When inspecting the horn, I found that there was no "pop" when a valve slide is pulled before depressing the piston except for a very slight sound on the 4th valve. Also, when pushing slides back in, they don't get harder to push as they go in, leading me to believe that there is little to no compression available in the valves. This is the case on all 4 valves. Every slide on the horn moves freely with no hang-ups.
So I guess I'm looking for suggestions at this point. The eBay listing said "Good valve compression." Is there a better or more proper way to check this out?
I'd rather keep the horn if feasible, so what is a ballpark price estimate on a valve rebuild if necessary?
Thanks for any and all information. Here are some pictures...












