04-30-2017, 10:56 AM
It seems this discussion is going around in circles.
The real question is whether the radio is drawing excessive B+ current from the power supply. It is very easy to measure. Just connect your DC voltmeter across R100, indicated on your photo. This is the wirewound bias resistor and the full B+ supply current flows through it. The current here is pure DC, so there are no complicated waveforms to worry about. Measure the DC voltage across this resistor, then divide the voltage you read by the resistance of R100. You can measure the actual resistance of R100 if you want to be very accurate. The voltage divided by the resistance will give the current draw in amps. Multiply by 1000 to get mA.
If this current is close to 0.1 Amp or 100 ma, then the radio circuits are fine and there is no excessive current drain.
If the current is ok, then the 300 ohm series resistor is getting as hot as it is supposed to. Remember, wirewound power resistors are designed to operate at very high temperatures (several hundred degrees) at their rated power dissipation. If you want a cooler running resistor, derate it ( use a higher power rating resistor) or use one which can be heat sinked to the chassis.
The real question is whether the radio is drawing excessive B+ current from the power supply. It is very easy to measure. Just connect your DC voltmeter across R100, indicated on your photo. This is the wirewound bias resistor and the full B+ supply current flows through it. The current here is pure DC, so there are no complicated waveforms to worry about. Measure the DC voltage across this resistor, then divide the voltage you read by the resistance of R100. You can measure the actual resistance of R100 if you want to be very accurate. The voltage divided by the resistance will give the current draw in amps. Multiply by 1000 to get mA.
If this current is close to 0.1 Amp or 100 ma, then the radio circuits are fine and there is no excessive current drain.
If the current is ok, then the 300 ohm series resistor is getting as hot as it is supposed to. Remember, wirewound power resistors are designed to operate at very high temperatures (several hundred degrees) at their rated power dissipation. If you want a cooler running resistor, derate it ( use a higher power rating resistor) or use one which can be heat sinked to the chassis.
