LD90 dimmer circuit count

[karl]

A venue where I'm currently looking after the lighting has four Strand LD90 dimmer racks. Each rack appears to be equipped with 24 channels therefore giving a total of 96 channels. There are 84 circuits actually installed thus leaving 12 unaccounted for. These racks were installed long before I got involved so I have no idea why this should be the case.

 

My question is: if there are 24 channels physically present (i.e. 24 circuit breakers on the front and 24 power devices (triacs) visible inside) does that mean there are 24 channels available or is the number constrained by software/firmware/licences?

 

If we can use all 96 I don't understand why a dozen have been left unused - I know a couple of places that extra circuits would be handy around the place.

[gareth]

When I read the first bit of your post, I assumed that one of the racks was 12 x 5k dimmers (a common LD90 configuration) - but then I read on and discovered that all the racks have 24 breakers on the front!

 

If the rack has a full complement of power 'blocks' fitted (which it sounds like yours do) then the capacity to run the full 24 channels is there. I can only assume that the 'missing' 12 circuits weren't installed because of a lack of budget/space/need for the required cabling and outlets.

[henny]

I have see installs one this before where an upgrade of dimmers has ended up with spare channels , what I would sujest is to run the spare channels out to a wall mount socka each side if stage and invest in a few lenths of socka and a pair of spiders , this will allow you to throw out extra feeds as needed per show

[gareth]

Whoah! Don't terminate the cable solely in Socapex - it's a mistake that a lot of venues make, and it's a pain in the ass. By all means put a Soca outlet on there as well, but fit a pair of 15A (or 16A, if that's what the venue uses) outlets for each circuit.

[HobitLight]

It may also be possible that there are independants running from the dimmer rack. Are there independants in the building?

[karl]

When I read the first bit of your post, I assumed that one of the racks was 12 x 5k dimmers (a common LD90 configuration) - but then I read on and discovered that all the racks have 24 breakers on the front!

Yes, each rack has 24 x 2.5k dimmers.

 

I can only assume that the 'missing' 12 circuits weren't installed because of a lack of budget/space/need for the required cabling and outlets.

Yeah, the only thing that crossed my mind was that perhaps the LD90s replaced older dimming facilities that provided 84 channels and they didn't want to mess around with adding (or else couldn't afford) extra circuits.

 

It may also be possible that there are independants running from the dimmer rack. Are there independants in the building?

There are independents but they are operated from switches in the control room.

 

I think I'll have to look into doing something with the extra channels - it seems such a waste not using them.

[HobitLight]

It may also be possible that there are independants running from the dimmer rack. Are there independants in the building?

There are independents but they are operated from switches in the control room.

In a local theatre the are independants on LD90 racks (as well as dimming channels) that are also controlled through a box with switches on aswell as DMX. Try using DMX channels that the channels are likely to be and see if that turns the independants on.

[karl]

In a local theatre the are independants on LD90 racks (as well as dimming channels) that are also controlled through a box with switches on aswell as DMX. Try using DMX channels that the channels are likely to be and see if that turns the independants on.

Sounds odd. I'll check if there are any connections to these apparently spare circuits.

[HobitLight]

I have a feeling this switch controller was a wing of a Galaxy or something. Could this be the case? Are there twelve independants? If it is more then they probably aren't controlled through the LD90.

[gareth]

If you don't know whether the extra 12 circuits are actually connected to anything and you want to find out, then instead of flim-flamming about with DMX inputs and looking for things which may not even happen, why not just pop the front off the rack and see if anything's actually connected?! And if it is, trace the cable and find out what it is!

[Bryson]

Whoah! Don't terminate the cable solely in Socapex - it's a mistake that a lot of venues make, and it's a pain in the ass. By all means put a Soca outlet on there as well, but fit a pair of 15A (or 16A, if that's what the venue uses) outlets for each circuit.

 

 

Agreed! It's a real faff if all you want is one or two circuits! Our floor circuits are exactly like this and it's a pain (and ugly) to have to put a spider on for one circuit.

[karl]

If you don't know whether the extra 12 circuits are actually connected to anything and you want to find out, then instead of flim-flamming about with DMX inputs and looking for things which may not even happen, why not just pop the front off the rack and see if anything's actually connected?! And if it is, trace the cable and find out what it is!

Yep, that's exactly what I plan to do tomorrow. I'm pretty sure they're not currently connected but a quick look will soon confirm it one way or the other.

[danjshelton]

It's not too uncommon for an installer to put in "spare" circuits or more than required due to the configuration of the dimmers (e.g. only available as 24 x 2.5Kw and not 12 x 2.5Kw).

 

One of our local venues (Although currently shut down!) actually has an entire spare LD90 (24 x 2.5Kw), just sitting there on the wall with nothing wired into the outputs of it. Always thought it was such a waste to have an entire dimmer sat there doing not a lot! Although they have more than enough dimmer channels elsewhere so little point in wiring into some floor boxes or another LX bar.

 

Out of interest do you know who did the installation or dimmer upgrade (if that was the case)?

 

Dan

[Kazeja]

When the LD90 powers up, the processor does a quick scan to see what power blocks are fitted. This gets reported as a 3 digit code along with the software version.

 

888 would indicate 3 powerblocks each with 8 dimmers (2K5)

848 would indicate 2 powerblocks with 8 dimmers and a powerblock in the middle with 4 dimmers (5K)

 

So if there is a zero reported, it would indicate that the processor cannot see a powerblock in that position. If a power block is fitted where a zero gets reported then the first place I would look would be the security of the 20 way ribbon cable between the missing (zero) power block and the processor. This obviously needs to be done with the power off.

 

What codes do the LD90s display on power up?

[osal]

just out of interest what the breaker rated at on the main distro? could the spare channels be left as a safety feature because of overall loading? I dunno but might be worth a check.