electrical question

[Cody Jacobs]

I was working on a student production a few days ago that used solely daylight heads. We were running off house power with your typical blend of 15 and 20 amp circuits connected to about 7 smaller HMI heads, a package which consisted of 4 1.2k's and 3 575's. As this was equipment from our school it was an amalgam of new and old fresnel and PAR fixtures mostly from Arri, though two of the 1200's were old Sunrays. Each of the 1.2k's had their own dedicated 20amp circuit just to play it safe while the 575's were connected in-line with a few kino's and a dedo spread out on three 15amp circuits.

 

We didn't have any issues with popping breakers or anything of that nature, but a peculiar situation arose with the newest of our Arri 1.2k Pars. For some reason the connection between the male Edison of the ballast power cable and the female Edison of the line providing house power kept heating up to the point of nearly melting. At first I thought this might be caused by the fact that we had a rather long cable run to get to the light which was placed outside even though the stinger was beyond the proper rating for such a situation. So I switched the head to a line that ran a much much shorter distance yet the problem still persisted. To double check I made sure that each of the lines I had tested the head on were indeed 20 amp circuits and that nothing else was running off of these. As we had insured before this was still the case. So this was apparently not the issue. To further test what could be happening we checked to make sure that the lines were secure and free from anything that might be cause excessive impedence and sure enough they were fine. I then tried running the ballast off of flicker free mode at regular 60Hz output just to see if for some reason that might have been doing anything. Of course the troubled continued.

 

Unfortunately we wrapped for the day before we could test any further, and like most student shoots the schedule was too hectic and time consuming to get the head out again and try a few other options. Now I established that it wasn't a faulty stinger because I tried different ones. So as far as I could tell it was either a bad ballast or an issue with the head itself. We couldn't afford to spare a ballast from another light because they all had to contine working so that variable was not tested. I'm just wondering if anyone had any technical guesses at what might have been going on just for my own curiosity sake. Thanks.

[Jeff Tanner]

It's pretty simple in this case...

 

Resistance = Heat

 

Either in the stinger or the ballast power cable there is a bad/old/corroded connection. Snip off the burnt ends and replace the connector with a new one. It will be as good as new.

 

Respectfully,

 

Jeff Tanner

[EricUlbrich]

probibally a bad ballast, it sounds like the ground/neutral part of the edison isnt really doing its job to balance the load on the wire. I would send it back to the rental house and get a new ballast.

[Howard Newstate]

Yeah, I would check the edisons on the stinger and ballast first. Replace as needed, if that doesn't work then have a tech check out the ballast. Most likely its one of the edisons gone bad.