I am planning on building a vintage tube radio from schematics. Part of the radio will include its (multi-voltage output) power supply, with an AC power cord, AC switch, and transformers.

Are they any (U.S. legal, regulatory, or commonly accepted good engineering practice) standards that I should follow in sourcing the components (transformer specs, type of cord, fuses, etc.), and performing the wiring and assembly? (soldering, connectors, insulators, shielding, etc.)

The goal would be to end up with a radio that is safe for myself, a family member, or a guest to operate.

  • \$\begingroup\$ Experience level: Many decades ago, as a teenager, I assembled several radio kits, one "hot chassis". There seem to have been less safety rules back then (e.g. commonly available chemistry sets that could make things go "boom", etc.) \$\endgroup\$
    – hotpaw2
    Aug 7, 2019 at 16:52
  • \$\begingroup\$ Are you intending to sell this item? There really isn't any "rules" for personal use home-made electronics... \$\endgroup\$
    – Ron Beyer
    Aug 7, 2019 at 16:54
  • 1
    \$\begingroup\$ @RonBeyer you might still be accountable for damages you cause that you could've avoided with reasonable effort. \$\endgroup\$ Aug 7, 2019 at 17:12
  • \$\begingroup\$ @MarcusMüller Yes, of course there is the "common sense" thing to apply. If you tried making yourself a "waterproof toaster" and didn't follow any safety guidelines, that would be gross negligence. If you use a 30AWG wire for a 30 amp load in a Christmas Tree ornament, again, negligence. If you get your connector 1mm too close and it doesn't do anything, nobody is going to burst through your house and arrest you. This would be different if you are selling it to the public... \$\endgroup\$
    – Ron Beyer
    Aug 7, 2019 at 17:32
  • \$\begingroup\$ @RonBeyer absolutely on point! \$\endgroup\$ Aug 7, 2019 at 17:34

1 Answer 1


Anything touching the power transformer primary side (line cord, connectors, switches, fuses, etc.; and of course the transformer itself) should be UL listed. Any conductive surface that might come in contact with the user must be double-insulated. There are spacing rules regarding how close together conductors can be, and there are similar rules for the high voltage secondary circuits. If the final assembly is in an insulated box, that is the majority of the protection for the user.

UL1950 / 60950 / EN60950 is the standard covering personal computers, and is a good standard for general use. Medical devices have a more restrictive standard.

Shielding is a different matter, and gets into FCC part 15 rules. But for a linear amplifier with a linear power supply, the major shielding issue concerns keeping noise out of the circuits, not preventing the circuits from interfering with other devices.


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