Valve failure on Icon Stereo 60

[Pupp]

Think one of the large valves (inner left) on my Icon Stereo 60 has failed this eve... loud pop, then valve core glowing much brighter orange (with no usual blue plasma glow on the outer). Can replace the tubes ok but anyone know if it likely to have taken anything else with it? Been using valve amps for years and never had one do this before

[Pupp]

Well, for the sake of completeness if for no other reason, bit of investigation with a meter and an infrared thermometer yesterday revealed that the slow-blow fuse for the cathode on the suspect valve had blown but the valve itself 'seemed' ok... the heater was still working but the valve was not emitting so temperature was about 100dec C below the others and could measure no voltage on the bias circuit.

So, new fuse sourced installed and a very wary turn-on... all seems ok again; even temps, bias voltage, and plasma restored. Can only assume it was a mains surge that did it and the fuse did it's job. Happy not to be shelling for a repair bill anyhoo