Hello, I am Mario from Italy.  I have an electric Weber Duo-Art built
in 1923.

I have some problems in the repetition test: during the performance of
complicated rolls, some high notes are missing.  (The same notes which
have problems in the repetition test.)   At zero level the bass and
medium play but high have problem to play.

Can you help me?  Is a problem of regulation of the valves?  Must
I replace tubing?

Best Regards
Mario Solimbergo