Currently, DC power for amplifiers ZHL-1000LN+ is supplied by Aligent E3620A.
I tried to use power supply from the side of 1X1 rack, but fuse plug(Phoenix Contact ST-SI-UK-4) showed red LED, so I couldn't use it.
We fixed things so that we are now using regular fused rack power for these amplifiers. The fuse no longer had a red LED, but it measured open when we checked the resistance. Although, somehow (magic?) 13.73V were getting to the other side of the fuse.
Anyhow, replacing the fuse with a new one fixed the problem right up.