@artemus_5 consider folks who never previously built anything assembled all but a few of the 300,000 ST70s, the fact that most of them that came up on the used market sported their original (5AR4 and all) tubes, and the majority of that number still worked mostly fine even after all those many, many years.
Unless Bob's using too big a capacitor in the first position of the power supply, which WILL blow rectifier tubes with regularity, there's no need to sweat it. Just get another 5AR4. I recommend spending for a vintage tube for best sonics and reliability. After that, sit back, and enjoy.
Unless Bob's using too big a capacitor in the first position of the power supply, which WILL blow rectifier tubes with regularity, there's no need to sweat it. Just get another 5AR4. I recommend spending for a vintage tube for best sonics and reliability. After that, sit back, and enjoy.