VAC Phi 300.1 won't power on.

Problem solved - fuse!  Thanks all! 

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.

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

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

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.

Agree with pdreher. Check the fuse.

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? 

I'd start with checking the fuses.