The story:
please note this second hand. During a Recent focus at one of the older buildings, a light froze in the on position. This particular circuit had been functioning well, up to this point, and even tested out normal three weeks prior. The head electrician eliminated all variables in the board, and after a time between 15 minuets less than half an hour decided to check the dimmer racks. He came in and found that the circuit in question was producing an incredible amount of heat. he flipped the breaker off and contacted the House T.D. who pulled the card. The TD found that the SSR was cooked. The center of the SSR was burnt out, while there was no scorching anywhere else on the SSR. The TD then replaced the dimmer unit with another one from our "good" pile of units. When he flipped the breaker back on the new unit started to heat up in the same way as the old one. The Dimmer unit was pulled and the light was re-circuited. That's the story.
the investigation:
I came in the next day, and immediately looked at the rack. Nothing was obviously loose or shorted where the unit tied in. I looked back to the raceway, The circuit had been replaced recently but it tested out fine. I put in a new unit and tested the circuit. It was not functional. The cable had disappeared, but the instrument was working well with no shorts. I performed a quick autopsy on the "cooked" card and found that The trigger on the circuit in question had indeed blown open since I could get continuity between points A1 and A2 which I should not have been able to get without trigger voltage. I then tested the breakers and found that they were in working order. I removed the SSR and found that the heat sink was very weak, but present. I replaced the old SSR. We found a spare DMX card from downstairs and replaced it and found that while the circuit in question was working other ones were not, so we put back the original DMX card. I marked the spare as bad. When I replaced the original DMX card, suddenly the circuit was functional again. The Circuit is now off, and I Have never seen it produce any heat.
Conclusions or Questions?
So, this is my first month in this space and I'm still working out a lot of the Bugs. I know for a that the SCR was blown open and most likely cooked while the PE hunted through the board. I'm willing to believe that a short in the cable caused the SSR to blow open in the first place even though I can't prove it. I have not eliminated The failure of the Choke even though I have no good way to test it. I'm also willing to believe that we have more bad cards than I thought we did. The two things that I'm the most concerned about 1. The heat from the second unit that the TD reported, and 2. That I might be missing something else I haven't thought of. Any thoughts Ideas or suggestions? Is there a more sinister culprit possibly lurking in the wings, or is this just an Isolated incident caused by old dimmers?
please note this second hand. During a Recent focus at one of the older buildings, a light froze in the on position. This particular circuit had been functioning well, up to this point, and even tested out normal three weeks prior. The head electrician eliminated all variables in the board, and after a time between 15 minuets less than half an hour decided to check the dimmer racks. He came in and found that the circuit in question was producing an incredible amount of heat. he flipped the breaker off and contacted the House T.D. who pulled the card. The TD found that the SSR was cooked. The center of the SSR was burnt out, while there was no scorching anywhere else on the SSR. The TD then replaced the dimmer unit with another one from our "good" pile of units. When he flipped the breaker back on the new unit started to heat up in the same way as the old one. The Dimmer unit was pulled and the light was re-circuited. That's the story.
the investigation:
I came in the next day, and immediately looked at the rack. Nothing was obviously loose or shorted where the unit tied in. I looked back to the raceway, The circuit had been replaced recently but it tested out fine. I put in a new unit and tested the circuit. It was not functional. The cable had disappeared, but the instrument was working well with no shorts. I performed a quick autopsy on the "cooked" card and found that The trigger on the circuit in question had indeed blown open since I could get continuity between points A1 and A2 which I should not have been able to get without trigger voltage. I then tested the breakers and found that they were in working order. I removed the SSR and found that the heat sink was very weak, but present. I replaced the old SSR. We found a spare DMX card from downstairs and replaced it and found that while the circuit in question was working other ones were not, so we put back the original DMX card. I marked the spare as bad. When I replaced the original DMX card, suddenly the circuit was functional again. The Circuit is now off, and I Have never seen it produce any heat.
Conclusions or Questions?
So, this is my first month in this space and I'm still working out a lot of the Bugs. I know for a that the SCR was blown open and most likely cooked while the PE hunted through the board. I'm willing to believe that a short in the cable caused the SSR to blow open in the first place even though I can't prove it. I have not eliminated The failure of the Choke even though I have no good way to test it. I'm also willing to believe that we have more bad cards than I thought we did. The two things that I'm the most concerned about 1. The heat from the second unit that the TD reported, and 2. That I might be missing something else I haven't thought of. Any thoughts Ideas or suggestions? Is there a more sinister culprit possibly lurking in the wings, or is this just an Isolated incident caused by old dimmers?