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Philco 90 WW resistor question
#3

radioroslyn: I was going over your results and it seemed that a 20 watt resistor would much more than needed, and physical size also.  I attempted to do some calculations to see what I came up with.  Unfortunately, I am working on a chassis that I have not powered up.  The speaker I have has an open field coil, so could not measure resistance, but I found that the DC resistance should be around 3000 ohms.
  
Adding the total tube current from the data sheet, it comes to 42.15ma, not counting the power dissipation of the field coil.  I used your estimate of 45ma for the calculations.  If this is the total current throughout the B+ loop, I came up with much lower power ratings.  Using the current and resistance values, I calculated the voltage drop across each resistor, then calculated wattage.

The 180 ohm = 8.1 volt = .36 watt.  The 60 ohm = 2.7 volt = .122 watt.  The 3500 ohm = 157.5 volt = 7.1 watt.  Based on my calculations, I should be able to use 2 watt resistors for the 180 ohm and 60 ohm resistors and a 10 watt resistor for the 3500 ohm?  Does that sound reasonable?

The other variable is a resistor to replace the field coil, possibly 3000 ohm at 10 watt?

If my calculations are wrong, please let me know.
Thanks,
johnschw    


Messages In This Thread
Philco 90 WW resistor question - by JohnSchw - 05-22-2022, 11:00 AM
RE: Philco 90 WW resistor question - by JohnSchw - 05-25-2022, 12:48 PM



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