[electroking]

Hello andy,

Thanks for the reply, here is my attempt at calculating the resistors. However,
I found that the resistors would dissipate almost as much as the rest of the electronics,
so I thought there was an error. What do you think?


First get the total power consumption from the data plate. Let's call this P_tot.

The heaters are drawing 600 mA at 117 V, that is 70 watts.
Define P_DC = P_tot - 70.

P_DC is essentially generated by the 264 V supply, so the power supply
current is essentially I_DC = P_DC/264.

Now you want resistors that will drop the voltage from 475 to 264 while
passing I_DC, that is 2R = (475 - 264)/I_DC, or

R = 105.5/I_DC.

Numerical example: assume total power is 140 W. Then P_DC = 70 W,
I_DC = 70/264 = 0.265 A and R = 398 ohms or roughly 390 ohms.

Each resistor will dissipate 398*0.265*0.265, that is 28 W, that is a total of
56 W.

P.S. 475 is the voltage measured at the B+ bus without resistors, while
264 is the nominal value from the schematic.