Mac 2K lamp blowing fuse

hobbsies

Active Member
I'm having an issue with a Mac 2k (I know, shitty, throw them away, etc etc, can't though, have to use these things :( ), where when we strike the lamp it either trips the circuit breaker the lights plugged into or blows a fuse right away. We are running them at 120V on separate dedicated 120V 20A circuits. They have been switched to run at 120 according to the shop that repairs them. I'm wondering what are the possible causes for this? Is the lamp dying? Is the ballast going bad? We've replaced the fuses in this fixture several times to no avail.

thanks in advance

ipad typing is hard
 
When they were switched to 120V were the fuses replaced with the correct amperage for that voltage. According to the manual:

20 AT (time delay) main fuses for use with AC supplies of 100 - 120 volts.
15 A main fuses for use with AC supplies of 200 - 250 volts.
 
It could be the lamp, is it over on hours? The longer the lamp is in service the longer the gap the arc has to jump. And with the larger gap is has to pull more and more power to be able to bridge that gap.
 
It could be the lamp, is it over on hours? The longer the lamp is in service the longer the gap the arc has to jump. And with the larger gap is has to pull more and more power to be able to bridge that gap.

This is what I was thinking.

Fuses we are using 20A time delay fuses, though they say 250V
 
might be the lampbase, after a long use the wires underneath gets exposed and blows the fuse. so if they're old and been through alot have a little peak at it.
 
Blows them right away?
Short of the lamp forming a conductive stripe, it sounds more like a ballast or wiring problem. Excessive lamp draw may pop the protection, but not right away. Swap the lamp first for test, but my hunch is "no."
 
I agree with JD. If the fixture will works fine until you try and strike it you're probably dealing with a ballast/wiring issue. The first thing I would look for is some black scarring from where wiring might be shorting out to metal. After that I'd probably swap out the ballast and see if that changes anything.
 
I agree with JD. If the fixture will works fine until you try and strike it you're probably dealing with a ballast/wiring issue. The first thing I would look for is some black scarring from where wiring might be shorting out to metal. After that I'd probably swap out the ballast and see if that changes anything.

I think we're cutting this unit. We can't even find a lamp in the city.
 
I think we're cutting this unit. We can't even find a lamp in the city.

?? It's one of the most common lamps on the market: Part # 54268 SharXS HTI 1200/D7/60. But, definitely sounds like more of a ballast issue than a lamp issue. (phew).
 
Based on personal past stupidity, I know putting a Mac2k Wash set for 208V on a 110V line, it will operate normally (pan tilt etc) until you strike the lamp, then you will blow fuses, scratch your head, and eventually figure it out. If your unit runs correctly until you strike the lamp, then I'd put my money on what kind of voltage it is looking for. Check the manual. It's a bummer to not know but trust a repair shop, and please just make sure your fuses follow the manual specs. And yes, the lamp should be easy to get ahold of, especially in Chicago.
 
Yeah that makes no sense to me either, there are plenty of shops in Chicago that should have that lamp on hand.

I don't really understand what the issue was with finding a lamp, I wasn't in charge of it, but I found one hiding in a closet, finally. New lamp seems to have fixed things with tripping the breaker, but it blew the fuses a day later. Several other of the movers have been going through fuses at least once a week. We're using what's recommended in the manual (20A 250V slow blow ceramic fuses). But I don't fully understand what's going on with them. The show is 1 day from opening. All the movers have been to a shop for repair recently (in the past 6 months), they're running on seperate 20A 120V breakers via 12 AWG SOOW edison cable. We've measured the voltage and got between 119 and 121 at all of the outlets including across the cable.

I'm out of ideas, and I can't tell them to not use them. I wish I had a better understanding of what is happening.
 
Install a twofer at the end of the run and meter the voltage and see if it drops. Also if you have an Edison breakout meter the amperage the unit is pulling.

Your answer may be in the numbers regarding the breakers tripping. First of all, lets look at what a 20 amp breaker can hold for a long period of time:

20A X 80% = 16 amps

Now, how much does the fixture draw? Well, 1500 watts for the lamp, maybe another 100 watts for the ballast, and another 250 watts for all the electronics and motors. That's a total of 1850 watts.
( http://www.martin.com/product/product.asp?product=mac2000washxb )

1850 / 125 volts = 14.8 amps, so the breaker holds.

Now, what happens as the voltage drops and the electronics compensate:

120 = 15.41
115 = 16.08
110 = 16.81
100 = 18.50

So, you want to get a voltage reading at the fixture while the rest of the show is running. As you can see, everything can be working fine and the breaker could still trip if the voltage dips enough.

I can't say I ever measured one in normal operation, nor do I have the plate handy to see what its listed draw at a given voltage is, but the problem may be a simple matter of voltage drop in cabling or line voltage changes.

If the nameplate rating is higher than 1850, then matters become even more critical. Also, electronic ballast alignment can produce some big changes in draw. The lamp may be working fine, but the ballast is out of alignment and running the lamp at 1800 watts (for example) and the fixture be drawing 2100 watts.

Remember, even a properly running ballast is +/- 10% and that's once the lamp is up to temperature. The "strike/warm-up" time runs higher yet.

I think this is why the stock Mac 2k is set up for 208-240 volts. It's just too close for 120, although I am sure in most cases they will work on a 20.

EDIT: The above info was based on the above link. Most of the other links for Mac 2k link to the older 1200 watt unit. Although my first thought would be they draw less, I am seeing their draw listed as 18 amps at 120, 20.9 amps at 100 volts. (Electronic ballast) Darn close for something with a 20 amp fuse and a 20 amp breaker. Even their fuse rating for 240 volts is 15 amps. 20 may be the limit for the fuse holder!
 
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Install a twofer at the end of the run and meter the voltage and see if it drops. Also if you have an Edison breakout meter the amperage the unit is pulling.

Is this so I can meter the voltage with the mover on and plugged in? Don't think I have a meter capable of metering the amperage they're pulling unfortunately.

In response to JD's post, I'll have to try measuring voltage with all the stage fixtures on. The breaker panel is pulling from the same feed as the dimmers, I believe. Thanks
 
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Yes the twofer is so you can meter the voltage while the mover is on. Also turn on your stage lights if it from the same feed (transformer or switch gear). Also if the power factor cap or electronics that control it are starting to go out the fixture will begin to draw more amperage. My personal rule of thumb is if it is over 1000 watts run it off of 240. Movers like 240 much more than 120 (less current draw on all of the electronics) traces on circuit boards have never liked high amperage loads. I have some with holes blown through them from the trace breaking down to failing. It typically happens right where a component is soldered such as an SCR. Also if the fixture has a multi voltage tap and frequency tap make sure they are set correctly. I have had a round of Martin fixtures blowing fuses and after tearing them down and metering everything I noticed they were set for 50hz rather than 60. After setting the tap to 60hz the problem went away.
 
Yes the twofer is so you can meter the voltage while the mover is on. Also turn on your stage lights if it from the same feed (transformer or switch gear). Also if the power factor cap or electronics that control it are starting to go out the fixture will begin to draw more amperage. My personal rule of thumb is if it is over 1000 watts run it off of 240. Movers like 240 much more than 120 (less current draw on all of the electronics) traces on circuit boards have never liked high amperage loads. I have some with holes blown through them from the trace breaking down to failing. It typically happens right where a component is soldered such as an SCR. Also if the fixture has a multi voltage tap and frequency tap make sure they are set correctly. I have had a round of Martin fixtures blowing fuses and after tearing them down and metering everything I noticed they were set for 50hz rather than 60. After setting the tap to 60hz the problem went away.

This is very good information. Thank you
 

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