atcomsystems.ca/forum Forums Wiring - Telecom Carriers - Trunks & Services T1's, CSU's and DSU's 6 t-1's random troubles

I have a customer that has 6 t-1's, all smartjacks are located in the server room. The business is feed by 18pr cable (total cable lenght is 8900ft). The cable pairs have been changed and cable techs have been brought in to check the pairs and naturally they are clear of trouble and bridge taps. The t-1's have been alternating on which one goes into trouble but when they go into trouble the loop light starts blinking and sometimes it goes lights out for 5 or 10 seconds. The t-1 will run errors and if you reset the card it goes back to running clean. By the way the t-1's are single pair adc cards (and the cards have been changed). Any help will be greatly appreciated thank you.

The Transmits & Receives for the 6 T's are all on the same 18 pair cable?

Sam

Ya 'spose it's random lay, Sam? Isn't 18 pair what the 1st 1A2's used?! How old is that cable! John C. (Not Garand)

We have several pretty sharp CO guys that are familiar with this set up. I've never delt with the single pair T-1's.

Woops! I missed that - "single pair ADC's" - so forget the xmit and receive question.

My next question (hopefully better than my last question) is:

Have the circuits been stress tested end to end? Has someone gone out there with a T-Bird or Sunset and run to a hard loop? Or better yet gone head-to-head with a pair of testers, one at each end.

T-1 is just a transport. Let's make sure that the potholes are out of the road before we start checking the suspension.

Sam

hey sam, Yes the t-1's have been stressed with a ameritech and a looping plug in the smartjack. After doing some testing on monday I am beginning to wonder about ac voltage on the cable side, but as for crosses and grounds I can't find anything. Back to the stress test, On monday 1 t-1 crashed in the morning, When I got there the customer had reset the card and it was back to running great. We took the csu off put in a looping plug and it ran for 2 hours before it took 22 crc's. I checked cable pair and it was good then put the remote card back in and it runs great again. Man I am confused. Thank for the replies

Could the AC voltage be building up on the pair and after the remote card gets reset it releases the AC off of the pair. Just a thought, Thanks

I doubt it. AC induction builds on unterminated pairs.

What type of tests did you run? If you haven't done it yet, I would suggest a QRS test. It will pick up physical problems with the span. Another possibility- how about the electrical service feeding the smartjacks? Have you tried a UPS or a Dranetz meter on that?


Sam

How about an upstream mux? Are these 6 circuits connected to a common multiplexer in the central office? Maybe the common mux is causing the problems on all 6 circuits. When you reseat or change the card on a circuit you may just be resetting the error registers in the card and allowing the circuit to come up until the error threshold is reached again.