Analog 24 Channel wiring help

[Simon Medek]

Hello,

I am designing lights for a high school theater play. the system is analog, 24 channels into the lighting control board. i am new to this and i am needing to know which channels control which sockets. i was told that you have to bring up one channel and plug in a light to each socket to find out which ones come on, this cant possibly be true as there has to be a junction box somewhere that splits up the 24 wires into the 100 sockets. is that junction box a thing or am i think wrong? please help me out!

 

[JD]

There is a lot of information we would need in order to help you out on this. Analog only indicates how the control signal is delivered to the dimmer rack. A 24 channel analog board would be connected to the dimmer rack by a 25 or more conductor cable and dimmer expansion would be limited. A digital system, such as DMX, would have a 3 to 5 conductor cable between the board and the rack, and have the possibility of additional equipment being added.

Now, on to your original question- Most theater systems have some logical layout. this can be complicated if a hard patch bay is wired into the rack, or if a soft patch is done in the board or the rack.
I would start by looking at any labels near the connectors. No matter what coding is on them, you may find the same code in several locations and this would be a good indicator that those connectors are on the same dimmer channel. Sometimes a stagger systems is used, sometimes a symmetrical left-right system is used.

So, for starters, let us know the brand and models of the board and dimmers. There may be clues there as to how the system was thought out.

Another technique would be to set several channels at different levels, such as 25%, 50%, 75% and 100% and then checking connectors using a low wattage test lamp (not more than 100 watts, but no less than 75 watts.) That will cut down the running around a lot. As you start to locate circuits, you may find a pattern developing.

 

[Simon Medek]

Ok, i will look today for the dimmers as i cannot seem to find them. Does there have to be a dimmer rack or is there other ways they could have done it? (VERY old system)

 

[JD]

Ok, i will look today for the dimmers as i cannot seem to find them. Does there have to be a dimmer rack or is there other ways they could have done it? (VERY old system)

Very old can be quiet subjective!
Typically, on an older system you would have one location for the dimmers. Some newer systems use distributive dimming where there are several locations, but I would not think that to be true on an analog system due to the nature of the control cable. That location may be a closet, basement, or even loft area. Try to follow the path of the cables from all locations, you will find they head to some central point.

 

[robartsd]

24 dimmers is a fairly small rack - could even be a pack mounted on a wall somewhere.

 

[AudJ]

24 dimmers is a fairly small rack - could even be a pack mounted on a wall somewhere.

Correct, but I have also seen one situation where 24 dimmers WAS a wall.

 

[robartsd]

Correct, but I have also seen one situation where 24 dimmers WAS a wall.

Depends on how old "very old" is. At least they have remote control. (-;

 

[DrPinto]

Pictures would be very helpful to us.

To find the actual dimmers, you can turn on the stage lights and then listen for the fans. The dimmer rack will have cooling fans that run when the system is on. The racks are often located near the stage in a closet or dressing room so that the noise is kept away from the stage. The patch panel (where you can assign what dimmer controls what circuit) is usually located nearby.

 

[JohnD]

Frequently in high schools you can ask the custodial staff.

 

[robartsd]

To find the actual dimmers, you can turn on the stage lights and then listen for the fans. The dimmer rack will have cooling fans that run when the system is on. The racks are often located near the stage in a closet or dressing room so that the noise is kept away from the stage. The patch panel (where you can assign what dimmer controls what circuit) is usually located nearby.

Dimmers are often loudest when set to 30-50% and loaded near capacity.

 

[derekleffew]

Dimmers are often loudest when set to 30-50% and loaded near capacity.

Incorrect on the "loaded near capacity" part.

I hypothesize the loudest dimmer would be a half-loaded dimmer run below 50%.

Adding more load into each dimmer used will also help as forward phase dimmer chokes reach their full risetime rating when at a full load. So maybe you want to double up the loads into dimmers as your first step. I will tell you that running the dimmers very low are not going to help at all and is certain to make the situation worse.

Back when 1000W FELs were the norm, one of the attempted justifications for going to 1.2kw dimmers was that a 2.4K dimmer loaded with 1k was the worst case sonically; I believe for both dimmer noise and lamp sing. Don't know if that is/was true or not; I believe it was someone from Kliegl Bros. who said it. Coincidentally they were one of the few manufacturers making 1.2k dimmers at the time.

 

[JD]

The dimmer rack will have cooling fans that run when the system is on.

Don't bet on that. Many old analog dimmer systems did not have fans (TTI comes to mind.) We have a 50k rack of "Hub Electric" dimmers, not a fan to be found. (Been on 24/7 since 1989)

 

[DrPinto]

Don't bet on that. Many old analog dimmer systems did not have fans (TTI comes to mind.) We have a 50k rack of "Hub Electric" dimmers, not a fan to be found. (Been on 24/7 since 1989)

I stand corrected. I learn something new every day around here...

 

[JD]

Incorrect on the "loaded near capacity" part.

I hypothesize the loudest dimmer would be a half-loaded dimmer run below 50%.

Interesting! It makes sense that settings below 50% produce the harshest waveform and the chokes will cry out the loudest, but the loading point is counter-intuitive. One would think that the mechanical noise is generated by magnetic interaction between the windings, other windings, and any ferrous material used in the assembly. So, logic would say that the more current, the more magnetism, and thus the more noise. Of course, there are plenty of things in this world that are not logical, so I wouldn't be surprised! Still, I'm going to humor myself next time I am doing a job and try that out.
Can't say I ever sat there and listened to the packs in that way!

 

[Jay Ashworth]

Posting a photo of the control board can't hurt at all...

 

[Fountain Of Euph]

Don't bet on that. Many old analog dimmer systems did not have fans (TTI comes to mind.) We have a 50k rack of "Hub Electric" dimmers, not a fan to be found. (Been on 24/7 since 1989)

JD,
Im interested. I have a hub system in my house (just the elecrics now, at one time everything). I thought Hub went out of business in the 70's. Curious, because this can change the timeline of my venue.

 

[JD]

JD,
Im interested. I have a hub system in my house (just the elecrics now, at one time everything). I thought Hub went out of business in the 70's. Curious, because this can change the timeline of my venue.

Since our system was put in in 1989, I suspect there may be something wrong with the timeline. However, what I think happened is that Hub was bought by another company that may have continued using the brand name. As to when they killed off the Hub name, it appears that would have been the early 90s judging by the fact that they were still being put in in 89.
You may want to look for date codes on any of the modules or parts. That should narrow it down.