How can I mitigate risk of electric shock?

Question

I want to start a new project and build a PC in an antique style radio. The back of it says "CAUTION RISK OF ELECTRIC SHOCK. DO NOT OPEN"

It's just a 120V 60Hz 8 watt radio, but this warning has me wondering how to discharge the thing safely. What part of the board does this warning pertain to? The transformer?

As long as it's disconnected (it is, right?) you shouldn't worry about that. Nice idea anyway! — clabacchio, Feb 25 '12 at 20:35
@clabacchio Well, there could still be charged capacitors in it, so I wouldn't say it's 100% safe. — exscape, Feb 25 '12 at 20:49
If it's been unplugged for at least a minute, it should be fine. — Olin Lathrop, Feb 25 '12 at 21:03
Try turning it on while it's not plugged in. That should discharge all the caps — samoz, Feb 25 '12 at 22:38
@samoz: That doesn't necessarily work with old tube circuits. Without the cathodes getting hot there could be nothing draining the high voltage cap. — Olin Lathrop, Feb 25 '12 at 23:22

JustJeff · Accepted Answer · 2012-02-26T00:36:12.777

5

First, never, ever ever work on a tube radio while it's plugged in!

Assuming you just want to gut out the radio circuits and keep the case, if it has been unplugged for a year, it's probably safe.

There were two common reasons for such labels. First being, capacitors can hold lethal charges for hours to days after the circuit is powered off. The other is an abominable practice from the early 20th century of bonding the neutral wire of the power cord to the radio chassis, and counting on (1) a polarized plug, (2) correct domestic wiring, and (3) the insulating value of the case to protect the user.

If this radio is truly an antique, and you know no one has tried plugging it in recently, it should be safe enough.

edited Feb 26 '12 at 00:36

answered Feb 26 '12 at 00:30

JustJeff

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"First, never, ever ever work on a tube radio while it's plugged in!" Surely (with adequate training, experience and safeguards) someone's got to work on live equipment to debug and repair? – Transistor May 25 '16 at 23:11
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Engineers working on old live chassis sets normally do so with it connected to the mains via an isolating transformer. – Ian Bland May 25 '16 at 23:48

How can I mitigate risk of electric shock?

1 Answers1