"N_Cook" wrote in message
...
Anyone any experience? Coil is fine. This is almost hair-fine
phosphor-bronze ribbon suspension , not hairspring and jewels. A ribbon,
top
and bottom, holds the coil frame and passes current. Each ribbon is
soldered
to the frame then passes through a hole in the offset-rotatable anchor ,
passes over the rounded edge of an open end of a U-shape of manageable
size
phosphor bronze spring , and soldered along the arm of that spring. The
solder point to the frame has failed from a jar / knock. So both U springs
are now opened to a V in comparison. I have tried solder to the end of the
fine ribbon and the stub on the frame, both take solder fine but not
joined
up yet. There is enough length of fine ribbon on the broken side to
resolder
to the coil frame , pass thru the hole and anchor off , on its u-spring
anchor farther along than originally.
But how to bring the open-U springs back to proper U before soldering the
anchor point. A matter of making a jig to compress or some sort of
external
spring over them ? And of course I've not seen a functioning movement. I'm
assuming setting up as U and then opening out a bit with the jigs removed,
or would the jig need to compress to more than U and then open out to U
with
jigs removed, normal use.
Pushing down on the spring of the good end and letting the coil frame
drop,
with gravity, it seems to be centrally aligned over the pole piece, when
the spring is a proper U viewed on side.
Where would one find , even robbing, short lengths of such rbbon if it was
required?



A couple of years back, a colleague gave me a professional Ferrograph audio
test set. This has a large format precision meter on the front, which has
the same vertical 'twisty' ribbon as the coil / needle suspension scheme. It
was broken when I got it. As there was little chance of being able to get a
replacement movement, I figured that repair was worth a go. As I recall
(it's been a while ago now) I simply fed the wire back through the hole in
the U-frame and held the frame in tension pushing down on pointy tweezers in
one hand, whilst using the soldering iron in the other hand. I had
pre-tinned both the wire and the frame, and simply bent the end of the wire
over with the tip of the iron, whilst letting a small 'blob' of solder
previously fed onto the iron's tip, flow into the joint. I was absolutely
amazed when I let go of it all, and blew on the pointer. It went from one
end of the scale to the other, as smooth as you like. No issues with
centreing or sensitivity or whatever. I seem to think that I struggled
slightly to get a good zeroing action from the zero offsetting screw in the
perspex cover, but I did manage it in the end. I can't remember why, or how
I got it to zero in the end, but I did, and it has remained correct since.
The unit is in daily use, so it has been an effective and long-lasting
repair.

Make no mistake, it was a delicate and fiddly procedure, with lots of
holding of breath and magnifying glasses and so on, but quite do-able for
the likes of you who enjoys challenges like this. Go for it. You've nothing
to lose.

Arfa