Background:
POTS from CO not off of an IAD or any such electronic device.
Works perfectly at demarc with house wiring removed.
Extended from demarc to 66 block. Works perfectly on both sides of the 66 block.
25 pair cable extends upstairs (100 ft +/-) and is punched down on a patch panel.
All other POTS lines via same facilities work perfectly at patch panel.
The one in question when you go off hook takes 15-20 seconds to return dial tone.
Changing the port and swapping with a known good port (good still good on the "offending" port) gives same results.
Voltage doesn't change from demarc to patch panel

Any thoughts on what I should be looking at next?

Are you 100% positive there is nothing tapped between the 66 block and the patch panel? I would be looking for an alarm panel or some other device that cause a delay in dial tone when initially going off hook.

Rcaman

There are so many ways to shoot a telephone wiring trouble, so here are a few, if not exclusive, suggestions:

I notice that you did not try using a different pair in the 25-pair cable. Use a pair from the yellow group, just as a temporary fix. Pairs in that group, due to the more contrasting colors, are less likely to be punched down incorrectly.

Try inspecting, very carefully, the punch-down of the 25-pair cable at each end, looking for a split or crossed wire. Use a bright light and go at it methodically. There is a one in a million chance that the cable is defective, and a one in 50 chance that you punched down some wire in the wrong place.

When you go off-hook, and there is a delay, it may be that the CO is trying to find the correct Tip for the correct Ring. You may be using the correct Ring with another line's Tip. Some CO equipment will continue to try to provide a dial tone, even if the line is swapped or there is a foreign ground. It may be the cause of the delay.

Once you get the dial tone, does it identify correctly using the CO's ANA feature? Can you call silent battery or establish a call, and if so does it sound clear or is there an unbalanced sound?

Try this: listen to each working line, one at a time, with your test set in "monitor" as you short out the defective line with a screwdriver. Do you hear a click or a crossed dial tone?

Open a all the lines at the source, take a meter and look for a cross between any of the T&R's, testing at the far end (jack).

Open the defective line at the source, and use the meter and see if there is foreign battery or ground at the far end (jack).

Let us know what happens, please.

"Open a all the lines at the source, take a meter and look for a cross between any of the T&R's, testing at the far end (jack)."

Should say:

"Open all the lines at the source, take a meter and look for a cross between any of the T&R's, testing at the far end (jack)."

Friggin' edit feature times out too soon (why do we need it at all?)

Because some users were going back to change a post that was too old, & in doing so, it changed the whole meaning of the post.

Got it.

Look closely at the 66 block, as Arthur said. I've had one in service for a long time that started acting up. Found a tail end of a jumper that didn't quite get cut off when punched down. Worked for a long time that way. Don't know why it worked, and don't know why it started to act up, but it was there.

Jim

I had an odd issue at home after switching to a new cable EMTA - the phone would ring once and then disconnect. I had a loose termination at my 66 block for all the shop cabling. Reterminated and everything works - so check ALL your connections!

Thanks everyone for your tips. Unfortunately on Friday I was pulled for a job my supervisor considered more important and so I wasn't able to look at this until this morning.

I used everyone's suggestions and worked through each in order. When the issue was still unresolved I started over and re-punched connections. Still didn't work. I wasn't going to do anything with the cross connect on the binding posts because the wires were tight and I could see a sliver of copper on both ends. When I did pull them I found one had insulation in the middle--copper both ends.

Thanks again! I love this forum because I learn so much.

So, are you telling us that one side of one cross-connection was open? How would that account for a slow dial tone, rather than no dial tone at all?

I was thinking high joint from the description of insulation under the binding post.

OK, got it.