Cannot break dialtone

[telcoengineer]

We have an Office 250 HX V6.3 that occasionally cannot break dialtone. Once the system is reset it works fine for a few days. Comcast is the service provider, we have verified polarity is correct.  All four lines in the controller and two on the LSM are affected. We've ran Hybrid Balance and Loop Loss tests but it keeps happening.

[DND ON]

Did you measure voltage and loop current on the lines to make sure they're within normal range?

[telcoengineer]

It was not measured with any DVOM, the tech out there has a Loop Current Tester from sandman.com that has always served him well, everything was green on the tester.

[acejavelin]

Honestly, this sounds like a bad processor... one or more of the DSP or DTMF generators are failing, we have had it happen before. If you work with support they can help you narrow down the cause but really you just need to RMA the processor or replace it.

[telcoengineer]

We went onsite today and measured the on hook is 1vdc and off hook is 17vdc with a butt set and 7.86vdc with going off hook with the Mitel

That doesn't seem right to me.

[DND ON]

The Sandman website has some great tips on troubleshooting, along with a chart showing normal voltage/current ranges.

I once had an argument with AT&T because a phone line worked with the technician's butt set, but not in the PBX. After I showed him my test measurements, he somehow found a bad pair at the cross box.

[telcoengineer]

after resetting the comcast boxes the on hook voltage went up to 50vdc. that seems right. we will.play the waiting game to see if it happens again and measure voltage if it does. 

Sent from my SM-G955U using Tapatalk

[acejavelin]

To be honest, voltage is a far less concern than loop current... as long as it's under ~55vDC, we have connected LS ports to ATA's with voltage around 20vDC and not had any issues. And the 5000 doesn't like loop current much under 22ma or much over 30ma.

[Teck900]

We have had this same problem with multiple 250 lately and now with an SMB. all on comcast.  have you found a fix for the problem besides replacing the processor board ?