[Ron Ramirez]

Philco never published a schematic of the 40-180 showing the 6J8G tube. You have to use the schematic showing the 7J7, and have a layout of the 6J8G connections handy.

The internal elements of the 7J7 and 6J8G are identical, and would appear so on the schematic if two versions existed (one showing a 7J7 and one showing a 6J8G). It is only where the elements connect to the individual pins (and grid cap in the case of the 6J8G) that differ. Both are triode-heptode converters.

I prefer the NJ7P tube database, results are below.

7J7: http://www.nj7p.org/Tube4.php?tube=7J7
6J8G: http://www.nj7p.org/Tube4.php?tube=6J8G

Notice that they are electrically identical - specifications are the same - and each tube contains a triode and a heptode in the same glass envelope! Again, the difference is in the pin layout.