Hi, I'm trying to fix a center light dmx CTL-6 of 250w by ACME. The problem was that the light didn't turn on. I opened it and found that the bulb had white spots so I thought it didn´t work. But before buying another bulb I checked the supply voltage noticing that it had 220v. I looked for the supply voltage required for that bulb and found that it needs 94 volts. Then I believed that maybe it burn out because of the voltage it received, but watching the supply circuit looks as if 220v were the expected supply voltage for the bulb. Now I don't understand how this circuit works, like if it reduces the voltage to 94 after the filaments get hot, or the bulb works with 220v and the information I found could be wrong. So, does anybody knows what could I do to find the problem by not wasting on a bulb and probably burning it?
Thanks in advance.
I attached some photos of the circuit and the bulb.

 

If you notice the large white object (ballast) on the upper right, it is labeled 220/240 VAC input and 94 V output.

 

Yes, thanks. I noticed that but also I got confused about from wich terminal is it supposed to get the 94v, because it has the "L"(which I guess is Line) that is connected to the transformer, and the other output says 230V 60Hz, that is connected to the ignitor.

 

Yes, thanks. I noticed that but also I got confused about from wich terminal is it supposed to get the 94v, because it has the "L"(which I guess is Line) that is connected to the transformer, and the other output says 230V 60Hz, that is connected to the ignitor.

And also none of the outputs deliver the 94v.

 

And also none of the outputs deliver the 94v.

Did you consider that the ballast is bad, not the bulb?

 

Did you consider that the ballast is bad, not the bulb?

Yes, and none of the outputs of the ballast is labeled with 94v, it is just marked inside the rectangle. Every output match with the voltage marked, that is why I don't get where the 94v is supposed to come from.

 

You have to understand how gas discharge lamps work.
Before the lamp is struck, meaning the gas is not yet ionized, the lamp is essentially an open circuit. The voltage at its terminals is therefore identical or almost identical to the AC mains.

When the igniter strikes or ionizes the lamp, the gas inside will go into a very conductive state, and would draw humongous large quantities of current from the mains. That is where the ballast comes in....it limits the ionized lamp to a safe current level. The lamp will develop a certain voltage at that current, which in your particular lamp is 90 volts.

The igniter may be faulty and not striking the lamp. WARNING: igniters produce about 2.5 kV to ionize the gas. It can severely shock you and/or destroy a DMM if you attempt to measure it.

One question for you: what is the circuitboard on the left side of the picture?

 

You have to understand how gas discharge lamps work.
Before the lamp is struck, meaning the gas is not yet ionized, the lamp is essentially an open circuit. The voltage at its terminals is therefore identical or almost identical to the AC mains.

When the igniter strikes or ionizes the lamp, the gas inside will go into a very conductive state, and would draw humongous large quantities of current from the mains. That is where the ballast comes in....it limits the ionized lamp to a safe current level. The lamp will develop a certain voltage at that current, which in your particular lamp is 90 volts.

The igniter may be faulty and not striking the lamp. WARNING: igniters produce about 2.5 kV to ionize the gas. It can severely shock you and/or destroy a DMM if you attempt to measure it.

One question for you: what is the circuitboard on the left side of the picture?

Hi!, that PCB is used to control some servomotors that rotate little mirrors used to reflect the light, it has another one used to rotate an item which is around the bulb that changes the color of the light, and also it feeds the fan. And of course, is connected to the mandatory lighting controls.
Thanks for your answer!!!
Then I guess I will have to get the bulb and test it to figure out the issue.

 

And also none of the outputs deliver the 94v.

You will only measure 94V when the lamp is running. It's a series inductive ballast. With no load the output voltage will be the same as the input voltage. And, as it is just a series inductor, it has no specific input and output.
A metal halide lamp has no filaments. It is ignited by a 2.5kV pulse between the electrodes provided by the ignitor

 

Big Clive on YouTube released a video today explaining how metal halide bulbs work. Definitely worth a watch as Clive explains things very clearly.