#4710 safety valve

[Caustic]

Safety Valve - 27R is smokin' hot

From a quick peek at the schematics, it’s in series with the heater filament which is speced as max 150 mA at 12.6 V so simplifying a bit total series resistance is 27 + 12.6/0.15 = 111 ohms which corresponds to 12/111 = 108 mA through the circuit from the −12 V rail, and the 27 ohm sees 27×(12/111)^2 = 0.32 W which is above the specs for a 1/4 W resistor. It’ll probably survive (the watt limits are set for a high ambient temperature) but it’ll be hot. You could replace it with a 1/2 W or 2-4 l…

@fredrik suggests that the 27r should be more than a 1/4 w resistor. So either a 1/2W or you can put a few resistors in series.