The course of action for fault locating the Triple Play service requires a step-by-step procedure starting by qualifying the Plain Old Telephone Service (POTS) first. Fixing problems with the POTS service will usually restore the bandwidth services.

Most field technicians are responsible for the cable shield, the cable pair including the inside station wire, associated jacks, base cords, and end user equipment, such as modems and set-top boxes. Likewise, originating equipment for POTS, DSLAMs, and video input equipment for IPTV is the responsibility of central office (CO) technicians.

When a customer problem is dispatched to the field, the best place to start troubleshooting is at the remote. The field technician can remove battery and ground from the POTS portion of the service by pulling the module at the remote or disconnecting the distribution plant at the cross-connect at the remote.

Any good multi-functional test set can glean good information from the vacant cable pair. Keep in mind that some faults will only affect one of the services and some faults will affect all services.
Following is my process for testing:

Step 1. Test for AC voltage tip- or ring-to-ground.
If a hazardous AC voltage is present, most multi-functional digital multi-meters internally disconnect from the circuit and display the type and value of the voltage either AC or DC. Lower voltages greater than 50VAC are hazardous, and the source should be identified and rectified.

Step 2. Test for longitudinal balance.
Longitudinal balance should be greater than 60dB. Some test sets show longitudinal balance and others indicate stress test. The stress test should show less than 30dB when calculation shows longitudinal balance greater than 60dB.

Step 3. Test for unwanted DC voltage tip- or ring-to-ground.
Acceptable voltage would be 0VDC. High resistance paths to crossed battery from other circuits indicate less battery on a VOM. For example, testing a vacant conductor crossed with -51VDC through 270,000 ohms would indicate around -22VDC on most high impedance voltmeters.

Step 4. Use the ohmmeter function to test for any short or ground on the circuit.
The pair should test clear greater than 30 Megohms. Faults lower than 30 Megohms may not affect the POTS portion but will affect the IPTV when the fault is ionized by ringing voltage. Usual customer complaints indicate that the set-top box drops when someone calls.

Next, measure the distance tip- and ring-to-ground with an open meter. The pair should be capacitively balanced. For example if the ring-to-ground open meter measures 3,000 feet, the tip conductor-to-ground should also measure 3,000 feet. If there is any difference, divide the small number by the large number. This will give you the percentage of capacitive balance. For DSL and IPTV the capacitive balance should be greater than 98%.

Now take note of the tip-to-ring measurement on any balanced cable pair; the measurement should be a bit longer than tip- and ring-to-ground. If the measurement is less, suspect a split cable pair. This can be confirmed by placing identification tone on that pair. If the pair is split with another pair there will be less tone on other pairs and an equal amount of tone on the pair that your circuit is split with.

Step 5. Place a grounded short at the remote and go to the customer’s network interface.
First, visually inspect the network interface to make sure that it is grounded to the power ground electrode at the residence.

Remove the inside station wire and do a longitudinal balance test back to the grounded short at the remote. The longitudinal balance should show greater than 60dB. Any measurement less than 60dB would indicate series resistance on the circuit.

Select ohms on the VOM and measure ohms tip-to-ring, then tip-to-ground, and then ring-to-ground. On a balanced circuit tip- and ring-to-ground should be the same value and one-half (1/2) of the tip-to-ring measurement. Any difference in measurement greater than 5 ohms between the tip and ring will affect the longitudinal balance and will decrease bandwidth on the DSL and IPTV service.

If tip-and-ring measurements show more than 25 ohms greater than one-half of tip-to-ring ohms, the telephone ground and the power ground electrode are not of the same potential. Remake or replace the network interface ground.

Step 6. A visual inspection of the network interface is in order.
Then test the inside station wire for any crossed battery from a second service or any short or ground on the inside station wire. If a shorted cable pair from 1.5 Megohms to 3 Megohms is identified, remove the end user equipment (i.e., telephones, printers, fax machines, etc.) and retest. After the end user equipment is removed the inside station wire should test clear greater than 30 Megohms.

This step-by-step process identifies faults that affect all aspects of the Triple Play service. Then, and only then, sync up to the DSLAM with your test set or testing the bandwidth portion of the service.

Signing off
I have a great opportunity for you: call me or email me with your toughest case of trouble, and I bet I can help solve it and then write about it (I won’t mention your name, location, or company if that’s your preference). That’s some serious free consulting time for you and I’m looking forward to a challenge! Contact me at 831.818.3930 or dmccarty@mccartyinc.com. And check out my blog on OSP® magazine online: www.ospmag.com/columnists/mccarty/talkback.

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