Jumping Intensity in ParCans...

[tabithakeeling13]

So, I mostly work with concerts and such in our big performance hall. Its a church thats been retrofitted into a theatre. I have about 30 Par64s hung in there. Recently, I've noticed that some of my instruments aren't fading on, they jump to full at about 60% intensity. Its really annoying. I think I must have skipped that day in my Tech 101 class. I'm sure its a common problem, but I have no idea what the cause is. Any Ideas?

 

[gafftapegreenia]

Well its not the PAR cans themselves. It could either be:the dimmers, the controller, or the DMX cables.

1) The DMX rate from the controller might be faster than the dimmers can read.
2) The cable connectors might be flaky or it might be mic cable instead of real DMX cables.
3) The faders in the controller might be going bad.
4) and more!

To start, what model dimmers and what model board?

 

[cpf]

LED or conventional?
What kind of dimmers?
What kind of controller?

 

[tabithakeeling13]

LED or conventional?
What kind of dimmers?
What kind of controller?

They're all Conventional instruments, no DMX cables. Its a mix of Twist Lock and Stage pin connectors depending on location (we've got a pieced-together system). The Dimmer packs are all Electrol. I don't know much about them, honestly. You have to switch each dimmer on manually, and our board is a ETC Expression 24/48.
I've redone all the connectors myself, so I can go through and check those first. Our light board seems to work just fine in our black box venue so I feel good in assuming that its dimmer or cable issues.
Ah, troubleshooting, gotta love it...

 

[Les]

The three places I'd check for issues first would be:

1.) DMX run between the console and the dimmers (this one is less likely, as issues with this cable tend to be intermittent [randomly flashing lights, etc], but it is also one of the more accessible things to check. Try running a different cable and see if the problem continues.
2.) Anything having to do with a protocol converter (if one exists in your system).
3.) The dimmers themselves. I'm thinking this is the most likely issue. Now, comes the fun of playing investigator and ruling things out.

Is there any particular pattern to this problem? Are the dimmers showing any kind of overtemp event? Are they the same instruments acting up every time, or does the problem "move around"? Are they on the same pack or in adjacent channels within a pack or rack? What else do these fixtures have in common? I'm assuming that the system has worked fine for quite some time -- has anything changed/moved around recently, other than the console? Any power surges reported in the building lately?
I doubt it's a problem with the 120v wiring leading from the dimmers to the fixtures (as this problem would also surface as intermittent flashing, tripped breakers, etc).

There is also the slight possibility that somehow your console's dimmer curves have been changed for those channels (assuming that it is a predictable, repeatable problem).

 

[gafftapegreenia]

How old are Electrol dimmers? I have no idea but I know on the older dimmers the triacs go bad and can cause this jumping problem to occur. It happened on the KlieglPac 9's at my University.

 

[venuetech]

try exercising the pots/ faders.
a layer oxidation within the pots may have built up. running the faders up and down a large number of times may help.
this may not be the problem but it is quick to try.

 

[Les]

try exercising the pots/ faders.
a layer oxidation within the pots may have built up. running the faders up and down a large number of times may help.
this may not be the problem but it is quick to try.

On a similar note, select the channels on the board and run them up/down [-]using the level encoder wheel[/-], or program them in to a different sub to see if the problem persists.

Sorry, I read Expression and thought you were working with a board with encoders. Looks like you may actually have the Express 24/48. Even so, you can program the fixtures to subs to isolate issues with the sliders.

 

[65535]

Does the Express show a smooth increase in intensity for the channels that are acting up?

Could be a bad dimmer or a bad dmx de-multiplexer sending out bad analog to the dimmer modules.

 

[church]

Does the Express show a smooth increase in intensity for the channels that are acting up?

Could be a bad dimmer or a bad dmx de-multiplexer sending out bad analog to the dimmer modules.

it is most likely the "trim" adjustment on the dimmers on older dimmers the trim points are an analogue adjustment which drifts with time - checking and adjusting these settings is part of the preventative maintenance. On some dimmers they can be adjusted externally others require removal of the covers. Even if the potentiometers used to make the trim adjustments are worn they are an easy fix.

You need someone locally who looks after dimmers to do a service and clean. Many people learned how to do this first level of checks themselves after someone showed them how, but with digital phase control using programmable integrated circuits this adjustment is no longer required.

 

[tabithakeeling13]

Does the Express show a smooth increase in intensity for the channels that are acting up?

They don't. As I move the fader up, the intensity stays at 0% until i've reached around 80 and then it jumps to full and stays there. I get a kind of mid intensity, where the lights flicker, on some of them, but not all.

 

[millamber]

Try it by typing in the channels.

try this: S1 (sneak) chan xx @ Full Enter.

Does the channel smoothly move up to full intensity? If so, you may have a bad fader on the board.

 

[chausman]

I would try restoring to a 1-1 patch, if you aren't already. MAKE A BACKUP first, and make sure there isn't any weird things going on with the profile/attributes the console is using.

 

[Clifford]

Definitely sounds like a profile issue if everything else checks out ok. If you open Patch, in the Dimmer column, see if the dimmers that correspond to the problem channels have just a number (like: 1), or if they have two numbers separated by a backslash (like 1/4). The second number is one line below the first. If there is a second number there, note what it is, go to the Setup menu and then to Profiles. Hit S1 and the number of the profile you noted and check to see what kind of curve it is.

 

[tabithakeeling13]

Hit S1 and the number of the profile you noted and check to see what kind of curve it is.

What do you mean by "what kind of curve it is"? lol. this is the basic information i am missing.

 

[avkid6345]

What do you mean by "what kind of curve it is"? lol. this is the basic information i am missing.

On many consoles including the Express, you have the ability to assign different dimming curves to lights. For example:

The typical (Default) curve on the express is a 1:1 ratio. If your channel is at 0%, then the dimmer will be at 0%.

00 05 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 - Channel on Express
00 05 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 - Dimmer output

If channel is 25% then dimmer is 25%, Channel 75% & Dimmer 75%, you get the idea.
You can also set up different curves for example if you wanted your houselights to dim and then stop at 10%, the dimming curve would be set at channel 0% dimmer 10%.

00 05 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 - Channel on Express
10 10 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 - Dimmer output

It's a menu setting in the console. It's called profiles. SEE PAGE 40 in the manual for your console Based on what your saying, this seems to be the culprit. I don't know if I did the explanation justice, but the link and section starting at page 40 in the manual should cover whatever I missed.

 

[avkid6345]

From what it sounds like, Your lights either don't dim from 0-60% until they hit that point, switch on and dim the remaining 60-100% or do they dim from 0-60% and then jump to Full from 60%? Another test you can do... Assuming channels and dimmers are patched the same. Press [DIM] key, then type the number of one of the dimmers that's troublesome and hit AT. Then type a level [0-99] (33 or 75 might be best for your tests) that you haven't seen that dimmer work with. Then hit enter and the dimmer should go into a "dimmer check" where regardless of how it's patched or profiled, be at whatever level you entered. [Clear] ends the dimmer check.

If you don't see results or can't tell, you can also hit [About] [Dim] and then your troublesome dimmer number. A window will pop up on the display with information about the dimmer. Look for profile. From what I understand you would want the profile to read "0 Linear". That would make the light go proportionally to your fader without any jolts or jumps in the curve. If it's anything else other than "0 Linear" post back or consult the manual in the link I provided on how to change profiles. Good Luck!