12k Sparks! Oh My!

[tommygdawg]

Hey all

I've had my HMI cherry popped! I waited 15-20 minutes before flicking on the mag ballast to my 12k, it was on for a couple minutes, and then I got a couple sparks out the side! Egads! Then I looked inside and this is what happened to one of the leads...

hmiburn.jpg

Any thoughts on what I should do about this? Can I just re-wrap it, or does the entire lead need to be replaced?

[tommygdawg]

And, it wasn't my fault! I didn't think a close-to-20 minute wait would be an issue. That's a lot of downtime, especially since it wasn't on long in the first place. The left lead is cracked in half, and the insulation is broke further down. The lead itself is brittle. I've attached photos. Thoughts on how to replace this? By the way, you can also see the nice melt/scorch on the inside where the sparks dropped.

20160916_213347.jpg20160916_213842.jpg20160916_213954.jpg
20160916_213857.jpg

[dwiener]

No amount of cool down time could have prevented that. There's a lot of heat in a 12k. With age insulation dries out and rots. If there was a loose connection the copper itself corrodes and the resistance increases causing the lead to heat up even more. I'd bet if you checked the other lead it's probably brittle as well. I'd rewire the head. Make sure you use properly rated and insulated cable, and leave enough slack for the lamp to travel back and forth on the focusing track. If you don't feel comfortable doing it yourself send it to a qualified technician.

[tommygdawg]

No amount of cool down time could have prevented that. There's a lot of heat in a 12k. With age insulation dries out and rots. If there was a loose connection the copper itself corrodes and the resistance increases causing the lead to heat up even more. I'd bet if you checked the other lead it's probably brittle as well. I'd rewire the head. Make sure you use properly rated and insulated cable, and leave enough slack for the lamp to travel back and forth on the focusing track. If you don't feel comfortable doing it yourself send it to a qualified technician.

Thanks for the thoughts! Any idea where I can source the wires? I'd normally just buy cable and wire it in, but these particular leads end in metal blocks that screw into the lamp assembly, which makes them a bit more of a specialty item. I've emailed and called Cinemills but have heard nothing back from them. Any thoughts on this?

Thank you!

[dwiener]

Hard to tell from the connector but could the wire have had a crimp on sleeve that is now welded into that terminal block? Besides the normal operating voltage and current there is also a momentary high voltage from the igniter to get the arc to strike. No visible markings on the existing wires? My guess would be 6 awg for a 12k but don't hold me to it.