Sixth, solder diodes D12 and D13 and then solder resistors R5 and R6 followed by capacitors C15, C16, C17, C18, C19, and C20. Now solder green LED D14 and resistor R7 followed by terminal block K4. Connect a transformer or variac to the terminal block K3 again and measure the voltage produced by the left channel of the power supply (at the terminal block K4) as a whole. If you applied 12 Volt AC to the terminal block K3, the power supply should deliver about 17 Volt DC at the terminal block K4.
This error is duplicated in the instructions for both the left and right filament supplies in the Frigate manual.