Today a thumb valve spring snapped on a student’s Conn 8D during a lesson. Obviously, we had to take a break to assess what happened, and to determine if I could do the repair myself or if a trip to the repair shop was in order. While we didn’t have an identical replacement part, I was able to fashion a workable solution from existing materials, see below.
The actual replacement part looks like this (image obtained from https://bandrepairparts.com/store/brass/conn_brass/conn_frenchhorn/2185-spring/)
I did not have a spring shaped like this in my drawer of replacement parts, but I did have some generic valve springs, as shown below:
Comparing the two, I was able to fashion something close using wire cutters and needle-nosed pliers. First I cut the spring roughly in half with wire cutters:
Then I used the pliers to shape the spring into something that looked close to the original:
It isn’t a perfect fit, but after a little fiddling and bending the sharp spring edges down, it is functional. See picture and video below.

Not bad for a day’s work, and this should work nicely until a repair technician can replace the part. Do you have some horn DIY stories to share? Feel free to comment below!