DEC top-mount corporate cabinet

pbirkel at pbirkel at
Tue Mar 1 02:23:26 CST 2022


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 "mod-kit"
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 -- -- is
basically a H9642-AD "top-loader" with a hinged lid and special-purpose 13U

-----Original Message-----
From: Chris Elmquist <chrise at> 
Sent: Monday, February 28, 2022 2:08 PM
To: pbirkel at; General Discussion: On-Topic and Off-Topic Posts
<cctalk at>
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:
>  The "DECDatasystem"
> 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


Chris Elmquist

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