Koch Lab:Protocols/Changing the Hg bulb

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The below steps outline how to remove and properly replace a 100W Hg bulb in an Olympus Hg bulb housing. Make sure to wear gloves as any oils on the bulb can cause it to explode. Also, make sure not to touch the bulb as anything that can burn on it will burn and can cause it to explode.

Once the bulb has been replaced, make sure to run it for at least an hour in order to make sure that the plasma burns in a preferential spot in the electrodes.

Step 1

Remove the Hg lamp from the microscope. First, take out the iris lever.

Next, loosen the set screws holding the lamp in place.

Remove the lamp carefully making sure to include the ND filter sets with removal.

Set the lamp on the table and point it to the wall.

Step 2

Next, unscrew the top of the housing.

Carefully remove the top and set it down next to the housing.

Step 3

Remove the old bulb. Do this by loosening both set screws and pushing down on the bottom holder such that the top of the bulb can be removed from the top housing.

Step 4

Replace the bulb and make sure that you put it in the correct orientation. If not, then the bulb is liable to explode. Just put the bulb in such without tightening it into place.

Step 5

This step is very important. The first thing you do is hold the bottom housing up such that the bulb is flush with the top housing. Once you feel that the bulb is flush, tighten the top screw.

Once the top screw is tightened, tighten the bottom screw. You don't have to do anything fancy with this screw, just tighten it.

Step 6

Replace the top part of the housing and screw it down.

Step 7

Reset the number of hours on the lamp, plug it back in, and turn it on. Make sure the lamp is pointed to the wall and use the focus adjust to focus on the plasma. Adjust the ND filters such that you don't burn out your eyes when observing the plasma. It will look something like the below picture.

This may look correct but it isn't. There is a mirror behind the bulb that reflects the rear of the bulb forward. Adjust the mirror such that you can see both the plasma and the reflected plasma.

Now adjust the mirror such that the two plasmas line up next to each other.

Keep adjusting the two plasmas till they are completely lined up on top of each other. Once they are on top of each other, adjust the lens such that the plasma is uniformly illuminating the wall.

Step 8

Stop the light coming out of the lamp and replace it on the microscope. Make sure to leave it on for at least one hour.


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