03-17-2013, 09:07 PM
Jerry
I saw similar wattage in similar places in Philcos, but here how I went about it:
You have about 300V going to that 14K resistor (I took the voltage of the output amp plates), and then the 14K after filtering forks into 10K and 40K resistors. If we took the worst case (which it is not) where both 10K and 40K resistorts go to GND then we would get 8K in series with 14K, hence 22K total.
Now we take 300V square = 90,000 and divide it by 22,000 which will get us about 4Watts total dissipation.
But this is split between the 14K and 8K, so the 14K will get (4W/22)*14=2.5W.
At this worst case dissipation 5W is plenty.
PS. Make sure when buying resistor the datasheet rates it at full dissipated power, no cooling.
I saw similar wattage in similar places in Philcos, but here how I went about it:
You have about 300V going to that 14K resistor (I took the voltage of the output amp plates), and then the 14K after filtering forks into 10K and 40K resistors. If we took the worst case (which it is not) where both 10K and 40K resistorts go to GND then we would get 8K in series with 14K, hence 22K total.
Now we take 300V square = 90,000 and divide it by 22,000 which will get us about 4Watts total dissipation.
But this is split between the 14K and 8K, so the 14K will get (4W/22)*14=2.5W.
At this worst case dissipation 5W is plenty.
PS. Make sure when buying resistor the datasheet rates it at full dissipated power, no cooling.
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