Solid Fuses: Visible Indicator If Blown?

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Did you ever try the light bulb instead of a fuse ?
Depending on the normal load, you can use a 100 watt light bulb (wattage to vary depending on normal current usage) in place of the fuse. When the light bulb glows much dimmer or not at all then you have found the problem that usually blows the fuse.
Putting the amp meter across the fuse will not depend on the load, but the actual ammount of current that can be sourced. Say the normal load is only 10 amps, your meter is good for 20 amps, but the source is good for 100 amps. If you have an almost short at the load, close to 100 amps is going to try and pass through your 20 amp meter which is now toast , or hopefully the internal meter fuse blows.
You should only put the amp meter in line when you get the fuse to stop blowing. Then it should be safe to see how much current is actually being used.
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On 9/25/2013 9:09 AM, Ralph Mowery wrote:

I had a 100w, 150w and 200w bulbs that I soldered test leads with alligator clips to when I was working as a bench tech back when appliances and TV sets used a lot more power. In the past 20 years, most of the service work I've done has been mobile and not a good place to have glass bulbs bouncing around in a vehicle. I'm sorry but I keep assuming others would do what I do without thinking. The light bulb in series with a Simpson 260 was SOP when working on two way radios to check the DC current draw. A shunt was needed for AC current tests since those meters would only test up to 10 amps DC. A separate AC ammeter worked for bench testing. I had variable power supplies that indicated voltage and current being drawn by equipment when bench testing plus those power supplies had adjustable current limits that would drop voltage to zero when the limit was reached. The small resettable circuit breakers I used were put in series with the DMM when testing current draw. I repeat, never use a DMM to check current in line if you know it will exceed the safety limits of the meter. Test leads can melt or have the tips burned off. It's not a problem to put a DMM across a fuse when testing a radio being powered by a 12vdc power supply which is rated at 3 amps and has a built in circuit breaker like the small power supplies sold by Radio Shack for many years. It's been a while since I've been in a Radio Shack store to buy discrete components or batteries. If I'm working on a small AC appliance that would draw 5 amps/600 watts,(look at the label). The small circuit breaker in series with with a DMM having a 10 amp range is completely safe unless you are dumb enough (like me) to touch the exposed test clips and get a shock. Even if the small circuit breaker is not used and the appliance has a dead short, the 20 amp breaker supplying power to the outlet you are plugged into will trip. The small circuit breakers I once put together on my own are now sold at supply houses with the pigtails and test clip already on them. When repairing electrical or electronic gear, the best test equipment are your eyes, ears and nose. ^_^
TDD
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re: "...unless you are dumb enough (like me) to touch the exposed test clips and get a shock."
...or the banana plug on the end of a jumper cable.
In my case it was the second week of USCG Electronics School training. On the worktable in front of us, we each had a 400 VDC power supply training device which was plugged into a power strip.
There was a ~4" jumper cable, with a banana plug on each end, that connected two sections of the power supply. The jumper could be pulled out to break the device down into smaller sections for troubleshooting training. Basically you were removing the load. The normal procedure was to shut the power supply down, pull the jumper and then power it back on.
Heck, I don't need to go through all that. I'll just hooked my finger into the loop and pull the cable out. So, with my forearm resting on the chassis, I hooked my finger into the jumper and pulled. Too bad one banana plug (on the output side) was a lot looser then the other one. With input side still plugged in, the loose end flipped up and laid against my thumb. With my arm laying on the chassis (read: ground) I became the new load for the 400 VDC.
My arm spasmed and I couldn't pull it away from the chassis. Instinctively, I reached out my other hand to pushed the chassis away. All that accomplished was to cause the current to flow from one hand to the other through my upper body. I was holding a 30 lb power supply up off the table as if it was weightless, yelling "Turn if off! Turn it off!" as my whole upper body spasmed.
The guy at the table in front of me turned around and grabbed the power cord in an attempt to unplug the device. Unfortunately, the power strip was not secured to the table so it just came up with the cord. The guy next to me reached over and slapped the power strip back onto the table which unplugged the device.
I dropped (actually, threw) the power supply onto the floor and they drove me over to the infirmary for an EKG. Other than the burns on my hand, I was apparently OK.
When I came back to class the next day all of the power strips had been screwed down to the work surfaces and 2 other guys had quit electronics school after witnessing my near demise. They quit ET school and I went on to work on devices that had power supplies in the range of 25KVDC.
Luckily (?) I still have the scars on my hand to remind me of how stupid I was. I've been a lot more careful since then.
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On 9/25/2013 3:25 PM, DerbyDad03 wrote:

work on the set in front of the customer who had an odd yet concerned look on her face. I've been shocked, zapped and burned more times than I can count but I never, ever let my guard down around high voltage high current power coming into a building. When I worked as an electrician, my superintendent got a tingle when using an old wooden hot stick while we were connecting some 4,160 volt pad mounted transformers for the underground electrical system we were building. If it had been 13.8kv I doubt he would have gotten just a tingle. All my ladders and push poles are fiberglass because one never knows what you can run into around power systems. I learned long ago to work on everything as though it was energized because it a good habit to get into. One thing I really hate is when I've been working in hot weather and because I sweat like a thunderstorm, I wind up soaking wet with all my clothing soaked and the sweat dripping on the floor. You can tell where I've been by the wet areas on the floor. In this condition, I've had my sweat soaked shirt tail touch a ground while I was working on a panel. Salt water and sweat conduct electricity very, very well. o_O
TDD
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On Wed, 25 Sep 2013 16:19:51 -0500, The Daring Dufas

As a kid I had salvaged a power supply out of an ancient TV that didn't use a flyback system - the main power transformer had taps from, IIRC, 3.5 volts to 25000 volts. The high voltage was at the opposite end from the low voltage. I needed the low voltage to test a small motor I was working on, but I grabbed the wires on the wrong end. I must mention the basement ceiling was something like 5 1/2 ft to the floor decking, about 42 inches to the bottom of the joists. I was just under six feet tall at the time. I straightened up fery quickly and my rock-hard skull caught the end of a nail that held the 1/4" unserlay to the sub-floor, and I popped the head of that nail through the linoleum flooring in the living room above.
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On 9/25/2013 6:58 PM, snipped-for-privacy@snyder.on.ca wrote:

OUCH!! How deep was the hole in your skull or have you always had a hard head? ^_^
TDD
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On Wed, 25 Sep 2013 20:31:11 -0500, The Daring Dufas

It bled a bit, but I guess I've always been a bit hard headed. If anyone told be I had rocks in my head, I'd just take it for granite.
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Sounds miserable. I'd not want to hit a nail with my head, in any situation.
. Christopher A. Young Learn about Jesus www.lds.org .
On 9/25/2013 11:42 PM, snipped-for-privacy@snyder.on.ca wrote:

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On 9/24/2013 5:03 PM, Ralph Mowery wrote:

I agree with the rest, but this in particular. Might be safe across the fuse in something like an amplifier. Power fuses you had better have a CAT rated meter, as in another post. A meter would seldom have a high enough amp scale anyway.

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On Sat, 21 Sep 2013 20:34:59 -0500, The Daring Dufas

The VD is Voltage Drop. You check across a fuse in energized circuit on the volt scale to see how many volts are dropped across it. If it is close to zero, the fuse is probably good (or the circuit is not closed). If you see full circuit voltage, the fuse is bad.
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This is not an answer to your quiz, but we used to test BFR (Big Fracking Resistors) by banging them on the edge of the workbench.
These were foot long, 1" diameter ceramic resistors used in LORAN-C transmitters. Before we'd meter them, we'd bang them on the edge of the workbench. These resistors had a habit of getting brittle before they failed. We preferred that they cracked while out of the transmitter rather than when they were in a 15K VDC circuit.
The arc across a cracked resistor makes a lot of noise.
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The best fuse tester I have used is a Fluke T3. You can go across a fuse in a circuit and it will automatically show if the fuse is ok by showing continuity or if it blown it will show voltage if there is any voltage above 24 volts. Meters are nice in some cases, but this little tester is almost impossiable to blow as long as the voltage is under 600 volts. Nothing to turn on, turn off , or adjust. http://www.transcat.com/PDF/T3TESTER.pdf
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On 9/21/2013 10:22 PM, Ralph Mowery wrote:

I used a good old Wiggy for years when doing a lot of electrical work and I'm sure I could find it in my stuff if I haven't lost it. The Fluke T3 is a modern variation which looks like the old Wiggy.
http://www.drillspot.com/products/73461/Wiggy_6610VT1_Voltage_Tester
http://tinyurl.com/k67f6ke
TDD
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On 9/21/2013 9:22 PM, Ralph Mowery wrote:

The tester also has a CAT3/CAT4 rating - a real good idea if you are testing a BFF. That means the meter won't blow up, which some non-CAT rated meters might when used on high capacity circuits.
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Anything I use will have a CAT rating when working on any voltage above about 50 volts.
Fluke put out a film that shows what can hapen with the less expensive meters when used on equipment that can have a very high current capacity. Even putting the wrong fuse in a meter rated cat3 or more can get you in trouble. The beter meters will have a fuse in the ohm meter section. If you hapen to put the meter in the ohm or amp setting and get across a voltage source and the fuse blows, but the not rated fuses can arc over and have the effect of not blowing. In almost no time the leads insulation melts and you are across the voltage source. Or the leads explode from the excessive current.
That little Fluke T3 tester is very handy. Small enough to slip in the back pocket. They also make a T100 multimeter about the same size that works very well . It will do voltage and up to around 1000 ohms and has a provision to act like a clamp on ampmeter. It is also almost impossiable to blow up. We used them at work and would often go across fuses on 480 volt 3 phase circuits. Most often just using the ohms setting and going across fuses. Never did see one go bad even when the fuse was blown. I probably checked thousands of fuses this way on running equipment.
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That's going to keep me awake, wondering. I hope you give the answer, eventually. After the suitable amount of begging, of course.
. Christopher A. Young Learn about Jesus www.lds.org .
On 9/21/2013 9:34 PM, The Daring Dufas wrote:

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(PeteCresswell) wrote:

Hi, With or without fuse in circuit? You are measuring between fuse terminals? If you don't read anything(no voltage read) fuse is OK. If you read voltage fuse is blown.
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It's possible to read zero volts across a in-circuit fuse that is not blown.
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DerbyDad03 wrote:

Hi, Of course if the circuit is alive.
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On 9/21/13 7:22 PM, (PeteCresswell) wrote:

The indicator fuses I've seen have little windows on them. Example here: http://tinyurl.com/q3q65g6
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