- 1). Unplug the electronic equipment from the AC wall outlet. Allow at least 30 minutes to let the high-voltage capacitors discharge before performing any servicing. This will also let hot components cool off.
- 2). Using a screwdriver or nut driver, open the equipment's service panel. The vacuum tubes should be readily visible.
- 3). Using a small cloth to protect your fingers, gently grip the tube by the top and carefully wiggle it slightly side to side to loosen it in the socket. Pull straight up to remove the tube. Some vacuum tubes may be shielded by a cylindrical metal sheath. This can be removed for servicing the tube by a simple push-and-twist or pulling motion. Save the sheath to protect the tube after servicing.
- 4). Examine the tube. You should see the tube number, which may be all numerals or a combination of numbers and letters. Examples: 2AX2, 12AU7, 809. This is the number you'll need to know when purchasing a replacement.
- 5). Test the tube. The tube tester will have a variety of sockets and settings to cover various tube types. If the equipment has several tubes and you don't know which one is faulty, remove, test and reinsert each tube until you find it. When you find the faulty tube, mark it "bad" with a piece of masking tape and marker and set it aside.
- 6). Order a replacement tube from a tube supplier.
- 7). Compare the replacement tube with the old one to verify that it's the correct part. Note the orientation of the pins on its base. Match it up with the orientation of the holes in the tube's socket. Push the new tube down vertically into the socket with moderate force until it's seated firmly.
- 8). Discard the old tube by wrapping it in several layers of newspaper and placing it in the trash. Some tubes contain mercury vapor. If this is the case, dispose at an appropriate hazardous waste center, as you would a fluorescent bulb.
- 9). Replace the equipment's service cover.
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