Complex sentence: The other band members decided that neither McCartney nor Griffiths were suitable lead guitarists, so when George Harrison joined the band they suggested that Griffiths buy an electric bass and an amplifier, but he could not afford this.
Split into simpler sentences: The other band members decided that neither McCartney nor Griffiths were suitable lead guitarists. When George Harrison joined the band they suggested that Griffiths buy an electric bass and an amplifier but he could not afford this.