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

On 18/06/2010 12:56, N_Cook wrote:
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"

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


** 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

On Fri, 18 Jun 2010 12:56:09 +0100, "N_Cook"
wrote:

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 ?.

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

N_Cook wrote:

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


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.

Gerard Bok wrote in message
...
On Fri, 18 Jun 2010 12:56:09 +0100, "N_Cook"
wrote:

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 ?.

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


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

On Jun 18, 7:35*am, "N_Cook" wrote:
Gerard Bok wrote in message

...





On Fri, 18 Jun 2010 12:56:09 +0100, "N_Cook"
wrote:

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 ?.

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

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- Hide quoted text -

- Show 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:

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

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:

On 6/18/2010 7:35 AM N_Cook spake thus:

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

What's "MO"? Never heard this term applied to resistors before.

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)

"N_Cook" wrote in message
...
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


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