Flameproof resistor sources?
 

Hey Group,
Does anybody have sources for lower value flameproof resistors.
You know... like the quarter watters that frequently burn in defective audio equipment.
MCM used to carry quite a variety but their value selection is getting thin.

Thanks

Jim

Mouser has some in stock.

http://www.mouser.com/Passive-Components/_/N-5g73Zscv7?Keyword=flameproof&FS=True

Look for "metal film" resistors.

General suppliers like Mouser will have them.

Flame proof types are generally metal oxide resistors IMLE and should be clearly described as such as not all MO types are flame proof.

Some metal films will burn, and carbon films definitely do - sometimes quite spectacularly. :hot: :D

The datasheet I have for metal film resistors state the following:
- Vishay BC NFR01 (1W), NFR02 (2W), NFR03 (3W) are non-flamable
- Vishay Dale CMF and CMF RN series are flame 'retardant'
- Yageo RSF series are flameproof (oops: metal oxide, not metal film)
- Yageo FRM series are flameproof (metal film, 5% though, see Digikey catalogue page 2039)

Note: flame retardant means that the flame will extinguish itself if no energy is added, which is not the same thing as flameproof (not burning at all).

Not surprisingly, many flameproof resistors (not Dale) are also 'fusible' type resistors.

Other data sheets (for metal film) I have do NOT state flameproof or the like for:

- Vishay Beyschlag DA-01 and DA-02
- KOA Speer MF, MFS, RK series
- Ohmite HPW, WHN, WNM series
- Panasonic EROS2, ERO25 series
- TT TC, Welwyn series
- Vishay BC MRS16, MRS25 series
- Vishay BS SFR16S, SFR25, SFR25H series
- Xicon MF, RC series

You can find all of the above at the usual large webshops.

I don't know what your application is, but if it is for the usual 'flameproof fusible' type resistors in the output driver circuits, then installing a quality overrated (i.e. 1W instead of 0.25W) resistor will do the job (please do ignore this statement if it concerns high voltage circuits in tube amps).

EDIT: I should be more carefull saying things like that; if the amp manufacturer put fusible resistors in a driver circuit, then they are there to protect the transistors against overcurrent. But if you are in the process of rebuilding the amp to a more decent standard, by replacing the driver trannies with much better ones anyway, then you can safely replace the initial fusible resistors with higher rated regular (quality) metal film resististors, in my humble opinion.

Yep - do the job of not burning open circuit when you want it to (due to the higher wattage) - use 0.25w or possibly 0.5w but you are asking for trouble if you go up to 1w - just my 3 ha'pence worth.