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Solenoid - shorted turns.

N

N_Cook

Jan 1, 1970
0
Not where I've ever seen one before, the trigger actuator for power take off
in an audio cassette deck. Obviously overheating but no obvious burning ,
probably buried. Measures 4.1 ohm but by calculation for 38swg wire and
possible range of inner core diameter and layup packing factor between
regular Pi/4 and stagered layup optimum of (sq root 3)/2 comes out to be
range 16 to 43 ohm. So will have to countoff/rewind. 38 swg enamelled Cu
wire data 0.018 sq mm area and .776 ohm / m
I was exploring use of polyswitch / reset fuse MF-R110 , 5mm 1.1 amp hold
current in its PTC thermal properties to lay on the outside added in series
as a protector. In olden days of bulky VCRs there was 2 coils , the pull-in
and the hold, to avoid heat build up.
Anyway data for this particular type of small polyswitch , as I can see
being useful in other non mains fuse situations.
20 to 42 deg C, 0.2 ohm
66 deg , .3
92 , .4
100, .45
108 , .5
118 , .7
122, 1
123, 2.5
126 deg C, 11 ohms
then goes shooting off
 
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