[radio1]

My 70 does this, somewhat different, using the old globe Philco 27 osc tube the radio ramps up smooth, using a newer ST RCA 27 the radio goes through these clicks with a high raspy sound just before it settles and clicks in around 12 to 15 seconds. The older tube test just above 50% on a Knight emission tester, the RCA tests around 70%. Don't know if this is symptomatic of some other problem as of yet, but strange you mention it when I have a similar sound. Both tubes test okay on this type tester with no shorts or gas.