Type of ceramic wirewound resistor?

[Arfa Daily]

"nesesu" <neil_sutcliffe@telus.net> wrote in message
news:8b8b00d5-77b4-463e-8bc6-3d43637d602a@w23g2000vbx.googlegroups.com...

On Oct 13, 5:58 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
snip

I must be missing something here , what is the point of the spring
off
disconnect?

It opens the resistor, and removes power from the overload condition
that
it's there to protect against ...

Arfa

But not if you "weld" it shut with high melting point solder

What are you saying exactly ? That 'high melting point' solder was not
what
was originally used to hold it shut by the manufacturers ? Are you
suggesting that a company the size of Rediffusion, who designed their own
TV
sets making use of these devices, then went on to encourage their
(extremely
well trained and well thought of in the trade) engineers, to execute some
kind of bodge repair on ones that had opened ?

No, of course they didn't. If that material is what central stores
supplied
to the branches for remaking the spring connection, then I think you can
be
pretty sure that it was appropriate for the job. Presumably, as you found
it
necessary to ask what one of these resistors was in the first place, you
have no experience of them, contemporary with the time that they were
commonly in use ?

Arfa



- Hide quoted text -

- Show quoted text -

Perhaps N-Cook was thinking of the similar over temperature cutouts
used to protect transformers such as used in Philips Tape recorders
that used a very low temperature 'solder' to hold the spring
connection together.
This type of 'fusable link' has been used for well over 100 years and
uses very carefully formulated alloy as the sensor to operate at
remarkably precise temperatures. The fire sprinkler head is one of the
earliest mass produced applications of this technique.

Neil S.

Yes, agreed, but Mr Cook is very well aware of those, and the standard
advice of not to try to repair them for precisely the reason that it is a
very low melting point alloy that is originally used. However, the
spring-off resistors were designed to be resettable by resoldering. The
principle is not quite the same as the transformer thermal fuses, as with
the case of the spring-offs, the resistor element is designed to get hot,
and conduct the heat into the joint, via the thin wide conductor that is
closely fixed to the resistor's ceramic body

Arfa

 

[N_Cook]

nesesu <neil_sutcliffe@telus.net> wrote in message
news:8b8b00d5-77b4-463e-8bc6-3d43637d602a@w23g2000vbx.googlegroups.com...
On Oct 13, 5:58 pm, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:

snip

I must be missing something here , what is the point of the spring
off
disconnect?

It opens the resistor, and removes power from the overload condition
that
it's there to protect against ...

Arfa

But not if you "weld" it shut with high melting point solder

What are you saying exactly ? That 'high melting point' solder was not
what
was originally used to hold it shut by the manufacturers ? Are you
suggesting that a company the size of Rediffusion, who designed their own
TV
sets making use of these devices, then went on to encourage their
(extremely
well trained and well thought of in the trade) engineers, to execute some
kind of bodge repair on ones that had opened ?

No, of course they didn't. If that material is what central stores
supplied
to the branches for remaking the spring connection, then I think you can
be
pretty sure that it was appropriate for the job. Presumably, as you found
it
necessary to ask what one of these resistors was in the first place, you
have no experience of them, contemporary with the time that they were
commonly in use ?

Arfa



- Hide quoted text -

- Show quoted text -

Perhaps N-Cook was thinking of the similar over temperature cutouts
used to protect transformers such as used in Philips Tape recorders
that used a very low temperature 'solder' to hold the spring
connection together.
This type of 'fusable link' has been used for well over 100 years and
uses very carefully formulated alloy as the sensor to operate at
remarkably precise temperatures. The fire sprinkler head is one of the
earliest mass produced applications of this technique.

Neil S.

+++++


Someone upthread mentiond a currently available type of them
http://www.vishay.com/docs/21008/kk.pdf
page 41 top left has a spring open view of the sprung type
and top right of p42 has the derating plot showing the maximum operating
temperature of 150 degrees for the spring type , compared to 350 degrees for
the non-safety, plain vanilla ones