Dimmer Electricity "bleed"

beescores

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Jan 29, 2019
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Los Angeles, CA
I'm not sure what else to call it but after literal hours of Google I just have no clue. Any tips would be appreciated!
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I have a 6-channel Leprecon LD 360 DMX dimmer pack with 4 fresnels and 2 practicals (normal lamp bulbs) hooked in. They all run correctly and independently on the channels as patched, however if you turn any one of their channels on, all the other 5 lights also go on at a very low glow (1-2% max). The more of the other channels you have on are, the brighter the ambient glow gets (maybe up to 5%). Specifically zeroing out the channels of the "glowing" lights does not change it. It's as if there is electricity "bleeding" into the other fixtures as long as any channel in the pack is up.

Anyone have any experience with a similar issue or any potential solutions?

EDIT: I do realize it may just be a bad pack but since it's a suddenly new issue with this pack I'm hoping it's user error and not something I need to find money to fix cause we don't have any (like everyone haha)
 
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RonHebbard

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Location
Waterdown, ON, CA
I'm not sure what else to call it but after literal hours of Google I just have no clue. Any tips would be appreciated!
--
I have a 6-channel Leprecon LD 360 DMX dimmer pack with 4 fresnels and 2 practicals (normal lamp bulbs) hooked in. They all run correctly and independently on the channels as patched, however if you turn any one of their channels on, all the other 5 lights also go on at a very low glow (1-2% max). The more of the other channels you have on are, the brighter the ambient glow gets (maybe up to 5%). Specifically zeroing out the channels of the "glowing" lights does not change it. It's as if there is electricity "bleeding" into the other fixtures as long as any channel in the pack is up.

Anyone have any experience with a similar issue or any potential solutions?
@beescores Is this dimmer pack the last DMX device on the line controlling it? If it's the last device on the line, is the line terminated either by the pack or with an external DMX terminator??
Toodleoo!
Ron Hebbard
 

RonHebbard

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The DMX is terminated with the pack, it's the last thing in control.
@beescores I gather you mean the pack is the last thing being controlled, presumably it's in the control of your DMX source, board, console, computer program and dongle, whatever. Is your Leprecon pack powered by one or two line cords? If the pack has separate line cords, one for dimmers 1 through 3 and a second line cord for dimmers 4 through 6, check the neutrals of the receptacles powering your pack while the pack is plugged in and under load. Use almost any VOM or DVM to measure from neutral to a known good ground; there should be zero volts between neutral and ground with the dimmers loaded and lit.
Toodleoo!
Ron Hebbard
 
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Les

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Feb 24, 2004
Location
DFW, Tx.
Might be a preheat function (trickles a bit of power so as to avoid thermally stressing the lamps). Some dimmers have a trim pot to control this, but it could be hidden under the case lid or through a vent hole. Usually adjustable via a small flathead screwdriver - just don't poke around or make the adjustment unless the dimmer is unplugged.

The behavior you describe however, isn't how a preheat function should behave, so you should still call Leprecon.
 
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JonCarter

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Meridian, Idaho, US
@RonHebbard "Use almost any VOM or DVM to measure from neutral to a known good ground; there should be zero volts between neutral and ground . . ." Ron, in my experience the only place there is zero measurable voltage between a neutral (grounded conductor) and a ground (grounding conductor) is at the service entrance where they are bonded together. There has always been some slight voltage difference at any other point on circuits with current flowing due to the voltage drop over the grounded conductor of the circuit.
 

RonHebbard

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Waterdown, ON, CA
@RonHebbard "Use almost any VOM or DVM to measure from neutral to a known good ground; there should be zero volts between neutral and ground . . ." Ron, in my experience the only place there is zero measurable voltage between a neutral (grounded conductor) and a ground (grounding conductor) is at the service entrance where they are bonded together. There has always been some slight voltage difference at any other point on circuits with current flowing due to the voltage drop over the grounded conductor of the circuit.
@JonCarter Understood but you see where I'm going with this; granted with a sufficiently sensitive scope meter you can measure minute voltages by waving your test leads in the neighborhood of current carrying conductors. Non-contact voltage sensors are another example. Whip me, beat me, make me write bad cheques. Mia culpa, mia maxima culpa (as my Catholic buddies would say) Forgive me for not applying engineering 101 to every epistle I post here on the Control Booth forum.
With my tail between my legs I'll slink back into my dark little corner. I guess if we want to belabor this further, even your common bonding point is often slightly above the nearest copper water pipe by the impedance of the 10' of wire bonding them. Toodleoo!
Ron Hebbard
 

JimOC_1

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Maryland
Back to what Ron Hebbard said up front. Can you purchase an external DMX terminator and plug it into the pack? They look like a DMX-out plug with no wire attached. These do not need to come from Leprecon, they are fairly generic. (make sure you get a 5-pin for you unit, and not a 3-pin)

USER’S MANUAL
“ For proper operation, it is recommended that the last dimmer in the system includes termination for the DMX signal line. This termination is nothing more than a 120 ohm resistor installed across pins 2 and 3 of the 5 pin XLR. For your convenience, a male 5 pin XLR with such a resistor in place is available as an accessory from your Leprecon dealer.”
 

Butch!

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Under there
I imagine you have the pack in one location and then are running cables out to the fixtures and practicals. You haven't done anything crazy like coiling all the cables together or around a pipe or something like that have you? You can get inductive currents in those situations which will affect the lights in the other cables. I've had more than one service call for 'dimmer problems' which turned out to be caused by poor cabling practices. Best story is the time there was a complaint that three fixtures on a 60' batten were all having dimmer problems. Each one was on its own dimmer with one fixture at one end of the batten, one at center and one at the other end. If one was powered on the other two would glow. If two were turned on the other one would glow brighter than when only one was on. If you played with the levels of the other two you could get a good flicker. They said they had tried plugging the lights into different dimmers and the problem would move to the new dimmers. i flew the batten in and saw that they were using long cables and to take up the slack they had tightly wrapped the cables around the batten 20 or 30 times. This had turned the batten into a giant kind of electromagnet/inductor (engineer insert proper term here) and when one fixture was on the field it created on the batten caused current to flow in the other tightly wrapped cables. With two fixtures on the fields fought each other and could produce flickers.

A quick test would be to unplug everything from the pack and directly plug a couple clip lights or other loads into each dimmer and see if it still happens just to rule out some kind of cabling error.
 

RonHebbard

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Waterdown, ON, CA
Back to what Ron Hebbard said up front. Can you purchase an external DMX terminator and plug it into the pack? They look like a DMX-out plug with no wire attached. These do not need to come from Leprecon, they are fairly generic. (make sure you get a 5-pin for you unit, and not a 3-pin)

USER’S MANUAL
“ For proper operation, it is recommended that the last dimmer in the system includes termination for the DMX signal line. This termination is nothing more than a 120 ohm resistor installed across pins 2 and 3 of the 5 pin XLR. For your convenience, a male 5 pin XLR with such a resistor in place is available as an accessory from your Leprecon dealer.”
@JimOC_1 I understood the OP to say his DMX line was terminated by the last pack in the line. Are you suggesting his model of dimmer pack does not include termination? This was my suspicion as well and why I asked the question.
Toodleoo!
Ron Hebbard
 
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JD

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North Wales PA
Thinking ZVC error. (Zero Voltage Cross Detector) Basically, it sets the point where all the firing circuits take their time cues from. If there is too much noise going into the dimmer from the power line, or as a result of other dimmers in the pack firing, errors can occur that shift the black level causing high idle. Often, this may be a result of too much resistance between the power mains and the dimmer pack. (Think long or under-gauged cable.) Even an exceedingly long line from the service panel to the outlet may cause the problem. To diagnose: Plug the pack directly into a know solid power outlet with no extensions. Plug 100 watt clip lights into each channel and try to duplicate the problem. If you can't, then what is described above could be the problem. If the problem continues, then I would suspect a failing part in the ZVC circuit inside the pack, or the processor in the firing circuits have a problem and it's time to send the pack out for service.
 

Chris Pflieger

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Aug 26, 2016
Location
Indiana
I'm thinking ZC error as well.

In looking at the schematics, this seems the most likely. A DMX-512 error seems the least likely.

Either the building wiring is questionable, or the dimmer trim settings are off. Follow the above advice, and also contact Leprecon - it looks like there's some adjustments that can be made in the dimmer.


I'm assuming this is standard 360DMX, and not the 360DMX-HP model, correct?
 

NateTheRiddler

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Arizona, US
Thinking ZVC error. (Zero Voltage Cross Detector) Basically, it sets the point where all the firing circuits take their time cues from. If there is too much noise going into the dimmer from the power line, or as a result of other dimmers in the pack firing, errors can occur that shift the black level causing high idle. Often, this may be a result of too much resistance between the power mains and the dimmer pack. (Think long or under-gauged cable.) Even an exceedingly long line from the service panel to the outlet may cause the problem. To diagnose: Plug the pack directly into a know solid power outlet with no extensions. Plug 100 watt clip lights into each channel and try to duplicate the problem. If you can't, then what is described above could be the problem. If the problem continues, then I would suspect a failing part in the ZVC circuit inside the pack, or the processor in the firing circuits have a problem and it's time to send the pack out for service.
I’m saving/bookmarking/religiously note taking this. I never knew this was even a thing.
 
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JonCarter

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Meridian, Idaho, US
" To diagnose: Plug the pack directly into a know solid power outlet with no extensions. . . ." Now, how does one FIND a "known solid power Outlet with no extensions."? Finding really clean power in a building full of electronics is MUCH easier said than done without a 59-61 Hz bandpass filter with really steep cutoffs and a BIG ground stake down below the water table.
 

FMEng

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I've been watching the Lighting board here on CB for several years now and it sure looks more like a "Computer Problems and Solutions" board than a "Stage Lighting" board. Comments?
Well, unless you want to go back to autoformer dimmers, there's always a couple of microprocessors involved.
 

RonHebbard

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Location
Waterdown, ON, CA
" To diagnose: Plug the pack directly into a know solid power outlet with no extensions. . . ." Now, how does one FIND a "known solid power Outlet with no extensions."? Finding really clean power in a building full of electronics is MUCH easier said than done without a 59-61 Hz bandpass filter with really steep cutoffs and a BIG ground stake down below the water table.
@JonCarter The "BIG ground stake down below the water table" used to also be known as your incoming cold water pipe though not so much these days with PEX and other non conductive water lines.
Toodleoo!
Ron Hebbard