Glass fuse with pigtails?

LOTs of them at Digikey for 35 cents-ish (more for slow-blo). Try searching for through-hole and glass or cartridge. Both 5x20mm and

Yes, I've soldered wires to regular fuses and it worked for me (the fuse still conducted afterward). There is soft solder of some type on the ends.

Best regards, Spehro Pefhany

I'll assume 3AG size fuses. Regular fast blow fuses solder easily. However, soldering usually doesn't work with slo-blow fuses, where the internal spring and series resistor tend to fall apart. I've had better luck when I immerse the fuse in water, with only one end cap out of the water, and using low temp (eutectic) solder. I've also tried wrapping the glass and opposite end cap in aluminum foil to act as a heat sink, with good success. Fortunately, I don't have to do this every day.

I've also seen fuses with some manner of metal or plating on the ends that are impossible to solder. They might be stainless or galvanized. For those, you can use fuse clips (as John Fields suggested):

Instead of clips, I sometimes see end contacts made from a wound spring with a pigtail for soldering into the PCB. Of course, I can't find any examples online. I've made a substitute from a heavy paper clip wrapped around a slightly smaller mandrel but usually prefer to replace the springs with a real PCB fuse holder.

You best bet is to solder wires to a fuseholder, then install that on the PCB, then you can plug standard fuses into the clips.

Jon

If you're blowing soldered-in fuses that often, something else is wrong.

Usually if the pigtail fuse goes on a switching supply it's one of two things.. the fuse element was fatigued by years of turn-on surges, or one of the main switching transistors has gone short, and probably taken a diode or two out of the bridge with it.

Plus it's sort of stupid to monkey with a safety device to save 35 cents. Replace once, then if it blows again, troubleshoot further.

Cheers

Phil Hobbs

The repair FAQ says: Supply dead, fuse blown - shorted switchmode power transistor and other semiconductors, open fusable resistors, other bad parts. Note: actual cause of failure may be power surge/brownout/lightning strikes, random failure, or primary side electrolytic capacitor(s) with greatly reduced capacity or entirely open - test them before powering up the repaired unit.

I see a few blown fuses in PC supplies. It's most often the result of a bulging low voltage capacitor finally deciding to short. The switcher should not oscillate with a shorted output, but with a lesser load, odd things happen. Usually the switcher starts for about a second, blows the fuse, and then quits. If I replace the fuse with a much larger value, it follows the same pattern, but without blowing the fuse. I guess operating with bulging and leaking capacitors isn't defined in the specs.

Another common blown fuse problem is on overclocked and heavily modified machines. The owner has the audacity to actually run the power supply at it's rated power output. For example, a 450 watt power supply actually running at around 450 watts. 200 watt video cards are common so this is not science fiction. Most such supplies will barely produce the rated power for very long and protect themselves by either a thermal shutdown, or that's lacking, blowing the fuse.

I'm also seeing blown fuses caused by a mismatch between the inrush current limiter, and the two big electrolytics in the switchers input voltage doubler section. Normally, these electrolytics hold their charger for a long time (as I've demonstrated by zapping myself). If the power supply is turned on and off suddenly, the caps remain mostly charged and there's no inrush current. Nearby is the inrush surge current limiter (PTC thermistor) the is high resistance when cold, low resistance when hot, and is suppose to cool down very quickly. That usually works as expected until some moron glues the thermistor to the side of the ATX case, or adds a bleeder to the to big electrolytics. That causes the capacitors to discharge BEFORE the thermistor cools down. When the next power glitch appears, the thermistor is still hot and low resistance, while the caps are discharged. The inrush current then blows the fuse. Breaking the RTV glue between the thermistor and the ATX case is usually sufficient to prevent further blown fuses.

Grumble... First day of my vacation and I have to drag myself to the office to deal with customer emergency. I should have left town.

If they are 0.25 x 1.25" fuses, and if you have enough room above the fuse, you can get a holder that clips on top of the blown pigtail fuse and allows you to install a non-pigtail fuse. TV service shops used to use them a lot.

Cooper Bussmann part number 3434, or Mouser part number 504-3434. The $8 Mouser wants is a dumb price; for that much money I'd just install a regular fuseholder. Maybe you can find them cheaper somewhere.

Matt Roberds

Exactly. You should only have to replace a fuse *twice* -- the first time when you realize you OVERLOOKED something; the second time being the charmer! (while ONCE is prefered, I don't always expect to catch every problem initially -- especially if there was "collateral damage")

Exactly. Fuse blown? Look at load. Try *powering* load (from a lab supply) once you are reasonably sure it "should be OK" -- to verify this (CL power supply so you can see what the load is *really* doing).

Once you're sure the load had nothing to do with the failure, move backwards looking for obvious faults. Then, *think* about why they may have happened -- instead of just blindly repairing them!

I've got to place a Digikey order anyway, so I'll just tack them onto the order and save myself the hassle/uncertainty.

Thx!

Clever! I'm not sure it would fit in the space provided -- but, it would be a nice thing to have in my bag-of-tricks!

Thanks!

GC electronics used to sell adapters to convert standard AGC/3AG style fuses into pigtail. They were would of copper plated steel. You pushed them onto the ends, and soldered the pair of wires into the circuit. I can't access their website right now. My anti virus says there is a trojan on the main page and blocks access.

That's what these LOOK to be. But, my attempts at trying to pry them off the ends of the fuse have been ineffective -- leading me to suspect they may be more than just a "friction fit".

I will trust your AV! ;-)

You have to twist the old fuse to loosen the grip. Or GENTLY twist the spring with small pliers from the end of the winding. Otherwise, they could vibrate loose.

That is a package of 10 for $7.95.

No, that's an "each" price. Look at the PDF catalog page:

That 10 on the original link is the "factory pack quantity". Mouser says...

Ah, makes sense. I will try that at my next opportunity! Always a bit nervous with a bit of glass in my hands...

Thanks!

--don

You can often remove the metal cap by heating it until the glue melts, and slip it off the glass.

I've had reasonable luck using a CD battery tab welder to weld tabs onto fuses. Don't think I'd risk selling anything I fixed that way. ;-)