OT Mitsubishi Monitor Weirdness

From: Mzthompson_at_aol.com <(Mzthompson_at_aol.com)>
Date: Fri Mar 8 22:32:37 2002

On Fri, 8 Mar 2002; Julius Sridhar <vance_at_ikickass.org> wrote:

> Hi people. I have a Mitsubishi Diamond Pro 900u (nowhere near on-topic
> but I figure people here might know better what causes this kind of
> problem). If I provide it with a sync-on-green signal to its BNC
> connectors (It has five, I connect three), the monitor syncs up just fine,
> but all the areas that are black show up with a green cast. The white
> areas show up just fine. I haven't looked at an image with color yet, but
> I would guess that all the colors would probably be shifted towards the
> green. Any ideas?

I use to see this often during my tour as a television studio engineer.
It all came down to one word: TERMINATION. I had forgot to terminate
the video cables going into a monitor, or disconnected the monitor at
the end of a chain.

We all know to terminate the SCSI bus, and the other day there was a
discussion of terminating the floppy cable as part of Dave Jenner's
thread on multiple floppies. We also need to remember that any time
you run a signal down any wire from point A to point B, it needs to
be terminated in its characteristic impedance. If it isn't, some
bad things can happen. As an example, I use to work on some
navigational transmitters with power output of a few hundred watts.
There was a test jack for sampling the RF output and you hooked
a scope to the jack. The gotcha was when you hooked the coax cable to
the transmitter first instead of the scope. If you did that, the
transmitter went down within seconds. The open circuit at the other
end of the coax got reflected back to the transmitter as a low
impedance and detuned it, and the monitoring circuits would detect
the detuning and pull the plug.

On the back of my Mitsubishi Diamond Pro 20 there is a switch next
to each BNC, used to terminate each input. If the monitor does not
provide terminate switches, you can always try BNC T connectors
and 75 ohm terminators.

In a later message, Julius Sridhar <vance_at_ikickass.org> also wrote:

> Never mind. The Clamp pulse setting was in the wrong position.

I am curious to know if your monitor has termination switches. If
so, how about setting the clamp pulse back to what it was and then
terminating the inputs. If not, do you have the T's and terminators
to try it that way. I would be interested to know the results.

Mike
Received on Fri Mar 08 2002 - 22:32:37 GMT