Complex sentence: This instrument was overhauled twice, in 1927 and 1956, but, by the time it was last heard in 1983, its state of repair was such that it had to be taken out of use.
Split into simpler sentences: This instrument was overhauled twice, in 1927 and 1956. But by the time it was last heard in 1983 its state of repair was such that it had to be taken out of use.