AISIP,
You should call Kirk at Cary Audio and explain which tube positions are not getting heater voltage. Chances are good that there is a fuse associated with that group of tubes.
In general tubes rarely all fail at the same time. So the catastrophic failure of three tubes is very unlikely. Normally there is one portion of the power supply that provides the heater voltage and one that provides B+ or High Voltage. I find it unlikely that there is a power supply failure if 9 of the 12 tubes are getting heater voltages.
With all that said you are most likely looking at a fuse or at very worst a burned resistor or resistors which in some designs like Audio Research act as fuses. Kirk should be able to help you further. Do be careful if you open the amp up. The DC caps in a tube amp can hold a charge for many days in some designs.
You should call Kirk at Cary Audio and explain which tube positions are not getting heater voltage. Chances are good that there is a fuse associated with that group of tubes.
In general tubes rarely all fail at the same time. So the catastrophic failure of three tubes is very unlikely. Normally there is one portion of the power supply that provides the heater voltage and one that provides B+ or High Voltage. I find it unlikely that there is a power supply failure if 9 of the 12 tubes are getting heater voltages.
With all that said you are most likely looking at a fuse or at very worst a burned resistor or resistors which in some designs like Audio Research act as fuses. Kirk should be able to help you further. Do be careful if you open the amp up. The DC caps in a tube amp can hold a charge for many days in some designs.