Leprecon lm-850 flashing on crossfade

[adickerson]

Hello, Everyone,

I have a Leprecon lm 850 that I picked up used. When I tried to program some looks with any fade time that's more than 0, during the fade the lights will drop out momentarily, or flicker. It happens both when I use the "go" button, or when I use the manual fader. Does anyone have any idea why this is happening, or if there's a way to fix it that I could try myself?

Some more info is that it does NOT flicker when I fade in and out single channels. For example, if I bring channel 1 to full using the channel 1 fader, its fine. If I record that as cue 1, bring channel 1 to 0, then bring channel 2 to full, it also doesn't flicker. If I record that as cue 2, and set the cue 2 time to 5 seconds, then run the cue from 1 to 2, it flickers (again, that's with the manual crossfader AND with the Go button). Doesn't seem to matter which channels I'm using, or which dimmer pack the channels are on. It does this for all of them. Also, the flickers don't seem to be happening at the same time. In the example I used above, channel 1 and 2 will both flicker, but at different times from each other.

I regularly use a Microvision with the exact same setup, and no flickering happens (so I'm pretty sure its the console, and not a faulty cable or some such)

I initially did a quick clean out of the crossfader, but that didn't seem to do anything

Any thoughts on why this is happening, or what I could possibly do to fix it?

Many thanks for your help...

 

[FatherMurphy]

If it was only happening on the manual crossfader, I'd suspect the fader of going bad. However, since you're also seeing it with the timed fades, I'm suspecting something more at the circuit level, some component going bad in the submaster circuit between the timer and submaster level information, and the rest of the individual channel level information.

I'd suggest calling Leprecon at (888) 422-3537 and asking for tech support, this is a somewhat weird one.

 

[adickerson]

Thanks for the advice. I just spoke with Leprecon and they were very helpful. I tried a couple things, but to no avail...

But the plot thickens. I realized that the problem is between only specific dimmer packs, and not other DMX stuff. Here's my setup, in the order that they are daisy chained:

Leprecon LM-850 console ->
Matrix Dimmer Pack (fixtures DO NOT flicker) ->
DP-415 Dimmer Pack (fixtures Flicker) ->
DP-415 Dimmer Pack (fixtures flicker) ->
colorkey RGB LED (does NOT flicker) ->
colorkey RGB LED (does NOT flicker) ->
DP-415 Dimmer Pack (fixtures flicker) ->
colorkey RGB LED (does NOT flicker) ->
colorkey RGB LED (does NOT flicker) ->
Matrix Dimmer Pack (fixtures DO NOT flicker) ->
DMX Terminator

Anyone have any thoughts on why only these specific dimmer packs are giving me problems with this console? None of the dimmer packs have any problems when used with a Microvision.

 

[xander]

Is it possible it has to do with the frequency or baud rate? Maybe the receiver chips in that particular model dimmer don't mesh with what that board is outputting? I don't know anything about lm-850, but if you can adjust those in the settings like you can on other boards, I would try it out. It's not going to hurt anything to try.

-Tim

 

[adickerson]

That's a good thought. I went to look for a setting like that, and didn't find anything. But I did try turning on the dimmer preheat, and that completely got rid of the flashing problem (yay!). Now with the preheat on, I have a ghosting problem (boo). The ghosting actually seems to effect the LED's as well as the DP-415's, but not the matrix dimmers. Hmmm...

I'm better off with ghosting than with flickering, so I'll stick with it for now. I'll try seeing if Leprecon has any advice for me again tomorrow with this new info, and if I learn anything good, I'll let you know! (or if anyone else has any thoughts, I'd love to hear them)

Thanks again for your help!

 

[Amishplumber]

I've run into similar flickering problems before when I've mixed mid range dmx gear of different brands. In my case its usually an older ETC board (think Microvision or expression) with NSI dimmers and ADJ LEDs. Flickering wasn't on cues, it was just a constant single flicker about ever 20 seconds. We have similar setups though.

Solution I've found is to run the DMX through some sort of converter box that has its own DMX chip. I've used both a Pathway DMX converter and an NSI microplex to dmx converter to fix it. Both were set to passthrough DMX mode.

Basically, all the different brands of DMX chips didn't like talking to each other, for some reason that no one's tech support could figure out. Solved it by running the DMX through any device that reads the DMX and encodes it anew.

Thats what I would try anyway. Good luck!

 

[DuckJordan]

thats just changing the outgoing rate of the DMX, certain fixtures don't like certain speeds of DMX transmission. You could eliminate the converter (if thats all your using it for) by going into the consoles menu and changing the rate at which it outputs DMX.

 

[adickerson]

thats just changing the outgoing rate of the DMX, certain fixtures don't like certain speeds of DMX transmission. You could eliminate the converter (if thats all your using it for) by going into the consoles menu and changing the rate at which it outputs DMX.

I've heard this mentioned before when I've had other issues with communication between dimmers and consoles. The only problem is I've never seen any setting for this on any of the boards I've used - we've got an ETC Microvision, an ETC Idea 48 and this Leprecon LM 850.

The way people seem to mention it, it sounds like its a standard thing, but I have yet to be able to figure it out on any of these. Any advice on that front?

FatherMurphy - I'd be willing to bet that your solution would solve this problem. If I can't figure out the DMX rate-changing thing in the board itself, I'll see if I can borrow something similar to what you're talking about to see if it will actually do the trick before I go out and buy one...

Thanks again for your help!

 

[xander]

...we've got an ETC Microvision, an ETC Idea 48 and this Leprecon LM 850.

Wow. You've got a pretty legacy collection of boards there. I don't believe any of those consoles have the ability to change their DMX rates. It is pretty standard nowadays, but not when those were made. So, yes, I would try to find someone with a "converter" to borrow. Or maybe a signal booster would do it? Not sure about that.

Where in Brooklyn are you?

-Tim

 

[FatherMurphy]

I don't think the LM-850 is capable of adjusting the frame rate of the DMX, it's too old a design. Older consoles tended to send the entire 1-512 stream each frame, newer ones often only send updates, thus a faster frame rate and (hopefully) smoother and more responsive results at the dimmer/fixture. Usually, though, if there's a frame rate problem, it's an older device that hates a newer console.

There's also a potential conflict in the end frames - iirc, there is supposed to be a brief pause between frames, or a start/stop code in the first/last frame, that some manufacturers omitted, and others relied on, and this can cause compatibility problems (others more versed in DMX than I can fill in the details).

This is reminding me of a customer who has a collection of old MPX shoebox dimmers, and due to variations in the MPX protocols between manufacturers, some of the packs have to be addressed at 16 or above to work correctly - they ghost and flicker if addressed 1-15, but are rock solid 16 and up.

Amishplumber's suggestion to re-encode the DMX might help, otherwise, try Leprecon again with the new information that the problem is device-specific.

The preheat function is a holdover from analog/incandescent days, when some designers liked to maintain a low voltage to all dimmers so that the filaments would come up faster and experience less thermal shock, or 0-10 volt consoles needed to work with 2-8 volt dimmers. The preheat keeps all channels at 20% or so even when the fader is at 0, and this would be sent as a non-zero DMX intensity, explaining why modern devices react oddly.

 

[Amishplumber]

Just affirming the whole old consoles lacking dmx speed settings things. I often use both Microvision FX's and Expressions and neither has a DMX speed setting. Oldest board I've seen with that setting is an Express.

Also, I've had the same flickering problems mentioned before with an express as well. The DMX speed setting changed nothing. Needed to run it through a converter.

 

[FMEng]

Instead of focussing on the console as the fault, I'd be talking to Elation about why the DP-415 doesn't play nicely with others. That dimmer pack might have a design flaw.