This is something that if often overlooked and taken for granted. Tube amplifier circuits contain high voltage, many time of what you household voltage may be. It is important to follow a few safety rules when building and testing tube electronics.

  • Always make sure your work area is free of clutter and possible short circuits such as loose solder, bare wires and tools.
  • Make sure that you are not distracted when equipment is powered up, i.e., don’t be talking on the phone or watching a youTube video about cute kittens, a simple distraction can cause a big problem.
  • Keep kids away while testing. It’s a good idea to teach them of the danger of poking around in daddy’s projects.
  • Make sure things are properly grounded. This can be a problem on some older ‘Hot’ chassis equipment, but when building new projects make sure you have a good chassis ground.
  • Fuse your project, you can fuse both the low and high voltage side of the power supply. This is more of a ‘Keep things from blowing up’ tip, but it has been one that has saved a few parts in the past. This is especially true when first powering up equipment that you built.
  • Try to keep one hand out of the mix when probing or touching things in the equipment.
  • Don’t make the mistake of touching something to see if it is hot. THIS IS A GOOD WAY TO GET BURNT AND SHOCKED. Double whammy.
  • Don’t touch the exposed back side of aluminum electrolytic capacitors, you are likely touching something with voltage potential.
  • Wear goggles when first powering up exposed electronics. I have had a few capacitors blow up and shoot debris like a shot gun
  • Before assuming the equipment is safe to work on, pull the plug and check the high voltage caps for any voltage remaining. You typically should have bleed resistors on them but this is not always the case, so a quick check with the DVM will keep you from getting zapped.
  • If you have a variac (Variable AC supply) it’s a nice thing to slowly power up new projects and wait for the smoke. Many have Watt and Volt meters to show off any pending problems before they get too bad.

Do you have more?  Send them, and I’ll add them to this list. Remember this is just a SHORT list of things to be careful of when working on any high voltage based equipment. I have left out some of the more obvious ones like working barefoot in a puddle of water with wet hands.

Be careful, be safe, be productive!

EZ260 Tube Amplifiers and Tube Projects