I picked up a used Katsumi Elekey EK-150 (manual) electronic keyer.
I'm trying to get it working with my Kenwood TS-570S (manual), which has a 3.5mm Key jack. With a male-male audio cable connected to the Key jack, if I short the positive and negative leads together, the transceiver transmits CW, as expected. The paddles on the keyer also produce tones through they keyer's own monitor speaker, as expected.
However, I can't figure out how to get this keyer to interface with the radio properly. Regardless of the keyer mode (Relay / Tr. Switch) When I connect the keyer's Keyed Line output to the transceiver's Key jack, positive to positive (tip), negative to negative (sleeve), operating the paddle does not cause the transceiver to transmit. If I reverse the polarity, positive to sleeve, negative to top, the transceiver constantly transmits, regardless of paddle operation.
What would you expect a multimeter to be able to detect on the keyer's Keyed Line output? I detect a voltage of a fraction of a volt between the positive and negative leads, but neither the voltage, resistance, current, nor continuity between those leads changes when I'm keying vs when I'm not. I don't know exactly what is expected, but that seems strange to me. Is this thing broken?