DEC quad board rack
jnc at mercury.lcs.mit.edu
Tue Jan 9 09:35:30 CST 2018
> From: Pontus Pihlgren
> Thank you for sharing Noel.
Well, I thought people might find it useful. Over time,I've made a variety of
shelf designs to hold my boards, searching for something that worked really
well, and I liked this one so much I thought it was worth passing it on.
In fact, I liked it so much that I took the dual rack (next to it in the
picture) which held boards horizontally, and re-built it into one that holds
them vertically, like the quad rack. For the duals, the shelf-shelf spacing
(i.e. bottom of one, to the top of the next) is 5" (i.e. the repeat distance
is 5-3/4", when using 3/4" planks).
> In retrospect are there any measurements you would do differently if you
> did it again?
Nope. I made another quad rack for my workshop upstairs, and built an exact
duplicate of the first one (in the picture). And I made another vertical-type
dual rack, also for upstairs.
About the only thing I'd have changed (had I thought of it in time) was to
make that second dual rack a mixture of dual and quad shelves (which you can
trivially do in this design, unlike the horizontal-format one) as I need more
quad shelves, and have an excess of dual shelves. Oh well!
> E.g. Have you found any boards that need higher clearance to the next?
Well... There are some DEC boards which have a Berg connector on the top edge,
and ones which use the later Berg (the ones with the little latch handles)
sometimes place them too close to the edge.
One example of this is the M7800 (DL11); they _just_ fit in a shelf with the
'proper' 10-1/4" spacing, but I have a couple shelves where, due to variation,
the shelf-shelf distance is only 10-1/8", and M7800's won't go into them. The
M7856 (DL11-W) is the same.
For the dual shelves, the E-Rev of the M5904 (MASSBUS transceiver) places the
top of the latches about 1mm from the edge of the board. (The F Rev has been
re-laid out, to move the connector a but further in.) I guess it would be
possible with very careful cutting to space shelves to hold that, but I
elected not to; the tolerances are so slight, a bit too far, and boards will
come out of slots. And some off-brand QBUS memory puts a resistor a little
over 1mm from the card edge, and those also won't go.
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