Replacing ETC L86 dimmers

TWhite

Member
I want to check in with electricians or TD's who work in venues equipped with ETC L86 dimmers, or have replaced them in the last 5 years.

The question is, are they still working well, does your venue have plans or is it budgeted yet? Also, if you've already changed out to dimmers from this century, were your L86's failing or was it just time to align with current technology?

Thanks all,
Tom White
San Francisco
 
LIke many dimmer racks, the dimmer modules themselves are basically circuit breakers, chokes, and SSR's. All easily diagnosed and replaceable. It's the control modules that can become problematic and can defy component-level diagnosis. My advice would be to invest in some spare control modules and even a few dimmer modules (for spare parts). Both available on Ebay or from service providers like Lite-trol who may have spare modules or key parts available for sale. I'm fairly certain ETC still supports the L86 line, although they probably don't have an endless supply of any discontinued or custom parts. It is not unusual for racks to have a working life of 30-40 years.
 
I agree with microstar but in addition, incandescent dimmers and fixtures won't be around and in regular use for ever. I'd guess that new dimmers today will not be in use for their expected life time. The money you can save by just updating electronics and not replacing dimmers would be much better spent moving towards LED or saved for LED or other solid state sources.
 
LIke many dimmer racks, the dimmer modules themselves are basically circuit breakers, chokes, and SSR's. All easily diagnosed and replaceable.

We just renovated our theater to fully utilize our 96 channels of LM86-2400 dimmers (circa 1980's I think). Each electric now has dimmer circuits for tungsten and fixed power for intelligent lighting. In shaking out all the new dimmer circuits, I've eaten through my surplus trays and now I have a collection of trays where only one channel doesn't work. One or two are stuck ON but mostly, the bad channels just don't work. I suppose thats simply the opposite of being stuck ON (being stuck OFF). And a couple more randomly go off and then return.

I see no physical burn marks or leaking modules. I suppose I could send them to Lite-trol or contact ETC but is there a technical manual or website on how to diagnose the failing component? It would be a nice summer project to refurbish them. TIA
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The SSR could of gone bad after so long. Like mentioned above only a few components in these things.
 
As noted, one is one channel, the other is two. The terminals are different. Outside of that, SSR's pretty much operate the same; control voltage in gates the back-to-back SCRs inside. About the only real wild card (outside of voltage/current) is the ZVC feature. Some SSRs are designed to only switch on near the Zero Voltage Cross. Good for motors and other things. Cannot be used for dimmers. SSRs for dimmers must be able to turn on at any point in the AC waveform. Well, just about anywhere.. There has to be some voltage across them for the firing circuit to switch them on.
 
We just renovated our theater to fully utilize our 96 channels of LM86-2400 dimmers (circa 1980's I think). Each electric now has dimmer circuits for tungsten and fixed power for intelligent lighting. In shaking out all the new dimmer circuits, I've eaten through my surplus trays and now I have a collection of trays where only one channel doesn't work. One or two are stuck ON but mostly, the bad channels just don't work. I suppose thats simply the opposite of being stuck ON (being stuck OFF). And a couple more randomly go off and then return.

I see no physical burn marks or leaking modules. I suppose I could send them to Lite-trol or contact ETC but is there a technical manual or website on how to diagnose the failing component? It would be a nice summer project to refurbish them. TIA
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@LesWilson One (two) point(s) I haven't noticed anyone blatantly outright telling you is the breakers and chokes almost never fail leaving only the SSR / Solid State Relay / Back to back SCR's / TRIAC's / IGBT's (Which ever type of solid state device) as virtually the only component to fail; they can fail open circuit (off) or they can fail shorted (on). Sometimes when they fail shorted they can fail spectacularly so with smoke, stench and obvious evidence of burning. Other times, not so much.
When replacing, be certain to replace with exactly the correct type and model, although conceivably from another manufacturer and be certain to clean the heat sink's mating surface and apply a thin fresh coating of silicone heat transfer grease to ensure good thermal dissipation from the solid state device to its heat sink. Occasionally solid state devices are electrically insulated from their heat sinks. Carefully check the old unit upon removing and replace the insulator if one was fitted by the manufacturer.
Toodleoo!
Ron Hebbard
 
I have seen breakers go bad in the dual LMI modules. It is my understanding that these breakers are no longer being manufactured and ETC will replace them if the module is sent back for repair.
 
Have you called ETC support? They very likely have several people with lots of experience with these. Also, since you have some modules with one circuit good and one circuit bad, you should be able to cannibalize the good parts to get more units working. Oh and the couple that go off then come back on, sure sounds like a thermal issue. Do you regularly clean the racks?
 
Thanks everyone. I clean the filters twice a year. Some trays, which I am ignoring as far as re-furbishing goes, were failures from visible breaker damage. I realize I could cannibalize breakers from SSR failed units and assume the SSRs in the breaker failed units are OK but there's the risk that the SSR is also bad so it's a waste of time ... maybe the SSR is the reason the breaker failed...

Also, the breakers and SSRs are for two circuits so no cannibalizing two trays to get one good one without major re-engineering of the tray to use two SSRs each half working... not ready to go that far. I'm wealthy in spare trays as the original installation in early 1990's was for over 96 circuits. In 2003, it was handed down to my venue and deployed as a 96 circuit unit. More than enough. My focus is therefore on the easy SSR fix to keep what we use for our long throw fixtures going while we convert the short throw stuff to intelligent fixtures.

I found the 2-pole SSRs for sale online for around $95 a piece.

@JohnD - is there a different fix for the thermal issue like reseating the SSR with new thermal cement or is it a goner already?

According to my research, ETC re-engineered the tray from the dual breaker to two single breakers. Not ready for that expense.
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The dirty little secret is that inside that SSR potting are about a dozen components such as SCRs, photo-triacs, diodes, resistors, capacitors, and other goodies that make up the firing circuit. Even if the SCRs themselves are good, any failure inside the potting renders the assembly bad. On the bright side, service is easy! Yes, a breaker can go bad, but far less likely. If both channels are out, you may also want to meter that little thermal cutout located next to the SSR. It should meter a dead short and only opens if things get too hot. In 40 years and a thousand repairs I have only ever seen one bad choke. Short of snapping a wire off of it, or bypassing the breaker and cooking it, they just don't fail. The one that I did see simply had the input lead wrapped so tight it cut into the output lead, and only took a small piece of fiberglass sleaving to fix.
 

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