Resistor network in half bridge rectifier
The resistors are there to cut the inductive spikes when D022 and D023 are reverse biased.
 The parallel-serial is to minimize the effect of a failing resistor and also to split the voltage across resistors with lower voltage rating. 

The overall resistance is Rt = 680k * 10 / 2 = 3.4M

Voltage per resistor Vr = 0.1 *V 

In case of a failing resistor

Rt =680k + 680k * 9 / 2 = 3.7M

Voltage over the remaining resistor

Vr = V * 680 / 3700 = 0.18 * V