Hi Everyone,
Sorry in advance for my newbie question. I'm not very well versed in tube amp design but am trying to learn.
I have a completely stock ST70 with 7199 tubes and original parts (except for the selenium rectifier). The 47 Ohm resistor connected to pad 9 blew on the PC3 while I was listening to it. It looks like the 620 ohm and 47 ohm resistor is a voltage divider to reference the EL34 Screen Grid, so I think this is the screen grid resistor?
In any case, it seems like one of my tubes probably ran away (I really don't know, the amp was running for about 12 hours straight at low volume, made a crackling sound in one channel and I ran to turn it off), and caused the 47 ohm resistor to blow.
First of all, is what I said above even true?
In addition to replacing the 47 ohm resistor, should I replace my EL34's? Could the 7199 also have caused this to blow? Since the EL34 screen grid is connected to the output transformer, do I need to worry about this too?
Again, thank you for your patience and for teaching me!
Gary
Sorry in advance for my newbie question. I'm not very well versed in tube amp design but am trying to learn.
I have a completely stock ST70 with 7199 tubes and original parts (except for the selenium rectifier). The 47 Ohm resistor connected to pad 9 blew on the PC3 while I was listening to it. It looks like the 620 ohm and 47 ohm resistor is a voltage divider to reference the EL34 Screen Grid, so I think this is the screen grid resistor?
In any case, it seems like one of my tubes probably ran away (I really don't know, the amp was running for about 12 hours straight at low volume, made a crackling sound in one channel and I ran to turn it off), and caused the 47 ohm resistor to blow.
First of all, is what I said above even true?
In addition to replacing the 47 ohm resistor, should I replace my EL34's? Could the 7199 also have caused this to blow? Since the EL34 screen grid is connected to the output transformer, do I need to worry about this too?
Again, thank you for your patience and for teaching me!
Gary