QUALITY AND SECURITY OF "LITTELFUSE" PRODUCTS

Geoffkait 4-8-2016 8:11am EDT
If fuses were not directional in AC circuits then we wouldn’t be getting all these reports of directionality. The data sheets provided on the HiFi Tuning web site contain the statement that even for AC - Resistance measurements directionality of fuses was noted. Case closed.

Regarding the measurements described in the HFT paper (which Nonoise was kind enough to link to earlier in this thread) which purport to support the notion of fuse directionality:

1)Resistance measurements related to directionality were provided for 16 different HFT fuses, having current ratings ranging from 1.6 amps to 20 amps, as well as for a few competitive fuses and standard glass and ceramic fuses (the specific make of the "standard" fuses being unspecified). The differences in resistance for the HFT fuses in the two directions ranged from 0.000002 ohms to 0.000120 ohms. The differences in resistance for the competitive fuses were a bit greater in some cases, with the worst cases generally being the standard fuses, for which there was one isolated case having a measured difference of 0.005200 ohms.

IMO those numbers are so miniscule as to be:

(a)Laughable.

(b)Very possibly attributable to changes in the voltage of the battery in the measurement meter, from measurement to measurement (each measurement imposing a slight drain on the battery), and from minute to minute. Or if the meter was AC powered, to the very slight differences in AC line voltage that may occur from minute to minute, as various loads are turned on and off at nearby locations.

(c)Very possibly attributable to differences in contact pressure and contact area between the meter’s probe tips and the contacts on the fuse. The paper presents separate measurements of fuse resistance as measured in a fuseholder (for just one direction), indicating that the direction-related measurements were performed by touching the meter leads directly to the contacts on the fuse.

(d)Perhaps even contributed to by differences in the resistance of the measurer’s body, that would have been paralleled with the resistance of the fuse if he or she had fingers on the probe tips and/or the fuse contacts while the measurements were being taken.

(e)If Geoff’s comments about all wires being significantly directional are to be believed, then these differences would be totally swamped by both the resistances and the alleged direction-related resistance differences of the vastly longer associated wiring. In the case of mains fuses, that would include the power transformer and the power wiring in the component, as well as the power cord and the AC wiring in and outside of the house.

I’ll say also that the comments I provided on the HFT paper in the "Fuses That Matter" thread (linked to in one of my posts earlier in this thread) do nothing to provide confidence that these measurements were performed in a methodologically scrupulous manner, that would rule out the kinds of extraneous variables described in (b), (c), and (d) above.

Regarding the anecdotal reports Geoff refers to, such as those provided by various A’gon members in the current SR fuse thread, those are the one reason for which my mind remains somewhat open on this issue. Particularly given that some of those reports emanate from sources I consider to be particularly credible, such as Charles1dad among a few others. But while in those particular cases I certainly don’t question the reported perceptions, I also don’t rule out the possibility that subtle and non-obvious effects may have been in play which resulted in attribution of the perceived effect to something other than the variable that was actually responsible. Perhaps even differences in contact integrity.

If as Geoff indicated the case is indeed closed, I hereby submit a petition for "certiorari" to the highest judicial body having appropriate jurisdiction, namely the individual judgment of each reader of this thread, who can and will decide for themselves. :-)

Regards,
-- Al

One amplifier came in with one of these ’tuning’ fuses which was blown. Usually when the particular fuse location in question is blown, it indicates a service issue, but in this case the amp was fine- once a good fuse (we use Buss and Littlefuse for the most part) was installed. As this fuse was made in Germany, I suspect its the same fuse as Roger Modjesky must have encountered. Even though marked correctly the fuse was not up to its spec! So Roger likely has good reason to not recommend these fuses.

Since the installation of this fuse caused a customer to have downtime and the cost of shipping (about $170.00), I have to agree that these fuses can be problematic! While we are not saying they can’t be used in our gear, I am saying that you may experience fuse failures that are premature. So this aspect should be on your radar should you choose to install such fuses.

1.  Since it only occurred once, probability fuse not up to spec is low IMO. 
2.  Since it only occurred once, possible fuse worked as design and save the amp from damage.   I bet if you install another one, it will work.

Atmasphere, thanks for sharing your experience.

Al refers to them as anecdotal. I prefer to refer to them as evidence. It’s what folks observe, you know, hear. Folks think of seeing as observation usually, but isn't hearing observation, too?  t’s all part of the thing called the scientific method. We have a hypothesis, we test the hypothesis and we accept or reject the hypothesis based on ob-ser-va-tion. It’s actually remarkably simply. As I am fond of saying, it’s the preponderance of the evidence that counts. And there certainly has been a bunch of that, 

Mapman wrote,

"I was given a Synergistic Red Fuse to try. I tried reversing directions. Did not hear a difference. So by geoff’s logic that means there IS NONE. What a joke!"

There is an exception to every rule. Of course, there are any number of perfectly good reasons why you didn’t hear a difference. Shall we explore what those are? ;-)

Geoff,

Rational and Logical comes to mind :-)

Good Listening

Peter