The following article contains an answer for the question: Who was replaced by John Lightman? , can you please find it? 

The frustration at #1 Record's obstructed sales contributed to tension within the band. There was physical fighting between members: Bell, after being punched in the face by Hummel, retaliated by smashing Hummel's new bass guitar to pieces against the wall. Hummel took revenge at a later date: Finding Bell's acoustic guitar in the latter's unattended car, he repeatedly punched it with a screwdriver. In November 1972, Bell quit the band. When work continued on songs for a second album, Bell rejoined, but further conflict soon erupted. A master tape of the new songs inexplicably went missing, and Bell, whose heavy drug intake was affecting his judgment, attacked Fry's parked car. In late 1972, struggling with severe depression, Bell quit the band once more, and by the end of the year Big Star disbanded.
After a few months Chilton, Stephens, and Hummel decided to reform Big Star, and the three resumed work on the second album. The title chosen, Radio City, continued the play on the theme of a big star's popularity and success, expressing what biographer Robert Gordon calls the band's "romantic expectation". As Hummel put it,
This was probably pretty lame, but in those days putting any word in front of the noun "city" to sort of emphasize the totality and pervasiveness of it was just a way of talking people had. If someone suggested going to a store but you had gotten a bad deal there you might say, "Oh no, that place is 'rip off city'." Calling an LP Radio City would be kind of wishful thinking. I mean we hoped it would be played on the radio a lot, making it "radio city". Of course it didn't pan out that way... Stephens recalled: "Radio City, for me, was just an amazing record. Being a three-piece really opened things up for me in terms of playing drums. Drums take on a different role in a three-piece band, so it was a lot of fun. [...] Radio City was really more spontaneous, and the performances were pretty close to live performances."Although uncredited, Bell contributed to the writing of some of the album's...

Hummel