Bad DMX Port, or the Evil of Non-Termination?

[Chris Chapman]

You may have seen my other post about problems getting some Elation EPAR QA's running on my ION. Here is the tale of troubleshooting, and you be the judge on what the real problem in this setup is:

There are 10 VIVID-R's that are running off of Universe 2. #10 in the series is NOT terminated. This is a Net1 facility with limited Universe 2 ports at FOH, and in galleries SL & SR. The port in question (see below) is in the SL loading gallery.

Taking a separate drop off of Universe 2, a stand alone EPAR acts flaky when connected. Strobes, randomly flashes, does not respond to intensity or hue/sat commands.

Same instrument, when plugged directly into the Universe 2 port on the back of the ION (skipping the network) works fine with a "compatible" profile (OPTI PAR QA) in all modes.

Bring all 10 EPARS up with correct addressing, and profile. Unresponsive, and random flashes/colors happen.

Swap out 3pin/5pin DMX adapter to see if that is the problem. Problem persists.
Swap out DMX cable from wall port. Problem persists.
Take the DMX drop from the last VIVID/R in series (that was unterminated) and problem goes away.

So what do you think? DMX reflection due to no-termination? Or bad port? On the, "Gee, should have thought of that" line is that this port is where we used to plug our DMX projector dowser into. Last year (right after we got our VIVID's) the Dowser started to act flaky on the DMX network. I thought it was a bad port on the dowser. Next step is to put the dowser inline and see if it's troubles are magically cured as well.

What nuttiness have you seen on your DMX network that can be attributed to non-termination?

 

[DavidNorth]

So let me see if I understand correctly.

The 10 Vivid-Rs work correctly from Port 2 of the 2 Port Node but the EPARs, no matter whether they are direct from Port2 or into the pass through of the last Vivid-R that is in Port 2, and in any quantity, including one, do not work correctly.

The Vivid-Rs always work no matter how things are wired into Port 2.

The EPARs are fine connected to the Ion.

The dowser used to work fine on Port 2 then atarting having troubles when the dowser and the Vivid-Rs were on the same port together????

Has there been any reconfiguration of the Node? I ask, because it sounds almost like there is an incompatibility with the DMX speed that the Node is sending. There could also be a ground loop in the data wiring. Have you tried plugging into Port 1 and seeing what happens there?

I do not think this is due to lack of termination, although if you can place one at the end of the line, it would be nice to rule this out as well.

David

 

[Chris Chapman]

So let me see if I understand correctly.

The 10 Vivid-Rs work correctly from Port 2 of the 2 Port Node but the EPARs, no matter whether they are direct from Port2 or into the pass through of the last Vivid-R that is in Port 2, and in any quantity, including one, do not work correctly.

The Vivid-Rs always work no matter how things are wired into Port 2.

The EPARs are fine connected to the Ion.

The dowser used to work fine on Port 2 then atarting having troubles when the dowser and the Vivid-Rs were on the same port together????

Has there been any reconfiguration of the Node? I ask, because it sounds almost like there is an incompatibility with the DMX speed that the Node is sending. There could also be a ground loop in the data wiring. Have you tried plugging into Port 1 and seeing what happens there?

I do not think this is due to lack of termination, although if you can place one at the end of the line, it would be nice to rule this out as well.

David

Vivid-R's work reliably from a different port 2 100% of the time. The EPARS ONLY work when run off of the last VIVID-R in series. I have not tried pulling the Vivid-s feed and running independanty of them.

EPARS are fine coming right off the board as well.

Dowser started having problems on Port 2 when the VIVIDs came online. This may be coincidental though.

There has been no reconfiguration of any nodes.

Because of the way the space was wired there are, get this, no other Port 1's anywhere but in the booth (for control) and dimmer racks. There are Port 1/2 ins and outs for an old RNC position onstage, but they are used as a loop through to racks and distro. It's a funky RNC based design circa '97, and the RNC was pulled from the loop about 6 years ago due to a power spike.

Before getting the VIVID's, there would only occasionally be one DMX device live in Universe 2. The dowser, or occasionally a fogger or rental strobe.

Using the OPTI-PAR QA profile works for me. I might test the EPAR QW which is in the library, but seems to have a channel mismatch between how the QA & QW are set up by Elation. I noted that the Opti-Par Color Mixing labeling is off in the LCD screen when I scroll through on the encoder. But I think these results are expected when using an Amber instead of a White LED.

 

[Flyboy]

I think there is a little language confusion, so can I please clarify:

You said that you have "Universe 2 ports" in the Stage Left and Stage Right Galleries. For clarity I am going to refer to these as U2-SL (for the Port in the SL Gallery) and U2-SR (for the Port in the SR Gallery). It sounds like these are both One Port Gateways which are configured to output Universe 2 - is this correct? And am I correct that in your previous comment, when you referred to "Port 2" you were referring to one of the "Universe 2 Gateways?" Also, where are the Vivid-R's getting their DMX from? U2-SR or from U2-SL?

First of all, I would definitely terminate the line. Even though that probably isn't the issue (since they work fine when in line with the Vivid-R's), we can't rule it out until it's been tested. If that doesn't clear it up, I would say that it sounds like it is a problem with the U2-SL gateway. Assuming that the Vivid-R's are plugged into the U2-SR gateway, it would make sense that fixtures in line with them would also behave. Have you tried running the Vivid-R's from the U2-SL gateway? If they also have problems, then we know it's an issue with the Gateway Node.

 

[sk8rsdad]

The Desire line has self-terminating DMX. So if it is the last thing on the chain it is terminating the DMX. If not, you should have a terminator.

 

[derekleffew]

The Desire line has self-terminating DMX. ...

Lest we open the same can o' worms again, let's use "auto-terminating receptacles" or similar, rather than "self-terminating DMX."

But it does seem a plausible explanation to the issue in question. Put a Desire fixture at the end of the line and see what happens.
EDIT: Wait; the OP is talking about Vivid-R's, not Desires. I don't think any (pre-Desire) Selador ever used the auto-connectors.