Pins on the KT66

[Lynxtrap]

This is a newbie question I guess, but why is there one more pin on KT66 than on 6L6GC? I think it's pin 1.

[rdjones]

This is a newbie question I guess, but why is there one more pin on KT66 than on 6L6GC? I think it's pin 1.

My guess is that they use the same base as other octal tubes in the same series such as KT77, KT88, and possibly EL34.
On the EL34/6CA7 pin 1 is used for the suppressor grid (G3) and connected externally.
On other similarly based tubes (including 6L6s) the suppressors are connected internally to the cathode/pin 8.
On the old metal shell 6L6 pin 1 was connected to the shell, but this was done away with on the glass tubes.

The GEC data sheet for KT77 shows pin 1 - "NC" meaning no connection, pin 6 is "NP" meaning no pin.
For the KT66 pin 1 is labeled "IC" which is internal connection, and for this reason it might be a good idea to ohm it out to the other pins to make sure.
Generally pin 1 can be grounded.

See other recent discussion about pin 1 issues, https://tubeamparchive.com/viewtopic.ph ... torder=asc

Someone else may know more about your specific tube than me.
What brand of KT66 is it ?


rd

[Lynxtrap]

They are Gold Lions, the new ones.