by "Trevor Wilson" <trevor@[EMAIL PROTECTED]
>
Apr 28, 2008 at 01:08 PM
"Phil Allison" <philallison@[EMAIL PROTECTED]
> wrote in message
news:67kqg6F2p0hkrU1@[EMAIL PROTECTED]
>
> "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.
**Interesting theory. I'll dig a few out of the bin and see what happens.
Trevor Wilson
