Got some unexpected time today to look at the rotor. First I set the output at pin 6 of the external control output jack to 5.0 V. Then I got readings every 45 deg from 180 at the left to 180 on the right. The readings are of course subject to parallax in reading the needle. Readings from 180 on the left to 180 on the right were 0.024, 0.606, 1.270, 1.864, 2.489, 3.074, 3.690, 4.350, and 5.000 V. The difference in voltage from reading to reading varied from 0.582 to 0.660 V. From left to right they were 0.582, 0.664, 0.594, 0.625, 0.585, 0.616, 0.660, 0.650. I then took resistance readings on the 500 ohm pot in the rotor (removing connection from control box each time). Starting at the left resistance from 1-2, 1-3, 2-3 were 415, 416, and 1.7 ohms. With the rotor halfway around (360) (dial reading 345) resistance from 1-2, 1-3, 2-3 were 241.7, 416, and 176.1 ohms. With the dial at 360 resistance from 1-2, 1-3, 2-3 were 220.4, 413, and 193.6 ohms. With the dial at the right 180 resistance from 1-2, 1-3, 2-3 were 30.4, 414, and 383 ohms. First observation is that the pot in the rotor is considerably less than 500 ohms. Next with either the rotor being halfway around or the dial reading as if it were halfway around I would expect the 1-2 and 2-3 readings of the pot to be somewhat similar but they are not. So, are these results glaringly pointing to the 500 ohm pot as the culprit? Or does someone see something else?
I’d appreciate any opinions on this. Thank you once again.
73 Al W8KHP