My Galaxian starts the game as soon as a credit is added. I've checked the repair guide and this fault is clearly discussed, however after changing the bad IC it works for a few times and then fails again.
Anybody here have an idea of what might be wrong? I'd like to send it off for repair (I lack time)
LMK.

I know this may be a stupid question, but could your player 1 start button circuit be grounded somewhere?

nope. I socketed the offending IC (and fixed the awful traces leading to it) and a new IC lasts a few games but then blows again. I've blown a couple to be sure.