In January, I was invited to consult on a continuing DSL High Speed Internet (HSI) outage on the West Coast. It was one of those crazy “Is it a power problem?” or “Is it a cable problem?” scenarios with lots of finger pointing. Meanwhile, the customers were up in arms.

The Complaint
About 7 months ago, the repair department started getting calls from one area complaining of an ADSL service interruption starting around 6:30 A.M. and continuing until around 9:00 P.M. Monday through Friday with no problems on the weekend. The biggest complaints were modem dropping and modem retraining repeatedly.

There were a total of 15 customers in a 25-pair cable that was about 18,000 feet from a #5 ESS central office. These customers were in service for more than 10 years with few prior problems.

The Technician
Eventually, the problem was turned over to Rick, a senior cable maintenance technician with 32 years of field experience. Rick had several pieces of test gear to test the physical layer, the DSLAMs, and the modems.

Safety
Rick first noticed a distribution power transformer that was emitting an audible hum that could be heard at ground level. Being super cautious, he used his voltage tester and it showed +200VAC.

Rick contacted his supervisor who, in turn, contacted the Telco power engineers and the power company. Without taking one test set out of their vehicles, the engineers and the power company determined that the voltage was induced.

I encouraged Rick and his supervisor to get the power company and the Telco power engineers back to eliminate the safety hazard before proceeding any further on the bandwidth problem.

The power company changed out the telephone pole and the transformer. The Telco power engineers set up grounding parameters and when they were met, the safety problem was solved.

The Physical Layer
These customers were getting 2 services over the copper infrastructure: POTS and HSI. I wanted to confirm that we had quality POTS service before proceeding to the bandwidth problems.

I had Rick test the vacant cable pairs to make sure that they were clean with good longitudinal balance. When they passed, we did active line tests for Loop Current, which averaged 29 to 31 Ma, acceptable Network Interface ground which averaged 0 to 25 ohms, Circuit Loss averaged 7.5dBm, Circuit Noise was around 2dBrnC, and Power Influence averaged 43dBrnC. AC voltages tip and ring to ground averaged around. 2VAC, and all pairs showed a longitudinal balance .70dB.

Chasing the Wrong Dog
After eliminating the physical layer as route cause, Rick then looked at the DSL. When the services were working properly after sync, downstream showed 3.2 Meg with a margin of 26dB, and upstream showed 1 Meg with a margin of 23dB. When failing, max downstream speed was 238k with a margin of 5.5dB.

The next step we took was to look for interferers, however, nothing obvious showed up on the spectrum analyzer. A visual drive of the route showed ham radio antennas; Rick approached the ham radio club and their transmitting did not coincide with the HSI failures.

Rick then checked with the water company and found that they used radio to indicate when the water tank was full, but that also had no effect on the HSI failures.

The Root Cause (Dirty Power in the Residence)
After reading my forum on my website at www.mccartyinc.com and some advice from an old Contel friend, Rick started driving around the neighborhood with his AM radio in the truck tuned to 530 (no AM station there), and he would get a hit on the radio; however, he could not pin it down. Rick then went to Radio Shack and purchased a portable AM radio and walked around the area.

He then took his Dynatel 573A cable locator receiver set to RF, and it vectored him to the house that was the root cause of the trouble. Rick had the homeowner turn off the power to the residence and the problem went away. The instant power was restored to the residence the trouble returned.

The following Monday, Rick was dispatched again; and this time he had the homeowner shut down one circuit breaker at a time. The problem was in the guest bedroom and part of the master bedroom. When the TV was unplugged, the problem went away.

The problem occurred only when the TV was turned off. When the TV was on, the DSL problems went away. Keep in mind that when this particular model of TV was turned off, it was not completely off but was in standby mode -- and that’s when the 15 customers in the neighborhood had a problem.

Rather than having to return, Rick went to the store and bought the customer a new TV and took the old one with him. Rick said buying the new TV was the only way he wouldn’t have to go back to this rather remote location. Now that’s what I call technician persistence and ingenuity -- and that is what service is all about.

An after note: Rick is getting a lot of Thank You’s from satisfied customers. Good job!

Signing off
Please call me or email describing when your ingenuity and persistence paid off and even if it didn’t. Maybe the readers and I can help. If you have one of those tough cases, tell your boss to call me and I will consult on a case by case basis. To contact me, send me an email at dmccarty@mccartyinc.com or call me at 831.818.3930.