The bias on my st70 always drifted up and down during the usage.
I didn’t know why it did that. However, after replacing all the original grid resistors with modern resistors yesterday, the bias is no longer drifting. I found one of the original carbon resistors becomes open circuit after heating up. Quite strange.
I didn’t know why it did that. However, after replacing all the original grid resistors with modern resistors yesterday, the bias is no longer drifting. I found one of the original carbon resistors becomes open circuit after heating up. Quite strange.
Whenever the power mains voltage varies, the bias supply voltage varies.
I bought a bunch of LCF802/6LX8 tubes in a deal. It has the same pinout as 6GH8.
This thing looks quite linear on paper. It is noticeable quieter (/less hum) than 6GH8.
As my circuit is modded (as OP) to accept all kinds of triod-pentode tube. Not sure how it works on the original ST70.
This thing looks quite linear on paper. It is noticeable quieter (/less hum) than 6GH8.
As my circuit is modded (as OP) to accept all kinds of triod-pentode tube. Not sure how it works on the original ST70.