What the heck???

demogo

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OK, I guarantee this is a first for this site.

I'm debugging -- of all things -- my landscape lighting. Here's what's going on:

1) The bulb stopped lighting in the socket one day
2) I measured the output at the transformer (ac 12v) -- right at 12v measured with DMM going into the wires feeding the light
3) I measured the output at the socket -- right around 11.1v
4) I measured continuity on the bulb -- it has continuity so it isn't blown
5) I took a few scraps of wire and hooked it up directly at the transformer and ran it to the bulb and it lit
6) I can stick these scraps of wire into the sockets of the fixture and get 11.1v and touch them to the bulb and it will NOT light

What the heck is going on? Is 11.1v not enough to light a 12v bulb? Surely it should light but be dim? Or is there something else going on?

It looks like I'm losing a bit of current as I've dropped from 12 at the transformer to 11 at the light fixture...

Thoughts?
 
It's not a fluorescent light, it's a halogen bulb so there shouldn't be a starter or anything else.
 
Halogen lamps are manufactured with enough halogen to match the rate of tungsten evaporation at their design voltage. Increasing the applied voltage increases the rate of evaporation, so at some point there may be insufficient halogen and the lamp goes black. Over-voltage operation is not generally recommended. With a reduced voltage the evaporation is lower and there may be too much halogen, which can lead to abnormal failure. At much lower voltages, the bulb temperature may be too low to support the halogen cycle, but by this time the evaporation rate is too low for the bulb to blacken significantly. There are many situations where halogen lamps are dimmed successfully. However, lamp life may not be extended as much as predicted. The life span on dimming depends on lamp construction, the halogen additive used and whether dimming is normally expected for this type.

Could this combination of a slightly lower voltage and the cooler weather we've been having cause your problem? I wonder if you take the bulb in the house for a while and let it warm up, if you could take it back out and get it to light in the socket?
 
Could this combination of a slightly lower voltage and the cooler weather we've been having cause your problem? I wonder if you take the bulb in the house for a while and let it warm up, if you could take it back out and get it to light in the socket?

Nope. Bought a new bulb and direct from the store it does the same thing.

I also sprayed some compressed air into the holes of the socket (it's an mr16 socket) to make sure there was nothing in there and it didn't help.

But the fact that I can stick wires into the socket holes and measure the voltage on the end of them and touch them to the bulb and it doesn't light suggests that it's not a physical connection issue.

Other than the drop-off of the voltage I don't know what else could be going on. But a 12v bulb should light at 11.1v I'd think, even if it were slightly dimmer.
 
Should I be able to measure the amperage on the wires?
 
KLOV's best and brightest have been defeated by landscape lighting? :(
 
It is possible that the bulb has a Zener in it preventing it from running at too low of power.

Check continuity across the bulb from both directions. If you are open one direction and shorted the other then a Zener is the most likely cause based off of your other observations.
 
Good idea but I just checked and I have continuity no matter which way I put my leads on the light.
 
Are your other bulbs lighting? Does this bulb work in the other spots? Other bulbs don't work here? Other working sockets measure the same?
 
Are your other bulbs lighting? Does this bulb work in the other spots? Other bulbs don't work here? Other working sockets measure the same?

Just 1 lamp so I don't have others to test with.

This bulb worked when I directly tied into the wires coming off the transformer so it's not the transformer and not the bulb.
 
If this has direct burial wiring, you probably have corroded/damaged/mole eaten/mouse eaten wires.

Yeah, it's buried. I suspect you're right -- it's not the transformer and not the bulb, so it's either something in the socket or in the wiring because that's all that's left.

There's one spot where the wires from the socket splice into the landscaping wire that was acting up right after I first installed this thing and that's probably where I'll go first tomorrow.

If I cut the wires there to take a measurement and I need them joined again I can always crimp them together and seal them with hot glue or twist them together and then use some heat shrink tubing to seal them.

I'll probably go buy another run of 25' of landscape wiring tomorrow depending on whether the wire or the socket seem to be culprit.

The thing I can't explain is why I'm getting 11 something volts out of the wire and the bulb's not lighting...
 
OK, I guarantee this is a first for this site.

I'm debugging -- of all things -- my landscape lighting. Here's what's going on:

1) The bulb stopped lighting in the socket one day
2) I measured the output at the transformer (ac 12v) -- right at 12v measured with DMM going into the wires feeding the light
3) I measured the output at the socket -- right around 11.1v
4) I measured continuity on the bulb -- it has continuity so it isn't blown
5) I took a few scraps of wire and hooked it up directly at the transformer and ran it to the bulb and it lit
6) I can stick these scraps of wire into the sockets of the fixture and get 11.1v and touch them to the bulb and it will NOT light

What the heck is going on? Is 11.1v not enough to light a 12v bulb? Surely it should light but be dim? Or is there something else going on?

It looks like I'm losing a bit of current as I've dropped from 12 at the transformer to 11 at the light fixture...

Thoughts?

recheck the voltage UNDER LOAD with the bulb hooked up. Im willing to bet its down to nearly nothing under load. aka corroded wire somewhere underground.

VOltage does not equal current. You can have 12 volts unloaded, but if the wire is messed up it wont condict much current, and a retest of voltage under load will confrrm that. ou are correct- its either the wiring or socket.
 
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recheck the voltage UNDER LOAD with the bulb hooked up. Im willing to bet its down to nearly nothing under load. aka corroded wire somewhere underground.

VOltage does not equal current. You can have 12 volts unloaded, but if the wire is messed up it wont condict much current, and a retest of voltage under load will confrrm that. ou are correct- its either the wiring or socket.

You know, I think you're right.

I did actually try to check the voltage under load once or twice and the numbers went down to near zero and I thought I just wasn't getting a good connection with my testing. But I bet I was.

What you're saying here makes a lot of sense -- it's almost got to be the wiring. I'll start with the splices that I mentioned earlier and test from there. I bet that light's working tomorrow night! :)
 
Fixed.

It was the splice connectors that I was suspicious of; the ones that had acted up last year.

They were used to splice the wires from the landscape light wiring to the wires coming from the light itself. Very poor design on their part so I had to engineer my own solution.

I cut off the splice connectors, stripped the wires, twisted them together, crimped them together with a Bob Roberts crimp nut:

http://www.therealbobroberts.net/crimpnut.gif

Then I took a hot glue gun and filled up the space in the nut with hot glue until it was sealed, did the same on the outside of the nut until it was sealed, used some cable ties for strain relief, cable tied the wires together, put them into a very small plastic bag, and used more cable ties running down the length of the plastic bag to try to make it water tight. Then I buried it under mulch.

The wire nuts themselves should be water tight I hope after the hot glue treatment; the bag is just for extra insurance.

The light looks nice shining up in my tree.

Thanks for the tips guys!
 
I'm debugging -- of all things -- my landscape lighting.
Thoughts?

Thoughts? aaaaaa .... this entire thread should be in the OT section? (I realize it won't get the exposure it would here, but them's the rules).
 
Thoughts? aaaaaa .... this entire thread should be in the OT section? (I realize it won't get the exposure it would here, but them's the rules).


Wrong section, huh? Well, the landscape lighting contraption can certainly be called a machine and he is getting some form of amusement out of repairing it. So, I would certainly call this an 'Amusement Machine' in this instance...
 
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