Al Ludwick / NN4ZZ
Here are 2 things to look at. Easiest first......
1 - check the power cables between the power supply and RF deck. They can pull out due to the weight and cause errors. Re-seat the cables to insure a good connection.
2 - measure the voltage coming from the power supply, it should be around 72V. The pinout is in the power supply manual on page 17. (if you don't have the manual, I can post a snapshot of the page). This may give some clue as to whether the voltage is really off and whether problem is in the power supply or metering in the RF deck. For reference mine measured 74.5 V last time I checked.
Hope it helps and good luck with FT4TA
Regards, Al / NN4ZZ
al (at) nn4zz (dot) com