30 Jun
30 Jun
3:46 a.m.
June 27, 2020 8:05 PM, "Noel Chiappa via cctalk" <cctalk at
classiccmp.org> wrote:
Looks nice, but the cover, the static filter and the 2 small flatcables with twisted wires
are missing.
Connecting a DZ11 directly to the pcb with the connectors won't work directly as
expected.
7:58 a.m.
On Tue, Jun 30, 2020 at 3:17 PM ed--- via cctalk <cctalk at classiccmp.org> wrote:
June 27, 2020 8:05 PM, "Noel Chiappa via cctalk" <cctalk at
classiccmp.org> wrote:
Looks nice, but the cover, the static filter and the 2 small flatcables with twisted
wires are missing.
Connecting a DZ11 directly to the pcb with the connectors won't work directly as
expected.
Why not? I've linked up DZ11s to the distribution panel PCB with a
straight ribbon cable and had no problems.
The RFI filters effectively swap odd and even pins in the cable (the
pins are straight through the filter but of course you look at them
from opposite sides). That's why the short ribbon
cables between the
filters and the distribution panel are not straight through but
have
crossover connections.. But if you remove both the filter and the
crossover cable it will work as you expect.
-tony
8:22 a.m.
June 30, 2020 4:58 PM, "Tony Duell" <ard.p850ug1 at gmail.com> wrote:
On Tue, Jun 30, 2020 at 3:17 PM ed--- via cctalk
<cctalk at classiccmp.org> wrote:
Ah, I did not know that, interesting to know.
Ed
June 27, 2020 8:05 PM, "Noel Chiappa via
cctalk" <cctalk at classiccmp.org> wrote:
https://www.ebay.com/itm/224058116598
Noel
Looks nice, but the cover, the static filter and the 2 small flatcables with twisted
wires are
missing.
Connecting a DZ11 directly to the pcb with the connectors won't work directly as
expected.
Why not? I've linked up DZ11s to the distribution panel PCB with a
straight ribbon cable and had no problems.
The RFI filters effectively swap odd and even pins in the cable (the
pins are straight through the filter but of course you look at them
from opposite sides). That's why the short ribbon cables between the
filters and the distribution panel are not straight through but have
crossover connections.. But if you remove both the filter and the
crossover cable it will work as you expect.
-tony
9:19 a.m.
On Tue, Jun 30, 2020 at 5:15 PM ed--- via cctalk <cctalk at classiccmp.org> wrote:
Ah, I did not know that, interesting to know.
I suspect the filters were a later addition. The original idea was to
just connect the DZ11 PCB to the distribution PCB with a
straight-through cable. But the filters had to be added to meet some
interference regulations (is that fcc part 15??), the filters swapped
the pins over, hence the special crossover cables between the filters
and the distribution PCB. Had the filters been part of the original
design then either they would have been on the distribution PCB or the
PCBs would have been designed so that all cables were straight (in
which case it would not have worked without the filters.
-tony
Connecting a DZ11 directly to the pcb with the
connectors won't work directly as expected.
Why not? I've linked up DZ11s to the distribution panel PCB with a
straight ribbon cable and had no problems.
The RFI filters effectively swap odd and even pins in the cable (the
pins are straight through the filter but of course you look at them
from opposite sides). That's why the short ribbon cables between the
filters and the distribution panel are not straight through but have
crossover connections.. But if you remove both the filter and the
crossover cable it will work as you expect.
-tony 
9:56 a.m.
On Jun 30, 2020, at 12:19 PM, Tony Duell via cctalk
<cctalk at classiccmp.org> wrote:
On Tue, Jun 30, 2020 at 5:15 PM ed--- via cctalk <cctalk at classiccmp.org> wrote:
Ah, I did not know that, interesting to know.
I suspect the filters were a later addition. The original idea was to
just connect the DZ11 PCB to the distribution PCB with a
straight-through cable. But the filters had to be added to meet some
interference regulations (is that fcc part 15??), the filters swapped
the pins over, hence the special crossover cables between the filters
and the distribution PCB.
That sounds right. Yes, FCC part 15. That arrived somewhere in the middle of the PDP-11
era, so old PDP-11 peripherals and systems don't comply while later ones do.
paul
Connecting a DZ11 directly to the pcb with the
connectors won't work directly as expected.
Why not? I've linked up DZ11s to the distribution panel PCB with a
straight ribbon cable and had no problems.
The RFI filters effectively swap odd and even pins in the cable (the
pins are straight through the filter but of course you look at them
from opposite sides). That's why the short ribbon cables between the
filters and the distribution panel are not straight through but have
crossover connections.. But if you remove both the filter and the
crossover cable it will work as you expect.
-tony
1397
days inactive
1400
days old
5 comments
4 participants
participants (4)
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ard.p850ug1＠gmail.com -
ed＠groenenberg.net -
jnc＠mercury.lcs.mit.edu -
paulkoning＠comcast.net