08-19-2022, 02:20 PM
I'm part way through the electrical restoration of a 41-255, fixing some previous old repairs, etc., and I see some indications of heat and possible arcing on the multi section Candohm style resistor (pic below) labeled 61 (33-3393) in the power supply section of the schematic (below). The resistance values are close to those listed but I'd like to replace it with discrete resistors, though I need a reality check on power dissipation (no info on the parts list or the 1942 Philco parts catalog...). I've sniffed here and over at the ARF but find varying information.
The filament string has its own winding so not a factor; the 84 rectifier is supposed to be good for ~60ma. Is it safe to assume worst case is 60ma through each section of that multi wire wound? For each section of ~150 ohms, 30 ohms, and 15 ohms, I come up with drops of ~ 9V, 1.8V, and .9V, so I figure dissipation of ~.54w, .1w, and .05w. I already have some 3w and 1 watt resistors on hand and figure that should be adequate. Just looking for a reality check here to make sure I'm not wildly underestimating what I need, since the original resistor seems like a huge overkill for that dissipation. Unless of course Philco just took advantage of what was on hand or perhaps it was easy to adjust the taps for any need, regardless if the required dissipation required was minimal.
The filament string has its own winding so not a factor; the 84 rectifier is supposed to be good for ~60ma. Is it safe to assume worst case is 60ma through each section of that multi wire wound? For each section of ~150 ohms, 30 ohms, and 15 ohms, I come up with drops of ~ 9V, 1.8V, and .9V, so I figure dissipation of ~.54w, .1w, and .05w. I already have some 3w and 1 watt resistors on hand and figure that should be adequate. Just looking for a reality check here to make sure I'm not wildly underestimating what I need, since the original resistor seems like a huge overkill for that dissipation. Unless of course Philco just took advantage of what was on hand or perhaps it was easy to adjust the taps for any need, regardless if the required dissipation required was minimal.
