Your description sounds like the cabinet has already been hacked by a prior
owner to remove a key component. And you're saying that the rear
cross-piece is present but both of the top cross-pieces are absent?
Completely weird. I'll contact you off-list and we can exchange photos to
From: Chris Elmquist <chrise at pobox.com>
Sent: Tuesday, March 1, 2022 5:21 PM
To: pbirkel at gmail.com
Cc: 'General Discussion: On-Topic and Off-Topic Posts'
<cctalk at classiccmp.org>
Subject: Re: DEC top-mount corporate cabinet
Thanks very much Paul and others. The overview you linked is very helpful
as I now have the actual model number for the rack that I have.
It is indeed the H9642-AD 40" "Top Loader" but it is missing whatever
piece goes behind the H9544 DA Bezel (#4) shown in the component parts
My mystery is what that cross piece behind the bezel looks like, how it
attaches to the vertical rails of the rack on each side and then how the
bezel attaches to the cross piece.
The back of the bezel has a ribbed channel that looks like some kind of
bolts or other threaded or inserted fasteners were screwed or snapped into
this channel and those were attached to the cross piece somehow.
That's my missing link ...
I fabricated an aluminum bar cross piece and then used heavy duty hook and
loop-like fasteners to attach the bezel to this aluminum bar but it's cheesy
and loose. I'd like to someday find the proper solution.
On Tuesday (03/01/2022 at 03:23AM -0500), pbirkel at gmail.com
The traditional DEC racks/cabinets are either full-height ("standard"
H960) and part-height ("short" = H967) 19" racks. These are welded
steel frames built for computer-room type environments. When DEC
started selling into office environments (think data processing /
business operations) they designed a new line of cabinetry that was
intended to fit into an office where sight-lines are important and the
desire was to look/work more like other types of office equipment.
The PDP-11/60 was I think an early example of the redesigned cabinets
-- really a double-wide plus a bit, but of more modest height (roughly
that of the H967). After that you see single-width cabinets holding
just 18U like the one that you have -- capable of holding a complete,
but modest, system. These newer-style cabinets/racks are riveted,
rather than welded. Emphasis was on style, cost-effectiveness, and RF
given the need to operate near other types of office equipment.
Here's a good overview:
On the left side of page 8-of-16 you'll see a description of the 40"
Medium Systems Series, including diagrams and pictures of the "top-loader"
(H9642-AD) and "front-loader" (H9642-CA) designs. There isn't any
to go from one to the other. It would be possible to
get a functional
top-loader out of a front-loader with some metal reworking.
Basically, remove the lid and then (in effect) move the cross-pieces
down 6U and add what amount to four gusset plates for lateral bracing.
In the H9642-AD photo you can see the plates on the rear cross-piece.
The front is similar, but sensitive to ensuring that the center 6U
isn't significantly occluded; the front cross-piece may require some
modification. There are a few other changes but moving the
cross-pieces down are the key. Notice the H9544 CA Trim Kit,
RL01/RL02 -- these are plastic pieces that bridge the gap between the
HDD cover and the cabinet side-panels; nice to have but they're mostly
If you decide to attempt (or simply want to gauge the complexity of) a
conversion I can see about getting some close-up photos of the various
components and connections. A conversion would not be a simple task.
While the brochure speaks of "purchase as component kits" and the
table simply states "Basic Frame Kit", it's not the *same* frame kit
for -AD and -CA, and I suspect that "kit" in this case was not an IKEA
flat-box of parts but rather a factory-assembled frame to which one
added other components as appropriate for the intended use. These frames
Notice that H9542-AD is distinct from the H9542-CA
(Note that the TU80 -- http://gunkies.org/w/images/5/52/Tu80.jpg
basically a H9642-AD "top-loader" with a hinged lid and