Series-heater (150 mA) version of the EF94/6AU6. Electrically identical sections — only the heater voltage/current differs (12.6 V at 150 mA vs 6.3 V at 300 mA).
The H-prefix (150 mA series) is relatively uncommon — most series-string receivers used either 300 mA (P-prefix) or 100 mA (U-prefix) heater chains.
Suppressor grid (g3) is internally connected to cathode.
Vhk_max is 100 V DC (cathode positive relative to heater).
Pin Layout — B7G
1Control Grid
2Suppressor Grid (g3,internally connected to cathode)
3Heater
Socket-Compatible Tubes ⚠ Not electrically compatible