Resistor in Power Supply Input

On a sunny day (Wed, 20 Dec 2006 15:55:51 +0000) it happened nospam wrote in :

Ah thank you, did not know that. I see that at 32 rated wattage it still takes 30 seconds to OC (else longer). So for a 1/4 W type it takes 8 W.

"Jan Panteltje"

Comedy is not dead.

....... Phil

Standard metal oxide resistors are power resistors and are in the same category as standard wirewound resistors. If you used a 2W MO resistor it is no wonder the pcb was charred.

You obviously didn't read my first post where I put the link

Note that Micron FN192R7J is described on page 7 as a FUSIBLE metal oxide resistor. I admit the data sheet is a bit confusing because the part numbering system at the top of the page designates the resistor as starting with FRN or FRW. This seems to conflict with the the part numbering system at the bottom. FN192R7J actually translates to;

FN1 Fusible Resistor Metal oxide

While carbon film resistors do fuse they are not designed for this purpose. The problem with using carbon film is that short term overloads over a prolonged period will eventually lead to increasing resistance which will present other symptoms.

Just a quick look at the MF-R series shows these are resettable resistors (essentially a PTC resistor). My preference would be for a fixed value fusible resistor equivalent to the original.

Meritek USA make them although 4R7 is their lowest in 0.25W but this would be suitable for your application

Micro Ohm is another