Pa_max and Ps_max are interdependent: the Philips datasheet provides a derating chart (page Q) showing that maximum 12 W anode dissipation and maximum 5 W screen dissipation cannot be achieved simultaneously.
The screen grid series resistor must have a minimum value of 2.2 kOhm to avoid Barkhausen oscillations.
Rg1 max is 0.5 MOhm normally, but 2.2 MOhm is permitted for line output tube application only.
PL36 is the 25 V / 300 mA series-heater version; 25E5 is the American 25 V heater equivalent. These are not pin-compatible drop-in replacements due to different heater requirements.
An earlier Mullard tube also designated 'EL36' was an audio output pentode (the EL6 re-based to Octal) with different characteristics (Pa_max = 18 W, gm = 14.5 mA/V, ra = 20 kOhm). The Philips line-output EL36 superseded it and is the standard type.
Triode-strapped data sourced from Tom Schlangen's 'Pentodes Strapped as Triodes' (2009) measured data table and Turner Audio amplifier design page (https://www.turneraudio.com.au/2323-triode-integrated-6cm5.html), not from the manufacturer datasheet.
Pin Layout — Octal
1Internal Connection
2Internal Connection (Cathode/Suppressor)
3Heater
4
Socket-Compatible Tubes ⚠ Not electrically compatible