by "Phil Allison" <philallison@[EMAIL PROTECTED]
>
Apr 28, 2008 at 12:18 PM
"Trevor Wilson"
> **UPDATE!
>
> I checked a bunch of the fuses. The ones which measured high were
'Ralmar'
> branded. I checked some branded (Littlefuse) ones and found them to be
5.3
> Ohms. A couple of unbranded ones in the bottom of the drawer (probably
WES
> ones) were 5.5 Ohms. The Ralmar fuses have been placed where they belong
> (in the trash). I also checked a Littlefuse M205 type at 4.7 Ohms.
** There IS a manufacturing problem with your 250mA fuses !!!
I found that some of my stock of low current fuses gave absurdly high
resistance readings too - if tested with a DMM or Bobs ESR meter.
After testing at the rated current, with a current limited PSU, the
fuse's
resistance value returned to normal.
Theory:
Low current fuses are made with resistance wire, not copper or tin wire
as
with higher current types.
Where the wire ends are soldered to the fuse caps, a high resistance joint
can form.
Applying a few volts breaks down whatever corrosion is causing this
resistance.
DMMs etc do not apply enough voltage to have any curative effect.
...... Phil
