"Trevor Wilson"

I assume we are all familiar with those dreaded fusible resistors. I used
to get caught out with those buggers. Even quite low values (47 Ohms) and
even when not subjected to high stress, the buggers would go high (usually
to around double the indicated value). Not high enough to cause major
faults, but high enough screw up the operation of whatever they've been
installed in.


** The vast majority of "fusible or "flameproof " resistors are simply
ordinary metal film types with a non flaming coating.

Take any low value, MF resistor and subject it to 10 to 20 times it's
nominal power rating - it will go open quick smart, usually leaving a
black mark on the surface. At lower overloads, the same MF resistor will
smoke and flame alarmingly.

If you see one that has gone high in value it has very likely been subjected
to a brief current surge just below what will cause it to open.


..... Phil