Procurve 1905 strange POE behaviour

[hudson0804]

We are having a problem with the HP 24 port POE switches in that they don’t always supply power. I think that we have isolated it to the following:

1. Plug a poe device in first to say port 1 and the unit will power up.
2. Plug a PC into port 13 and the poe device will continue to work.
3. Unplug the poe device and then plug it back into the port 1 and it won’t work.
4. The same happens if you reverse the ports so that the poe device goes into 13 and the pc into 1.
5. It follows this pattern along the switch ie if a pc is already plugged in then the poe device won’t work when plugged into its opposite number.
6. This happens when there is only one pair of devices plugged into a switch.

Any thoughts?