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In Reply to: RE: Electronic SAFETY when Building, any GUIDE ARTICLES ? posted by drlowmu on August 18, 2014 at 12:20:34
The tubelab piece is good, but pretty wordy. Here are some short rules I follow:
FOR UNPLUGGED TUBE GEAR:
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Discharge the power supply caps. I use a 100Ω resistor hardwired to high-voltage leads with alligators at one end and a probe at the other. Clip the alligator to the chassis, and touch the probe to each power supply capacitor terminal for a few seconds. It's less dramatic than shorting the p/s caps with a screwdriver. (The screwdriver method works, but will give a big audible pop and spark, and can result in your screwdriver being welded to the capacitor terminal.) Use your multimeter to confirm that the caps are drained.
If you don't do this and get zapped, it is unlikely to injure you, but it does hurt.
FOR ANY GEAR PLUGGED IN, TUBE OR SOLID-STATE:
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1. Rubber-soled shoes. No exceptions ever.
2. One hand in your pants pocket. No exceptions ever.
3. Plan what you are going to do before you do it. Don't just start poking about with probes and screwdrivers. If you have to get a probe or screwdriver into a tight spot on a live circuit, rehearse it first with the gear unplugged, one hand in your pocket, and caps discharged so you know you can accomplish what you need to do without shorting out anything (including you.)
4. If in doubt, stop. Put it aside, walk away, clear your head. Come back tomorrow.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
Follow Ups:
Good rules! Here are a few more:
I'd suggest using a variac to bring up new projects. You can get them on ebay for a reasonable amount and they can sure help. In the last 20 years I've only made one significant boo-boo and that was somehow connecting the output of a choke directly to ground instead of a cap, as was intended. The variac saved it.
As much as possible I connect meter leads before power up so I can watch what's happening, and that way I'm not poking around a live circuit with a probe that might slip.
I also like to use an analog meter on B+ (a used Simpson 260 is inexpensive and an excellent meter). Watching the needle swing on an analog meter can be very informative and help you spot trouble quicker. Aligator clip leads are handy but be careful if you link them together that you don't then brush against a hot connection.
Variacs are invaluable, cheap, and look cool sitting on the shelf when you're not using them. I always use one to bring up old gear, but admit that when I put a kit together or mod a circuit I generally take a "damn the torpedoes" approach, plug it in and watch for smoke. Haven't had any in the first forty-five years. When I do get some I'll probably just hang up the soldering iron.
I used to use the Heathkit IM-18 VTVM, as it was easy to keep accurately calibrated. It was a good meter, but you have to remember to change the C-cell battery every year or so to prevent having a leaker. These days I use a Fluke 110 rms multimeter, which gives pretty much the same information on its display, including a good LCD approximation of an analog meter movement. It's more expensive, but it includes ac voltage and frequency, dc voltage, audible continuity/diode check, resistance, and capacitance. It's a good tool, and good tools make me happy.
WW
"A man need merely light the filaments of his receiving set and the world's greatest artists will perform for him." Alfred N. Goldsmith, RCA, 1922
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