If this was a tube or speaker issue it is rare they all fail at the same time.
Swapping speakers, or tubes should help diagnose, but if the problem is systemic, it's possible the regulator on the PV 10 has failed, or one of the cascaded diodes has.
I like the PV 10, but the thing the later generations did well was to split up the voltage regulator into multiple sections so the chances of one regulator failing was rarer, not to mention offering better power supply isolation.
Swapping speakers, or tubes should help diagnose, but if the problem is systemic, it's possible the regulator on the PV 10 has failed, or one of the cascaded diodes has.
I like the PV 10, but the thing the later generations did well was to split up the voltage regulator into multiple sections so the chances of one regulator failing was rarer, not to mention offering better power supply isolation.