[keith49vj3]

All,  I just helped a friend rebuild a 48-475.  It sounds great now but it has a couple of minor issues.  When first turned on it sounds like a Jet aircraft engine starting up.  When turned on while cold you  hear a low frequency whine that keeps increasing with frequency until you can no longer hear it.  This only happens during the first minute or two of startup. My friend played it all day and he says there is also a mechanical hum coming from chassis and not the speaker. Could these problems be related?
Thanks,
Keith