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
shielding 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
there for style.
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 are _seriously_ riveted.
Notice that H9542-AD is distinct from the H9542-CA "component kit".
(Note that the TU80 -- http://gunkies.org/w/images/5/52/Tu80.jpg
basically a H9642-AD "top-loader" with a hinged lid and special-purpose 13U
From: Chris Elmquist <chrise at pobox.com>
Sent: Monday, February 28, 2022 2:08 PM
To: pbirkel at gmail.com
; General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: DEC top-mount corporate cabinet
On Saturday (02/26/2022 at 03:21PM -0500), pbirkel--- via cctalk wrote:
A top-mount corporate cabinet looks like this:
front-bar in the photo is over the 1U strengthener that braces the
upper portion of the rack ... since there is no brace at the top (as yours
Your cabinet will work fine; in my experience
RL02's are always tight
and fiddly any place but the top-spot.
Is there a (hand-)book that describes the DEC cabinets and in particular
this "top-mount corporate cabinet"? Is there a BA # for this cabinet?
I have an 11/34 in said cabinet but it is missing this 1U strengthener
although I do have the 1U front-bar. I had to jigger a means to hold the
front-bar in place and have been unable to understand how it would correctly
attach to the rack and the strengthener, probably because I don't have the
Any part numbers or drawings that show this arrangement would be quite