Bench tool

Bleeder Resistor & Discharge Time Calculator

Size a bleeder resistor to guarantee filter caps discharge to a safe voltage in a known time, or check how long an existing bleeder takes.

⚠ Filter caps hold a lethal charge after the amp is switched off — bleeders reduce the risk but don't replace verifying with a meter before you touch anything. Never assume a cap is discharged just because time has passed.

Size a Bleeder Resistor

Enter your B+ voltage, the total filter capacitance the bleeder sits across, and how fast you want it discharged — get back the resistor value and the wattage it needs to survive continuously.

V
V
sec
Bleeder resistor
221 kΩ
exact: 221,562 Ω
Continuous power0.914 W
Recommended rating2 W

The bleeder is connected across the B+ rail permanently, so it dissipates this power the entire time the amp is powered on — not just during discharge. Rate it generously; a bleeder that opens or drifts high defeats the whole point.

Check Discharge Time

Already have a bleeder installed? Enter its value and see how long the caps actually take to reach a safe voltage.

V
µF
kΩ
V
Time to reach safe voltage
59.6 sec
Continuous power0.92 W
Recommended rating2 W

This models the bleeder discharging the cap on its own (worst case, amp off, nothing else drawing current). In a real amp, tube heaters and standby circuits can pull the actual time down further — this number is your upper bound.