27 Jul
2011
27 Jul
'11
1:55 p.m.
On 27/07/2011 12:14, Jochen Kunz wrote:
Not necessarily, I do it all the time. And the lack of a local ground
is almost certainly where all that hum and noise is from.
On Wed, 27 Jul 2011 11:31:34 +0200 (CEST)
Christian Corti <cc at informatik.uni-stuttgart.de> wrote:
How did you
connect your scope? Looks more like a ground problem with your
measurement setup.
This could be the problem. I don't have an isolating
transformer. GND
of the scope and GND of the PDP-11 are connected to earth of the mains
plug. Because of this I connected both to the same power strip. I did
_not_ connect the GND clip of the probe to GND of the PDP-11. If I had
done this, I would have created a ground loop. This, of course, _will_
create problems. But if the M930 is enough and if the voltages are OK,
why can't I halt
the CPU with the control panel? There are NPR jumpers in the backplane
and grand cards in emty slots.
Classic sign of something wrong with the bus grants. If the grant cards
are all the small type, are they the right way round? Is there one in
every slot, including the last (slot 9)?
--
Pete Peter Turnbull
Network Manager
University of York