DEC QBUS Backplanes

Glen Slick glen.slick at
Fri Apr 17 15:05:42 CDT 2020

On Fri, Apr 17, 2020 at 9:52 AM Bill Gunshannon via cctalk
<cctalk at> wrote:
> I have been sorting thru a bunch of stuff in an effort to
> clean the place up (Aren't we all doing that now with all
> this time on our hands?)  I found a backplane.  It says
> Digital on it but does not  have an H- number.  I also
> don;t find it listed in any  of the lists I can find on
> the web.
> It has 8 A-B slots and 4 C-D slots.  the Four C-D are on
> the bottom half of the backplane.  I am assuming it is
> 18 bit and the C-D were intended for things like the 2
> board RL controller.
> Anybody familiar with this and able to identify it?
> Anybody interested in it?  It should fit in a USPS
> Medium Flat Rate Box.

Sounds similar to a BA123 backplane which has 4 Q22/CD slots and 8
Q22/Q22 slots.

But the BA123 is rather distinctive with a gap then a 13th slot where
the M9058 Signal Distribution Board for the M7555 RQDX3 is installed.

For example BA123 backplane part number 54-17507-01 /  50-17506-01

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