Ground hum on analog trunks

[Phoneguy15]

I have a site that is running on a G3V6 with anaolg ground start trunks. (I know... old! way old!)

There are several trunks that have hum on the lines.
When I test the trunks on the provider side I don't hear any hum on the line.
I have tried connecting to several different ports on the system but if I connect the trunk to any port, the hum returns.

(Now that I think about it, I have not connected them to a port that is clear and in service on another trunk)

At any rate, I thought I remember reading or hearing that sometimes there can be a problem out in the field (service provider side) that will not be noticeable until it is looped up with the CPE.
Could this be the case and if so, how would I test or prove that it is a problem on the provider side?

I will need to go onsite and try moving one of the trouble trunks to a clear trunk port that is in service now.
That way I can rule out all of the vacant ports being bad.

If anyone has any insight about trouble that's not noticable until looped up with CPE, I would be grateful.

Or maybe I just want to blame the provider needlessly

Thanks in advance,

Todd

 

[mmagen]

Hi, Todd. You have just encountered one of the most difficult problems to diagnose (and fix) in the TDM world. But, let me throw out some ideas for you to consider. You are correct that the Telco can have some bad "coils" in the line that will definitely cause the hum you are experiencing. Good luck getting them to admit it, though. Also, make sure the PBX cabinet(s) is/are all grounded to the same grounding point as the Telco circuits. If not, this can cause a hum, as well. You have the right idea to move an offending trunk to a known good port and see what happens. Also, make sure all of your TN747 are of the same revision (A, B, C) and vintage. Last resort is to replace the ground start trunks with loop start trunks. Unless you have an incredible amount of two-way traffic on them, you shouldn't experience any glare (call collisions), and you can keep the same cards (TN747) just flag the trunk group as loop start instead of ground start on the first page of the trunk group form. Hope this helps. Mike

Mike

Why does the light always have to be at the end of the tunnel?