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Transformer burn-out over Cat 5 STP?

Transformer burn-out over Cat 5 STP?

Transformer burn-out over Cat 5 STP?

Has anyone ever seen or heard of a problem with Cat 5 STP (or UTP) actually causing low voltage transformers to overheat and burn out?

Part of the network at my company is a shop floor data collection system. Cat5 STP runs from machinery workstations in the plant to patch panel/punch down block in our wiring closet. Cat 5 UTP patch cables run from patch panel to daisy chained 6-port receiving units (the master receiving unit feeds shop floor data to a server via a null modem cable). The 6-port receiving units are powered by Class 2 transformers (Output: 12VDC 1Amp / Input: 120VAC 60Hz 16W). Since we brought the shop floor system up live on Dec. 1st, we have fried 8 transformers and our shop floor system is now down (no more back-up transformers...we have more on order, but no point in plugging in until I figure out what's causing the burnout.). The circuits in the wiring closet check out okay. The transformers were plugged into surge protectors and the protectors check out okay. At not time did the overheating transformers trip any breakers or surger protectors. The manufacturer of the transformers said that it's possible that there is a crossed or shorted Cat 5 cable that could cause the transformers to heat up and burn out. The cable runs were installed by a company that has since gone out of business (maybe this is why?!) so I have no one to call. I will be checking the cable runs with a modular cable tester, but thought I'd post here to see if anyone can enlighten me as to what the hell is going on or what I should be looking for. Thanks, Steve G.

RE: Transformer burn-out over Cat 5 STP?

Just in case anyone should run into this, I traced problem...using a mod cable tester, found one cable run with a tip/ring reversal (anyone care to explain what this means?) according to tester booklet. Anomaly was red LED on test unit receiver for reversed pair. This cable was transmitting data, but along with that was enough current going back the wrong way to fry the transformers. I've disconnected that cable run and will repunch the ends and test again at a later date. Since I went around the bad cable run, our system has been up, all transformers within acceptable temp range and running fine. Thanks.

Steve Gubin

Smurfit Press
Systems Manager

RE: Transformer burn-out over Cat 5 STP?

Testers are built to conform to telephone terminology. Like it sounds, the "tip" line is used to signal that the phone is off-hook, and the "ring" line is what the ring voltage is sent down. It's just a different way to label the wires. In networking you you label them (+) & (-), for phones they are labeled "tip" & "ring". What your tester is telling you is simply that the (+) & (-) wires were reversed on one of you pairs.


RE: Transformer burn-out over Cat 5 STP?


Thanks for the info, I appreciate it.

Steve Gubin

Smurfit Press
Systems Manager

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