Forums

Bad fuse holders.

Started by Bitrex January 10, 2012
I was finishing up a project earlier today, and on hitting the power
switch it's completely dead.  It's operated off the line with a
transformer, and after a little debugging I realize something is wrong
with the fuse, or more specifically, the fuse holder.  It's one of the
little cup style deals like the one in the bottom right in this image:
http://www.hiwtc.com/photo/products/8/02/92/29216.jpg

Inside the cup are a spring and a (brass?) terminal clamped around the
wire end.  I find that one half of the holder has continuity, but the
other doesn't. I take that half out of the circuit and measure it with a
multimeter; it reads in the megohms.  At first I thought there might be
some oxidation on the contact that's preventing a good connection, but
nope, there's good continuity between any two points on the contact.

Cut to the chase: the stranded fuse holder wire had vaporized just
inside the wire casing at the contact connection point. Evidently
whatever machine was used to crimp the connectors on the ends pulled the
wire too hard in the process, so at that point the wire was down to just
a couple strands.  Then the inrush current killed it.

I bought the fuse holders from an "overseas" supplier on eBay because I
thought "They're fuse holders, what could go wrong."


Bitrex wrote:
> I was finishing up a project earlier today, and on hitting the power > switch it's completely dead. It's operated off the line with a > transformer, and after a little debugging I realize something is wrong > with the fuse, or more specifically, the fuse holder. It's one of the > little cup style deals like the one in the bottom right in this image: > http://www.hiwtc.com/photo/products/8/02/92/29216.jpg > > Inside the cup are a spring and a (brass?) terminal clamped around the > wire end. I find that one half of the holder has continuity, but the > other doesn't. I take that half out of the circuit and measure it with a > multimeter; it reads in the megohms. At first I thought there might be > some oxidation on the contact that's preventing a good connection, but > nope, there's good continuity between any two points on the contact. > > Cut to the chase: the stranded fuse holder wire had vaporized just > inside the wire casing at the contact connection point. Evidently > whatever machine was used to crimp the connectors on the ends pulled the > wire too hard in the process, so at that point the wire was down to just > a couple strands. Then the inrush current killed it. > > I bought the fuse holders from an "overseas" supplier on eBay because I > thought "They're fuse holders, what could go wrong." > >
And now you know why they were possibly being sold on E-Bay at such a good price. Most likely too many defects in a run and some one that works there, E-bayed them instead of allowing them to hit the land fill. Just a prognosis of mine :) Jamie
On Tue, 10 Jan 2012 13:55:54 -0500, Bitrex
<bitrex@de.lete.earthlink.net> wrote:

> >I bought the fuse holders from an "overseas" supplier on eBay because I >thought "They're fuse holders, what could go wrong." >
Fuse holders are a safety device and you don't care about quality or safety? I remember using a Swiss made finger release fuse holders in the 80s with all the VDE, UL marks. It was ment to be safe to change fuses with power applied. When I got a shock and complained the answer was oh yes the data sheet is wrong! Fuse holders can melt, have inadequate safety clearances, be marked as UL and VDE and never tested.
Raveninghorde brought next idea :
> On Tue, 10 Jan 2012 13:55:54 -0500, Bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> >> I bought the fuse holders from an "overseas" supplier on eBay because I >> thought "They're fuse holders, what could go wrong." >> > Fuse holders are a safety device and you don't care about quality or > safety? > > I remember using a Swiss made finger release fuse holders in the 80s > with all the VDE, UL marks. It was ment to be safe to change fuses > with power applied. When I got a shock and complained the answer was > oh yes the data sheet is wrong! > > Fuse holders can melt, have inadequate safety clearances, be marked as > UL and VDE and never tested.
Likely the wiring was wrong and the fuse holder was OK. Saw many of those over the years. The hot was wired to the outer end and could touched. The were Engineering Changes in the armed forces and in IBM to correct these factory faults that were nothing to do with the holder itself. :-@
On 1/11/2012 4:23 AM, Raveninghorde wrote:
> On Tue, 10 Jan 2012 13:55:54 -0500, Bitrex > <bitrex@de.lete.earthlink.net> wrote: > >> >> I bought the fuse holders from an "overseas" supplier on eBay because I >> thought "They're fuse holders, what could go wrong." >> > Fuse holders are a safety device and you don't care about quality or > safety? > > I remember using a Swiss made finger release fuse holders in the 80s > with all the VDE, UL marks. It was ment to be safe to change fuses > with power applied. When I got a shock and complained the answer was > oh yes the data sheet is wrong! > > Fuse holders can melt, have inadequate safety clearances, be marked as > UL and VDE and never tested.
This type of fuse holder is literally two pieces of wire - I thought that there weren't too many ways to get two pieces of wire wrong! As often the case, reality destroyed my assumptions, and lesson learned. Speaking of safety, apparently some DIYers resort to constructing their own "fuse holders" out of random junk: http://blog.makezine.com/archive/2010/12/heat-shrink-fuse-holder.html
On 1/10/2012 5:57 PM, Jamie wrote:
> Bitrex wrote: >> I was finishing up a project earlier today, and on hitting the power >> switch it's completely dead. It's operated off the line with a >> transformer, and after a little debugging I realize something is wrong >> with the fuse, or more specifically, the fuse holder. It's one of the >> little cup style deals like the one in the bottom right in this image: >> http://www.hiwtc.com/photo/products/8/02/92/29216.jpg >> >> Inside the cup are a spring and a (brass?) terminal clamped around the >> wire end. I find that one half of the holder has continuity, but the >> other doesn't. I take that half out of the circuit and measure it with a >> multimeter; it reads in the megohms. At first I thought there might be >> some oxidation on the contact that's preventing a good connection, but >> nope, there's good continuity between any two points on the contact. >> >> Cut to the chase: the stranded fuse holder wire had vaporized just >> inside the wire casing at the contact connection point. Evidently >> whatever machine was used to crimp the connectors on the ends pulled the >> wire too hard in the process, so at that point the wire was down to just >> a couple strands. Then the inrush current killed it. >> >> I bought the fuse holders from an "overseas" supplier on eBay because I >> thought "They're fuse holders, what could go wrong." >> >> > And now you know why they were possibly being sold on E-Bay at such a > good price. Most likely too many defects in a run and some one that > works there, E-bayed them instead of allowing them to hit the land fill. > > Just a prognosis of mine :) > > Jamie >
It's too bad, all the other items I've bought from this seller (tranistors, ics) to use in hobbyist projects have seemed to be "real deal"; at least they look and function indistinguishably from the real parts. Maybe they're all high quality fakes, I don't know - but for just projects for myself the money I save is worth the risk. I guess their electromechanical selection is not quite up to par, apparently.
On Wed, 11 Jan 2012 06:07:50 -0500, the renowned Bitrex
<bitrex@de.lete.earthlink.net> wrote:

>On 1/10/2012 5:57 PM, Jamie wrote: >> Bitrex wrote: >>> I was finishing up a project earlier today, and on hitting the power >>> switch it's completely dead. It's operated off the line with a >>> transformer, and after a little debugging I realize something is wrong >>> with the fuse, or more specifically, the fuse holder. It's one of the >>> little cup style deals like the one in the bottom right in this image: >>> http://www.hiwtc.com/photo/products/8/02/92/29216.jpg >>> >>> Inside the cup are a spring and a (brass?) terminal clamped around the >>> wire end. I find that one half of the holder has continuity, but the >>> other doesn't. I take that half out of the circuit and measure it with a >>> multimeter; it reads in the megohms. At first I thought there might be >>> some oxidation on the contact that's preventing a good connection, but >>> nope, there's good continuity between any two points on the contact. >>> >>> Cut to the chase: the stranded fuse holder wire had vaporized just >>> inside the wire casing at the contact connection point. Evidently >>> whatever machine was used to crimp the connectors on the ends pulled the >>> wire too hard in the process, so at that point the wire was down to just >>> a couple strands. Then the inrush current killed it. >>> >>> I bought the fuse holders from an "overseas" supplier on eBay because I >>> thought "They're fuse holders, what could go wrong." >>> >>> >> And now you know why they were possibly being sold on E-Bay at such a >> good price. Most likely too many defects in a run and some one that >> works there, E-bayed them instead of allowing them to hit the land fill. >> >> Just a prognosis of mine :) >> >> Jamie >> > >It's too bad, all the other items I've bought from this seller >(tranistors, ics) to use in hobbyist projects have seemed to be "real >deal"; at least they look and function indistinguishably from the real >parts. Maybe they're all high quality fakes, I don't know - but for >just projects for myself the money I save is worth the risk. I guess >their electromechanical selection is not quite up to par, apparently.
They are, no doubt, middlemen, and what you get today is not necessarily what you get tomorrow, even if it has an identical part number and looks very similar. It could come from an entirely different factory, be made with different tooling and materials, and have a different (or no) QC procedure. Caveat emptor. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
On Wed, 11 Jan 2012 05:32:36 -0500, Bitrex
<bitrex@de.lete.earthlink.net> wrote:

> >Speaking of safety, apparently some DIYers resort to constructing their >own "fuse holders" out of random junk: > >http://blog.makezine.com/archive/2010/12/heat-shrink-fuse-holder.html
I can see doing something like this in a pinch and for temporary use. Otherwise whats the point to it. By the time you buy the springs and heat shrink tubing, you could have bought a fuse holder. Plus you cant change the fuse on this thing, you have to redo the whole thing. From experience, I find heat shrink tubing to be some pretty pricy stuff.
On 11 Jan., 20:54, j...@myplace.com wrote:
> On Wed, 11 Jan 2012 05:32:36 -0500, Bitrex > > <bit...@de.lete.earthlink.net> wrote: > > >Speaking of safety, apparently some DIYers resort to constructing their > >own "fuse holders" out of random junk: > > >http://blog.makezine.com/archive/2010/12/heat-shrink-fuse-holder.html > > I can see doing something like this in a pinch and for temporary use. > Otherwise whats the point to it. =A0By the time you buy the springs and > heat shrink tubing, you could have bought a fuse holder. =A0Plus you > cant change the fuse on this thing, you have to redo the whole thing. > From experience, I find heat shrink tubing to be some pretty pricy > stuff.
heats shrink pricy? unless you get something fancy its a 1-2$ for 4 feet at digikey A fuse is mostly there to prevent something from catching fire if something goes horribly wrong, not really something you should need to change -Lasse