Outdoor low voltage lighting problem

[billlite]

I have a two zone outdoor low voltage system with a 600 watt transformer. One zone works OK. One zone went out. I am experienced, so I went to the first light and cut the line and checked the voltage with a voltmeter. It showed the correct 11 volts. I hooked up a known good light fixture and checked the voltage at the light socket (the two holes)--It showed 11 volts.

But, when I put in a working 20 watt bulb, it does not light and it shows no voltage at the line connection. The wires are clean. I even touched the light bulb prongs to the incoming line that showed 11 volts but get no light. The load seems to cause a short circuit or ???
I am mystified.
Thanks for any help.

[HayZee518]

what's the voltage of the bulb?

[billlite]

It was a 12-volt standard Malibu outdoor bulb. Wiring is #14 outdoor low voltage wiring.
Thanks for reply.

[HayZee518]

use the continuity function of your meter and check the light bulb. a filament might look good but electrically it doesn't conduct. all the bulbs should be connected parallel to the line. if they're connected in series, they'll act just like series connected xmas tree bulbs.

[billlite]

use the continuity function of your meter and check the light bulb. a filament might look good but electrically it doesn't conduct. all the bulbs should be connected parallel to the line. if they're connected in series, they'll act just like series connected xmas tree bulbs.

Thanks. It is a good bulb. I checked it on another good line in a new fixture and in it's original fixture. I have also disconnected the remaining lights on the line...I am testing at the first light, about 30-feet from the transformer.

[HayZee518]

then the only thing I can come up with is a break in your line or poor contact where the socket stabs into the line wire.

[billlite]

Thanks again. But one final thing...What I don't understand is that when I test the two-line cable, I get the right reading between the wires at an open connection. (12 volts.) When I attach the known good fixture to that connection, I get the same reading at the connection and in the socket. But when I put in a known good bulb, I not only get no light, I get no reading at the connection. That is the mystery.

[HayZee518]

outdoor lights

600 watts divided by 120 volts equals 5 amps
input-output ratio is 1:10
10 volts on primary equals 1 volt on secondary
60 volts on primary equals 6 volts on secondary
120 volts on primary equals 12 volts on secondary

[billlite]

Thanks for input. It has been awhile, but the problem still is there. I know about electricity and this is a mystery. The setup is a normal outdoor lighting system. It is a parallel line. With the voltmeter I get a reading across the two lnes, but when a load is put on (the light) there is no light and no reading on the voltmeter.

I tried a known good light, same result. It is like the line shorts out when a load is applied.

More ???

[HayZee518]

Try a known good fixture from your first line on the second line. The guts of the fixture may be shorted out.

[HayZee518]

the MALIBU site says to install the first fixture no greater than 10 feet from the transformer. you said yours is 30 feet from the transformer. another thing that came to mind is the LED bulbs they are selling. LEDs only work on DC not AC. LEDs have no filament like a conventional bulb but something called a P-N junction. One pole or element has an affinity of electrons the other pole or element has "holes" which accept electrons. When the LED conducts across its junction it emits photons, visible light. It can also be called a photo-diode.

[billlite]

Thanks for the latest input. This is a professional system that has been in use for nine years or more and worked fine until this problem. There is another line from the transformer and it works OK. I use conventional light bulbs, not LED.

One more thing. When I test the line with the voltmeter I get 11 volts across the lines. When I test the light fixture with the voltmeter in the light socket holes, I get 11 volts. Only when I insert the known good bulb do I get no light and no voitage across the wires. Inserting the bulb causes the problem--like a short.

I will try it with another known good light fixture to see if the fixture is problem.

[HayZee518]

just for reasons of testing - take a fixture base and some scrap wire, install the fixture onto the scrap wire and put its wires across a car battery. if the lamp is good it will light. take the wires off the transformer and splice some test jumpers on it and place these across the car battery.

[HayZee518]

I'm not going to argue about what the vendor has stated.
If there are four terminals on the transformer, try swapping the lines and see if the problem replicates itself.

[billlite]

Another try

I tried one more thing. I took a good known light fixture that works on another circuit both with a working lightbulb. I attached it about 20-feet from the transformer. The line tested 11 volts. The light fixture at the socket tested 11-volts. When the 20-watt pin bulb was installed, the light would not work and the line tested no voltage. I then repeated this wiuth a second known good fixture and bulb. Same result.

By the way, it iks not a Malibu system, but a custom system that has worked for years and works on another circuit from the same 600 watt transformer.

Is there another electrtical test I can try to isolate the problem? I have a standard volt-amp-ohm testing meter.
Thanks.