"N_Cook" wrote in message
...
Arfa Daily wrote in message
...


"N_Cook" wrote in message
...
I have one in front of me labelled
UTM 210-9 25435,3 watt probably Russian and can find no info
Like the standard pillar white/grey ceramic resistors but instead of
the
wire returning down the flute of the ceramic there is a sprung join set
in
the flute with bismuth solder or something. Anyone know a generic name
for
this type of thermal cut out resistor or a maker name ?
Other than the opening temperature must be greater than the sustained
power
rating temp of the resistor and lower than standard solder, anyone know
what
sort of safety cut out temperature?



Back in the day when I was a TV engineer, they were very common, and
known
as 'spring-off resistors'. Often used to be used in the feed to the HOP
stage, and would spring open when the HOP valve failed. They were usually
re-soldered with what we knew just as 'high melting point solder'. I've
no
idea what actual temperature the stuff was, just that it was issued to
us,
a
few feet at a time, for re-soldering these devices. The Adcola irons that
we
used (about 50 watts, as I recall ??) struggled a bit with it, but were
ultimately capable of making the joint quite nicely.

Arfa


Are you saying it was somehow solder that needed a lot of heat rather than
a
lot of temperature?



Dunno really. No. I think I mean that it needed a lot of temperature. The
Adcola, with its solid copper bit, certainly produced enough heat at the
tip to handle a small job like resoldering that spring, but it did have a
little difficulty taking the solder to a 'full flow' consistency, so
probably didn't have quite the temperature required. Remember that this was
nearly 40 years ago, when a TV engineer's soldering iron was little more
than an electric poker ...

The solder was just designated "HMP" for high melting point, and as I
recall, was a little greyer looking on the reel than 'standard' solder.

Arfa