Power cubes failing at an increasing rate

We have two Sensor systems in our venues. One is almost 20 years old the other about 12 years old. We are experiencing power cube failures at in increasing rate. I've replaced 4 cubes (out of 136 dimmers) in the younger system and 10 to 12 cubes (out of 192 dimmers) in the older system. The symptom is typically a failed on condition. All of these failures are within the last three years, no problems of this sort before that. 

If it were just the older dimmers I would suspect it is just end of life of that component, though at $100 plus per cube it isn't "just." However the fact that the younger cubes are failing also confuses me.

Does anyone recognize this pattern? Could we be using the dimmers in a way that causes this failure? We do use a lot of dimmer doubling. 



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  • ...I am surprised that you haven't seen a response to this from ETC yet... There are two major reasons for failures of "power components", whether they be discrete SCRs or power modules: Heat or electrical surges. Heat can be due to loose line or load wire terminations on the module... make sure the connections are tight. Heat issues are also caused if the module is not bolted down tight or has a poor "thermal" connection to the heat sink. It could also be a localized air flow problem. Although Sensor racks have fans and temperature sensing, a rack running with less than a full load could have several isolated "hot" (=too warm) dimmer modules that would not set off the thermal sensors. As for electrical surges, voltage surges can be caused by (d'oh...) lightning or heavy machinery (think large A/C compressors) starting on the the same utility transformer. Current surges can be caused especially when high-wattage lamps fail. The dimmer choke tends to minimize this, but...

    My suspicion is heat. I know of 30+ year old systems with the SCRs bolted to huge heat sinks that have the original components. I also have some experience with an older system that had the power modules bolted to the rear panel, which had heat sink-like "fins" on the exterior. It depended on "convection" to cool the rear panel. On that system, the modules in the "middle" of the panel tended to fail more frequently; which I felt was because of greater heat build up in the "middle" of the panel. On the Sensor racks, check the "inlet" fins on the modules. Do you have access to a thermal imaging camera?...
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