Am 02.05.2011 11:30, schrieb N_Cook:
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?

First try to attach the ribbon to the frame. You might want to remove
the magnet first (if it isn't a core magnet type meter).

Remove the solder from the U-spring, especially near the open end with
solder sucking wick.

You have to press down the spring at the broken side more than the final
position so it will pull the other side into position one it's released.
You have to try that out. Too few tension is just as bad as too much
tension, because the frame wouldn't be in the right position then.

Solder the ribbon to the U spring near the turn of the U. Release the
spring, check if the tension is right (axial position of the frame). If
it is, you can now slightly adjust the axis of the frame now by pushing
the ribbon left or right. Now fix the ribbon near the open end of the
U-spring. Check that the pointer moves smoothly over the whole range by
slightly blowing at it.

Re-attach the magnet/scale (if removed).

Check equilibration (set the pointer to about 25% of the range and check
that it doesn't move when the meter is tilted back/forth; repeat for 75%).

Set the pointer to zero. Check sensitivity. If you can adjust
sensitivity at the electronics, do so. Else you have to move the
magnetic shunt (small iron strip at the magnet) to adjust sensitivity.

Markus