3300 CXi ONS cards keep failing

[bigdave1980]

We have a customer with a Mitel 3300 CXi, with a single ASU containing a pair of 16 port ONS cards. Yesterday I attended their premises and replaced a failed ONS card for the 2nd time this year. I have been told by colleagues that it is very unusual for one of these cards to fail.

I do not know a huge amount about the Mitel hardware, but my theory is there's a fault somewhere within the end user's cabling, such as a short, which may be damaging the cards. The fault presents as a clicking noise on some ports, other ports going into a locked out status, and others just being totally dead.

Upon inspecting the faulty cards, I can see that one or more of the components on each has been damaged by heat. I will add a picture with an example of this circled. The component, whatever it is, turns a very dark colour.

Has anybody else seen this before? Does my theory of a short somewhere, possibly causing to much power to be drawn through one of the ports or causing a port to be over-volted sound plausible? May it be a faulty ASU even? I don't think it will be long before I have to go back there again to replace another of these cards.

Any suggestions would be very much appreciated, please.

Thanks!

 

[Billz66]

whats the environment like where the asu is installed ?
is it clean and cool ?



we have approx 15 ASU's still in the field - cant remember us ever having issues with any cards
from memory ours are all 24 port so they may not be as old as yours
Whats the age of the cards ?

If I never did anything I'd never done before , I'd never do anything.....

 

[jpruder]

I would think this would happen most often on an unprotected feed off premisis

 

[AlphaMann]

We had one customer with a system that they had in the same area as their vacuum system.
They did cabinets and they burned through cards until we moved the unit to an upstairs office away from it.

Other possibility could be a short on one of the lines connected to that card?

 

[bigdave1980]

Thanks for your replies.

@Billz66 It's rack mounted in a small cabinet under a desk in an office. It was slightly warm in there last time I visited the site, and it's not massively dusty in there. I don't think it's warm enough to be causing the cards to burn out.
@jpruder Their ONS card is only connected to analogue extensions within the premises, there are no external analogue circuits connected to the Mitel.
@AlphaMann Yes I am almost convinced that there is a short somewhere in the customer's cabling within the building which is causing the cards to burn out. I have witnessed first hand that there are rodents on site and that they have been chewing telephone cables. We do not have responsibility for their internal wiring under their maintenance agreement with ourselves, so they use a 3rd party electrician for that. I can't really do any proper fault-finding on their cabling therefore, but it's costing us money as we are repeatedly replacing the ONS cards under the maintenance agreement when they burn out. Whatever it is also also killed my test butt set last time I was there.

I think I can probably pinpoint which extension/s are causing the problem. I wonder if there's some way I can test each pair from the frame where the Mitel connects to their internal cabling to prove where the short is, though?

 

[Billz66]

what about some form of surge protection

https://www.apc.com/au/en/product/P...r-for-analog-dsl-phone-lines-2-lines-4-wires/

https://kingsmillindustries.com/product/krone-lsa-plus-telephone-signal-protection/

also is it an asu or an asuII.
looks like ons cards for ASU II include surge protection. havent found any old docs yet regarding asu

If I never did anything I'd never done before , I'd never do anything.....

 

[kwbMitel]

One thing that can cause premature failure is Message Waiting Lamps.

This has been true for all generations of Mitel hardware right back to the SX200 Analog

If the phones don't require lamps, Make sure the ONS Descriptor has it disabled.