Do you have the OE Power Cord?
if you do plug it is and see if this solves the issues. If it does problem solved and move on, if not then you need professional help.
10 gauge power cord. Too much power for tube amp?
Tube amplifiers tend to be sensitive on incoming voltages. Is there a chance a bigger gauge power cord like 10 gauge may not be a good thing?
My amplifier tends to shut down occasionally upon start up. maybe moving to a higher gauge might be better. Does it matter?