Don't toss the other power cable out yet.

As someone suggested, clean both the contacts in the connector at the 
end of the cable, as well as those within the fuse blocks, and 
whatever connector or wire you have on the power supply end..

My TS570 went to visit Cliff Holland with that same low output 
problem. He went through it, found nothing out of place, then asked me 
to check the voltage at the business end of my power cable. It was 
11.7 volts, with 13.7 volts on the power supply terminals.

The cleaning job, along with a similar treatment for the power supply 
terminals just in case, fixed the problem.

To clean the fuse holders, I removed the fuses, blasted the holders 
with canned air, then re-inserted the fuses.

Either the air, or the physical movement of the fuses did the trick.

Mike Duke, K5XU
American Council of Blind Radio Amateurs