Good comments from all the above.
If failure was at same position, it could be random but also a cause for some concern.
Also monitor the bias more frequently than Manley suggests to check that your amps can hold it there. Safer not to exceed the value whatever the sound, a bit lower the better for tube life. Also a question to the seller of what caps exactly were changed and why.
Tubes can go funny and not created equal. For me two failures in 1,5 years with no constant use is at the limit of unexpected.
G
If failure was at same position, it could be random but also a cause for some concern.
Also monitor the bias more frequently than Manley suggests to check that your amps can hold it there. Safer not to exceed the value whatever the sound, a bit lower the better for tube life. Also a question to the seller of what caps exactly were changed and why.
Tubes can go funny and not created equal. For me two failures in 1,5 years with no constant use is at the limit of unexpected.
G