[N8VEM: 19712] 8-slot backplane extension to 167mm

[John Coffman]

discussion started as:
RE: [N8VEM: 19706] Re: ECB CPU board w/ Motorola MC68030

now:
Subject: 8-slot backplane extension to 167mm

I have Kicad files, which I will post today, to extend the backplane to
167mm (6.6") from 160mm (6.3"). I have made a major change in
power-ground distribution by using copper zones instead of traces.
Ground is on the top, and power is on the bottom. The holes have large,
unconnected pads (although marked "GND" ???), so mounting hardware (M3)
should have no shorting problems.

The issue of VCC on the bottom took some thought. My thinking is that
all the solder nibs for all the signals are on the bottom, so care
ALWAYS will be taken not to short them to anything metallic. VCC on the
bottom is exactly the same, with the added bonus that it is covered by
the solder mask and is well insulated anyhow.

Ground on the top, insulated by solder mask, has been the usual practice
for some time with N8VEM boards.

I was wondering about eliminating the SPDT on/off switch, but decided
instead to reverse the 4-pin Molex connector. This makes it easy to add
a #18 wire to short input VCC to backplane (switched) VCC in case the
switch is not to be installed.

--John

An 8-slot backplane with the enhancements you have suggested would be great!
Will

Will,
<snip>
The backplane is a problem. The 12-slot, as you have noted, is big.
And it does not fit in the nice USPS Flat Rate box. However, the 8-slot
backplane does, and you have indicated that this is your preference.
Let's take a look at the 8-slot situation, and put our heads together in
a few days. The 8-slotter needs to be revisited. I may be the one to
do it, since I would like to extend it from 160mm to 170mm to give that
one connector adequate clearance.
--John

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