The OP41 is an audio output pentode that is equivalent to the Mullard Pen4B. It requires an anode load of 3,500Ω and will produce 8.8 Watts.
The identification is etched into the dome.
Looking down into the valve the main electrodes can be seen. The anode is a cylinder with the suppressor grid within. The two inner grids are oval and the oxide coated cathode is flat across the face.
The classic envelope is 54 mm in diameter, and excluding the B7 base pins is 119 mm tall.
Reference: 1043. Type OP41 was first introduced in 1937. See also1937 adverts.
