DLT's LEDs Flashing

I have three DLT's and all have the same symptoms - when a button is pushed it blinks the blue LED and nothing else happens. It will allow you to access the next page but still the same result for the buttons.
It has started working again after a while in the past (this is not the first time this has happened) but I need to fix it. This time I was able to check voltages, disconnect wires and generally try and find out what was happening.
It appears that all 3 are faulty! There is 30.5vDC at the DLT terminals.
I replaced two DLT's with 4 gang CBUS switches to allow a bit of light tonight. The other DLT was replaced with a new DLT (date 2010) and is operating OK.
I have two older power supplies and a new DIN rail mounted unit powering the system.
I have searched the Forum for DLT faults but it looks like they are pretty reliable.
Why did I have 3 fail?
I have another two new DIN rail power supplies to install to replace the older units.
Any ideas?

 

There are faults on the network.
I have four old voltage free 4 channel modules that appear in the database Unit Type column summary as ERROR in red but still work OK. The message I am getting is that I need to remove a burden but I do not have any enabled or hardware ones plugged in.
There are about 70 units on the house network that is faulty. The garage has about 20 units and is connected via a bridge. The garage network is OK.

 

Are the powersupplies the old white/cream type units, 5100PS? If so thats what my bet would be on..

 

Yes they are. I dragged the crow out to check the CBUS wave form but I need to figure out how to use it again.
Looks like a power supply change coming up!

 

Feedback for the DLT designers - no one noticed I had replaced two of the DLT's with 4 gang switches. All they did is just turn the light on. So much for technology.

 

Wouldnt bother with the CRO..haha.. Just replace the powersupplies and should be back up an firing..

Not sure I get this comment.. Unsure of why it would be up to the DLT designers to notice you have replaced 2 Dlts with 4G switches?

 

I replaced the old power supplies. There were three of the 5100PS type. I had a new one of this type but decided to use 3 of the DIN rail mounted 'new' type 5500PS.
This fixed the problem.
I reinstalled the three DLT's that had the flashing LEDs and they worked!
There are two 5100PS power supplies for the network in the garage. I guess they should be replaced at some stage.

Thanks for your help Roosta.