A 'good-enough' H960 |d|i|g|i|t|a|l| PDP11 masthead replica

Noel Chiappa jnc at mercury.lcs.mit.edu
Thu Jul 9 07:18:40 CDT 2015

    > From: Steven Malikoff

    > a replica PDP11 masthead panel for the DEC H960 rack.

That would be great! (I'd buy one! Or more!) But how are you going to produce
the plastic housing? I suspect that's going to be harder than the inset
coloured panel.

    > I need some help from the list, if possible - I would like the
    > dimensions of the width and height.

The inset (the coloured part) is 8.45 cm high (it's slightly smaller than the
inset in the plastic housing, by about .5 mm); alas, I don't have a metric
ruler long enough to measure the width directly, but in Imperial it's
3-21/64" by 18-9/16".

I don't have a good way to accurately measure the radius in the corners, but
it seems to be about 8.5 to 9.5 mm.

    > I also would like to know of the outer edge of the masthead is a beige
    > colour, or even silver.

The raised edge around the inset panel is painted a dull silver - like the old
silver paint, but with a touch of grey in it. The edge itself is 4.1mm wide,
according to my calipers.

    > The panel would be the inner bit with the radiused corners, the edges
    > being a seperately cut panel which is in front of the the detailed one.

Not sure I follow this? The entire top unit, including the raised edge around
the coloured inset, is a moderately complex injection moulded plastic piece;
behind the front, it's kind of like a box that's open at the back, and there's
a ridge around the back edge on three sides; the bottom edge is shorter, and
the top edge is extended further back. Finally, there are a couple of internal
tabs where it actually connects to the H960.

If you want an original to copy, TopLine has one for sale on eBay (ignore the
ridiculous price they've got on it, they are very reasonable).

    > I would also like to know how deep the recess is for the front. I
    > suspect the same as the filler panel bezel edge, about 3mm.

4.0 mm by my 0.5 mm ruler.

    > And also the depth of the plastic backing.

You mean, how thick is the plastic in the housing? 2.7 mm in one place, 2.8
mm in another, 2.3 mm in a third?

Interestingly, IYWR, in previous thread we'd mentioned how other people
produced their own insets; one for a terminal server, and one for the LISP
Machine. I looked at my LISP Machine one, which I had assumed was in a
similar housing, but it's not! It does indeed fit on an H960 (the early LISP
Machines were built in H960's), but it's quite different.

It's in an extruded aluminium unit (of constant cross-section), with no end
pieces (although the bottom plate has small squared cut out of the corners);
the extrusion's cross-section is exact a capital 'F', but upside down. There
are little square 'serifs' on the 'back' of the 'F' (the front side, when
installed), and the printed panel fits in between them.

Now that I look at it, it looks very similar to me to some things I seem to
vaguely recall being used on earlier DEC machines (either a PDP-6, or a
KA-10, I don't recall where it looks familar from). It being a more-expensive
aluminium extrusion makes sense; that was back when that sort of thing (along
with lots of lights! :-) was acceptable.


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