disk spindle.

        The spindle motor has a funny speed control where about 90% of the
voltage needed to run at full speed is appled through a power resistor. A
digital circuit decides if the speed is to low and shorts out the resistor. I
think they got 1% speed control with that simple circuit - of course the
spindle has a lot of inertia...
        Other funny thing is I think the power supply for the drive is the
same as a Hytype I power supply. The Hytypes use the same encoder as the
drives head positioner... (as did the Singer model 40 disk drive where the
Diablo design presumable came from)

> The electronics is half a dozen plug-in cards in a backplane which can be
> pulled up for access. It's not hard to work on, and the components are
> all standard IIRC. I have (somewhere) the service manual. The PSU is
> external (+/- 15V IIRC).
> > IIRC they're RK03's aka Diablo type 31?
> >
> > You must have an RK11-C controller...
> Or make a drive select line decoder (a couple of chips IIRC) for the
> RK11-D. Those actaully existed commercially in the UK -- Plessey sold
> them to use Diablo drives (and similar units) with the RK11-D or their
> clone of same.
> -tony

Peter Wallace
Received on Sat Mar 02 2002 - 21:27:07 GMT

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