I was sent to a site where the customer had a beat up cortelco phone, the issue was a extremely loud buzzing sound (not static, with faint dial tone. I replaced the phone lines connecting to the base set; no change. I replaced the base set; still no change. And I replaced the old 1 port jack, with a new one; nada. I decided to isolate the wires from the customers side and then got a semi-clear signal (light buzz) facing the providers demark. When I reconnected the sound came back. I repunched all connections, still; no change. I check the line no open shorts detected (will try another toner next time to make sure). So I am stumped what could be the issue? What did a miss?

Ground Hum. Always check at the Demarc first. Separate customer from telco. Check Telco first, then use a decent meter like a side kick to test the customer side Tip to Ring to Ground. If you happen to know the test number to remove CO battery for a minute or two, use your meter on the Telco side too.

It's not an open, and it's not a short. A toner is not the tool to use to test a line.

Open the line at the demarck. Draw dial tone with a known, good test set or single-line phone that does not require a separate power source to operate. Listen to the line after dialing a digit.

If the line sounds good, proceed to the next step.

With the line open at the demarc AND ALL EQUIPMENT REMOVED FROM THE LINE test with a meter for grounds and crosses.

Put the line back to normal and listen with JUST the test set or common phone at the end location.

You have a ground, a cross, an unbalance, or a defective telephone.

Again, this is why carrying a simple "Sidekick" or similar tester should be part of a normal technician's tools. You could have isolated the problem in one trip in a few minutes. You need not spend a lot of money, these testers are available, used, for very little.

Rcaman

When you replaced the base set did you use the same handset?

Cortelco handsets create a very loud hum when they have gone bad.

Where can I purchased a "sidekick"? Anything beyond a tone tester is basically out of my pocket. I need this job so I will get what I need to do it.

I replaced all of the cortelco parts, no change.

I think it is the line itself, but I do not have wire tester to determined where a break may be.

People I work for are cheap on fixing the issue at hand, so I have to work with what I have.

All you really need for dial tone is a good Butt set to start with. I prefer the Harris Dracon TS 21. Nothing fancy and no battery required. Once you clear the bridge clips or x-connect from your equipment. If the noise is still on the teleco side it is up to them to fix. A sidekick is nice, I usually only need to use mine on private outside plant.

I isolated the connections; on the telco side I get a clear dialtone. When I connected the user (normalizing the connections as they once where) I get the loud buzzing sound again, even when there is no phone plugged into the jack.

I am using a harris buttset.

Does the station cable go directly there? Or are there feed cables? If theretr are feed cables go to the next spot pull the connection and check dialtone back to the Dmarc. You could have a bad house pair or a number of other things to look for.

If you know the trouble is in house a simple volt meter will tell you what the trouble is. As was stated by John, you've identified the trouble as in house, now just chase it down to where.

It is likely that you either have a grounded connector, possible pinched between a duct or water pipe or, in a previous life, there may have been a 10 VAC transformer connected for a Trimline or Princess telephone that is connected to the pair on which you are working.

Rcaman

Until you can determine WHAT TYPE of metallic fault exists, you cannot begin to clear it.

A digital volt-ohm meter costs about ten bucks. And guess what? It's re-usable AND a tax deduction.

Oh such a thing exists? How handy.

My guess in this instance is that there is an imbalance on the line that isn't present at the NID because it is due to a high-resistance open (faulty splice on one side of the cable pair). That additional bit of inside wiring added to the circuit is just enough to bring out the noise. If it's clear at the NID and not after the inside wiring is connected, you're going to have a hell of a time getting the telco to accept responsibility.

Well I managed to find a 2nd cross connect block in a store room. The first two pairs have the same buzzing sound. Again switch to another pair; the third pair was a good clear dial tone. So I got the user back up. Still not sure where the fault is at, but every time it rains some phone wire in this building goes south.

Again guys ty for your advice.

Sounds like an unbalance in the interior wiring. Hopefully it's twisted pair and not quad. If it's quad you'll need to replace it.
Quad is not twisted pair. The other thing that you can look for is bridged taps on that pair (or try another pair or cable).
If it appears to be related to rain, you should replace the cable, really.

Unbalance happens when both conductors aren't the same length electrically (which is usually the same as physically).

Analog phones work just fine on quad wire, as do digital phones. I wouldn't be ripping out quad just because.