My trusty Kenwood TS-590 is giving me fits - getting full 100W output on 6 meters but only ~60W on all HF bands. Power supply shows steady 13.8V on the meter, but I suspect voltage drop under TX load. Has anyone else encountered this classic TS-590 power feed problem? I'm measuring 13.68V at the rig during 40m transmit, which seems marginal for the finals. Planning to check fuse holders and power pole connectors next, but wondering if there are other common culprits in the DC feed path.

Classic TS-590 issue - the 25amp fuse holders and other connectors on the power cable oxidize over time and can cause significant power loss, causing the rig to reduce power output. Remove power cable, inspect, wipe all connectors clean, pull out and clean fuse contacts, or simply reseat the fuses - also inspect Johnson power pole connectors.

Had the exact same symptoms on my TS-590S! My original power cable was a mess - crappy fuse holders and connectors resulted in a 2.4V drop at 100W, bringing supply voltage down to 11.4V and causing massive power drop-off. Made a new cable with 10mm² wire and no fuse holders - problem solved.

Voltage drop under TX load from poor power cables, corroded fuse holders, or loose connections - the rig needs ~13.8V at the finals and even a 1-2V drop limits HF output (6m often draws less current). Measure voltage at the rig's DC jack during full-power TX into dummy load - that'll tell you if it's the feed or internal to the rig.