When did they first arrive and do they always have an unusual body colour? There is a patent reference to 1977 but when would the first appearance in domestic equipment have been ?. Resistors that fail open circuit if a designed-in current capacity weak point is exceeded , fuse-fashion, not just the thermal limit of the body , so often no overheating discolouration to the body or surrounding board
The first ones I remember were in the dropper series on old televisions, they had a spring (like half a safety pin) soldered to the terminals. Do they count?
"N_Cook"
** Genuine "fusible "resistors with specific fuse current ratings are rare beasts - the only ones I know of were used by Yamaha in some of their 70s and 80s audio amplifiers and were all miniature wire wound types.OTOH - what are nowadays laughingly referred to as "fusible resistors" are simply "flame proof" resistors - typically ordinary 0.5W & 1W metal film types with a high temp, flame proof coating in lieu of the incendiary paint coatings normally used.
.... Phil
Way before 1977 !
Take a look at radio and TV sets from the late 50s and 60s. Big white or beige wirewound resistors in a ceramic housing, one of the leads spring loaded along the edge, low temp solder blob on the spring to keep the circuit closed.
Designed to cut open when the resistor's body reaches some 200 degrees Celsius / 400 degrees Fahrenheit.
(I think I can digg up a picture, if you want :-)
-- Kind regards, Gerard Bok
Fusible resistors have been common in the US for a very long time. They were used in the early solid state car radios to prevent damage when the germanium output transistors shorted. Probably started in car radios about 1959. They were used in place of a fuse in a lot of early line powered consumer electronics to prevent some idiot from bypassing a blown fuse.
-- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
colour?
in
Sorry, I should have said fusible resistors otherwise visually indistinguishable from conventional 1/3 or 1/2W, MO resistors. Grey bodied 1/3W and 1/2W Philips ones in a 1992 Farnell catalogue
e
quoted text -
Don't know about that exact type, but we were using a black coated 5W axial WW from, I think, Dale and it looked exactly like the normal 5W axial except the usual number ended in "F". It, presumably, used a weak point since it fused on overcurrent rather than overheating. That was back in the early '90s. As mentioned by others, the 'sand coated' "Fusistors" have been around at least since WWII.
Neil S.
As far as Philips NFR25 range came in after 1984 and before 1987. I was trying to gauge what sort of current surge would knock out a standard MO resistor without leaving any trace of overheating versus a proper 1/3W fusible resistor if it was likely to be around in 1990.
On 6/18/2010 7:35 AM N_Cook spake thus:
What's "MO"? Never heard this term applied to resistors before.
-- The fashion in killing has an insouciant, flirty style this spring, with the flaunting of well-defined muscle, wrapped in flags. - Comment from an article on Antiwar.com (http://antiwar.com)
On 6/18/2010 1:08 PM David Nebenzahl spake thus:
Hmm, let me guess at my own question: metal oxide?
-- The fashion in killing has an insouciant, flirty style this spring, with the flaunting of well-defined muscle, wrapped in flags. - Comment from an article on Antiwar.com (http://antiwar.com)
Fusistors have been used in test equipment for many years in the input section. Fluke uses them in all the meters. I know, I've replaced many in the past.
Shaun
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