Valves.....

MikeDearing

I've used tube amps all my musical life...  (actually that is a lie, I do own a JC and use that on occasion) but  I own quite a few still these days, and I have them serviced and biased regularly... however just recently I've been blowing el84s and.... unheard of ecc83/12ax7 pre amp valves....!   This can be either of the three valve "brands" we all use regularly... so it must be down to quality of manufacture - any thoughts? I have a couple of old amps that are still on their 1960s and 1970s valves that seem to show no sign of giving up other than being a bit jangly..    one common denominator  is that it seems to be smaller wattage kit.. so the valves may be closer to peak...and this is happening across the board... both pcb and turret hand wired 

ecc83

Are you able to safely check your mains voltage? It will almost certainly be 240V but could be as high as 253V and still be "legal" and quite possibly even higher.

Not that excessive mains volts should really impact on valve life short term, I have tried blowing up valves on test with overvolts on the heaters and they stand many, many time their rating for ages. In the old series heated B&W tellies the valves, some were ECC81/82s, glowed alarmingly brightly at every start up and yet heater failure was very rare, as indeed was valve failure overall except for line stage power valves and even then 2-3 years of 6 hrs per night 7d.a.w. could be expected.

I think you are just unlucky and have happened on a bad batch.

Dave.