Help - Light won't turn on! How to fix/repair?

[Pat Engh]

LTM Pepper - 650 Watt Fresnel Tungsten Light

I was about to shoot green screen and would it not turn on -- had to cancel.

Not the bulb.

Where would I take this to get looked at? Or should I just send it to the LTM company? It's like 7 years old but hasn't had a whole lot of use.

[Nate Haustein]

You know, I'm sure someone will give a good reason not to do this, but why not open it up and see if anything is amiss? Should be a pretty simple dissection...

I had a pair of Lowell Pro-Lights that stopped working, basically a simple sort of fresnel, and it only took me a hour or so to replace the frayed internal connectors. A trip to the hardware store for some pressure fit electrical connectors and a wire stripper seemed to do the trick.

Now, I enjoy taking things apart and figuring out how they tick, so self-repair might not be a solution for everyone, but it's quite possible the fix is simpler than you might think.

[Don Bloom]

not familiar with that particualr light but most lights I've worked with have a switch in the power line. They're usually plastic of some sort and the little brass connctors in side go wonky and BAM! No power, no light or whatever.
Should be pretty simple to fix it. Open up the switch (usually 2 small phillips head screws) by pass the switch and plug it in to see if it works. If it does, then change the switch, if it doesn't put it all back together, open up the light head and look for anything that might be unconnected, burnt or just doesn't look right.
BTW, when mucking around with the switch or in the light head itself, make sure the light is UNPLUGGED! I didn't once (notice I said ONCE) and I got lit up. I was a mess for 2 days. My wife saw some humor in it after she knew I was OK, I saw no humor in it at all. ;-)

[Nate Haustein]

Another option is to bring it to your local lighting/grip rental house. I'm sure they could take a look at it for you.

[Pat Engh]

^ thanks - fast replies. Awesome

[Steven Digges]

+1 on what Don said. But I would add you can trouble shoot many AC issues by testing the flow to see where the stoppage is, without taking things apart first. That works if you have some basic knowledge of using a simple tester. If you don't, don't do it. It requires things to be plugged in when testing.

Now we know why Don used to use hair spray to keep his hair down. He says he doesn't anymore. I'm not sure if that is because he could care less now, or if there is none left. Old guys RULE!

[Don Bloom]

Steven,
It's that I don't care that I hardly have any anymore! ;-)

[Warren Kawamoto]

+1 what Steven said about a tester. I always have one in my gear at all times. A continuity tester (multimeter from Radio Shack) tells you if a connection is good or not. It also has a volt meter, and you can tell exactly where power is not flowing simply by testing the electrical outlet first, then the switch, then the bulb socket in that order. If power is reaching the socket but the bulb is still not lighting, check the continuity of the bulb, pin to pin. If there is continuity, your bulb is good, and the connection between the socket and bulb is bad. A loose connection here will arc and erode the brass inside the ceramic socket. Jiggling the bulb while in the socket sometimes helps. If it still doesn't light, the socket needs to be replaced. As Don said, a bad switch is fairly common, and the next thing to go is the lamp socket. Look carefully at the socket, sometimes you'll see black arc marks from a loose bulb.

[Warren Kawamoto]

[QUOTE=Don Bloom; (notice I said ONCE) and I got lit up. I was a mess for 2 days. My wife saw some humor in it after she knew I was OK, I saw no humor in it at all. ;-)[/QUOTE]

That means you BRIGHTENED her day!

[Tom Morrow]

I just made use of my radio shack voltmeter on set the other day. A practical fixture was failing to light the new bulbs, and we spent quite a bit of troubleshooting before determining that loose connections between the socket tabs and bulb itself were the culprits. Bending them in with a screwdriver solved the problem.

[Tom Guiney]

Light troubleshooting process:

First step is always: Is the power coming to the unit good? plug something else into it, or use your multimeter to check to see if you have somewhere between 100 and 140v (I'm assuming USA standard 120v electrical system and lighting instruments) . Faster is to use a plug-in tester, the little red or yellow thing that looks like a male plug that has some LEDs on the back that light up if it's plugged into good power.

Power is good, but light still doesn't work: Use the continuity feature on your multimeter. Find out where the circuit is being interrupted. Start at the power source and work your way down the line to the bulb.

Logically you must work your way down the line from the source towards the bulb, but practically speaking, the bulb being bad is one of the most likely places to fail. Pull out the bulb (no skin contact to bulbs!) and touch the probes to the two contacts of the bulb. Continuity? Then the bulb is good and the problem is in between the plug and the bulb. No continuity? replace the bulb.

Use your probes to check for voltage between the two contacts of the bulb socket. Voltage is good? Bulb continuity is good? Then maybe the bulb wasn't properly seated in the socket. Make sure it is firmly seated. The bulb contacts in the head are a possible place to interrupt the circuit, if there's a lot of burning or corrosion or foreign matter that could be in the way of the circuit, or the bulb just isn't in right.

Next place to check is the switch. One way is you can open it up and use your multimeter to check that you have proper voltage when you touch your probes to the two wires that come from the line-side. If the electricity is making it to the switch but no farther, the switch is probably bad. You can bypass the switch if you can't replace it. The switch opens and closes a gap in one conductor, so if you connect the two ends of that conductor together on one terminal inside the switch assembly, there should be a continuous circuit and you'll be in business, albeit without a working switch.

If you want to test the switch independently, check for continuity between the line-side and load-side terminals with the light unplugged. when the switch is closed/on, you must have continuity between those two terminals. Even if it looks good and you don't have continuity, the switch is no good. Same goes for checking bulbs. Continuity is the only definitive test.

One way that works to find out where along a line your circuit is interrupted is with a "voltage sniffer". IT's a little wand that lights up in the presence of voltage. They can be a little unreliable, but they are fast and convenient.
https://www.google.com/search?q=volt...hrome&ie=UTF-8

You can plug the light in and run your sniffer along the cable, starting at the power source. The wand should stay lit up all the way along the line up until the point where the the line is broken. This would ferret out a bad switch quickly. The wand is lit up on the line side of the switch, but not on the load side- ok you've got a bad switch.

Another funny thing that could be wrong is if your plug is not making good contact inside the outlet; that you can fix by spreading out the tines of the plug or else replacing the plug. That could be a problem with the outlet as well. Try the lamp in a different outlet that you know is good.

Fixing tungsten lights is really pretty simple- just find out where the circuit is interrupted.

Be methodical. There is either no power coming to your light or the circuit is interrupted somewhere. Find that point and replace it.


Tom Guiney
Dp, Gaffer, inventor
Airboxlights.com
SF Bay Area