18Watt.com

I'm working on a mini amp without much room inside and I want to use the unsused pins on the 12AX7s and EL84s as tie points. How can I find out what the limit is for these unused pins?

For example, I want to use pin 8 on the EL84s as a tie point for the junction of the blocker cap, 1k grid resistor and 330k resistor to ground at the PP output.

Second use would be pint 9 on the 12AX7 as a tie point in the split PI for the resistor network/second blocking cap.

Thanks!

There are no unused pins on a 12AX7, pin 9 is a heater connection.

On the EL84 tube, pin 8 is sometimes used as an internal connection, so don't use that one as a tie point either.


RWood

If you need a tie point, one way is to mount one of these on one of the screws holding the socket in:

Alexo wrote:There are no unused pins on a 12AX7, pin 9 is a heater connection.

OOps...Duh! Scratch that.....

RWood wrote:On the EL84 tube, pin 8 is sometimes used as an internal connection, so don't use that one as a tie point either.


RWood

Probably goes for pin 6 too, huh?

Look at several tube spec sheets. When I look at one for the EL84 it says pins 1,6 and 8 are i/c, which means internally connected. In the real world it means that sometimes they are and sometimes they aren't. IMHO, it is always best to not use them.

As suggested, a terminal strip is the best solution in a tight space. A lot of the lower power amps of the 40s, 50s and 60s were all point to point with just a few terminal strips. Then again many boutique amps use merminal strips instead of any board!