sundance-communications.com/forum Forums Other TDM Phone Systems 1A2 and Comkey Telephones & Systems 1A2 shoebox probable short

Hi, I have a WECo 551B shoebox KSU with three 400D cards and a 401 ICM card, which has been working perfectly for several years. The incoming CO line 1 goes on hold when the switchhook is depressed on the telset. I figured there was a short in the 400D card, but I've rotated lines 2 and 3 cards through the 1 card position, and that has no effect. I can't find any obvious shorted wiring. When the CO line is completely disconnected from the KSU, it give a good dialtone and in- and outbound calling through a butt set; however, when punched back to the connecting block, the hold situation occurs once again. Calling that line gives a busy signal. Does anyone have a suggestion on what's causing this action or a place to start checking this? Thanks, Bill

You may have a bad switch-hook on one of your multi line keysets.

Start unplugging one at a time and see if one resolves the problem.

Good luck and take care of the ole Girl.

A 400 card puts the call on hold when it sees Dial Tone on Tip & Ring and no ground on the A lead.

Check to see if you have ground on your A1. Short the A & A1 together and the line should come off hold. If it does continue troubleshooting each set from there.

Sam

The mystery is partially solved.

I replaced the 2563 key set with headset jack with a regular 2565, and everything was back to normal. I now need to see why the 2563 is acting up. First place to look is at the 'rigged' caller ID box lead on the 1T/1R terminals! It's always something!

Thanks to all who responded.

Bill

The caller id box may have a high enough short to cause this. "a short on the tip and ring when the A lead goes open will cause the line to hold"

Update: the 2563 keyset checked out okay as did the shoebox KSU, so I checked the callerID box, and it was the culprit. I should have known the 45-year-old WECo stuff would keep operating as designed and the 21st century callerID box wouldn't!

Is the CID box located at the telset location?

Is it wired so that its T&R are connected across the T&R of a CO line, inside the set? If so, that's not the right way to do it.

You need to take a spare pair in the connecting cable and mounting cord, (yellow-blue, yellow orange, or yellow-green) and send the CO T&R to the phone over that pair, making sure that at the KSU end, you derive the T&R *BEFORE* the line card.

Since a 400-type card (and indeed relay-based 1A1 line circuits before them) place a call on HOLD by first opening the A/A1 ground, followed by opening the T&R, any high-resistant short across the T&R (as we suspect is happening inside your CID box) will cause a false HOLD condition.

This used to plague repairman, in cases where the installers would either be too lazy or too stupid to install CMB, when too many line ringers inside telsets would be installed in a large office. The total capacitance of all the ringers would cause the line to go on false HOLD.

Yes, the CID is located at the telset.

So, Art, you're saying to take a spare pair and terminate it on terminals 43C and 44C of the block inside the KSU and the connect the CID box to the same pair inside the telset? That would of course bypass the 400-type card.

I'll do that. The CID box is currently on 1T/1R inside the set, and I can see now that the 400-type card is between the CO T&R and the telset 1T&1R.

Bill

Correct. Cut down the spare pair in parallel with the incoming CO T & R in the KSU and then connect the CID box to the same pair inside the set.

However, in the long run, there must be something wrong with the CID box to have caused this problem in the first place. Can you put an ohmmeter across the two input leads of the CID box and tell us if you see a resistance? You should see just a small kick, at first, then an open circuit.

An ohm check on the CID box found that there was a short inside, which revealed itself originally through the false hold caused secondarily by improper installation of the CID box across the 1T/1R leads inside the 2563 telset as described above.

I actually have two CID boxes in this installation, so I terminated the Y-Bl pair on 43C/44C terminals and terminated the Y-G pair on 45C/46C of the KSU. After finding the insulated and stored y-Bl/Y-G pairs buried completely under the 636A key in the most inaccessible possible location in the telset(and then putting all that stuff back together), I connected the respective pairs to new CID boxes. Everything works perfectly now. Thanks to all who responded, and especially to Professor Bloom.