DEC QBUS Backplanes

[Glen Slick]

On Fri, Apr 17, 2020 at 9:52 AM Bill Gunshannon via cctalk
<cctalk at classiccmp.org> 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
https://www.ebay.com/itm/DEC-QBUS-BACKPLANE-BA123-DEC-54-17507-01-PDP-11-MICROVAX/263251797600
https://i.ebayimg.com/images/g/LygAAOSwrP9Z2V7z/s-l1600.jpg