VAC Phi 300.1 won't power on.

I'd start with checking the fuses.

One thread I read mentioned the "Sentry Circuit" which shuts down the amp if a tube goes bad to avoid damaging the amp.  Is anyone familiar with this circuit, and how to reset it? 

Agree with pdreher. Check the fuse.

Take a look inside the amp. A soft "pop" could be a shorted coupling cap. Look for a cap with white stuff coming out one end.

Don't stick your fingers in there! Use a wood skewer to poke around with!

Happened to me with my Phi 200 once.  Check the fuse in the back of the amplifier.

If you want a response from VAC, you have to call, email is not well attended to. They are very good at troubleshooting over the phone, I spoke to Keven 2 weeks ago before determining I needed to send my pre amp in. They have been exceedingly busy with audio shows as of late. Good luck!  But yeah, ck the fuse.

Problem solved - fuse!  Thanks all!