Hello just lost a twisted pair. Need help!

[Lw2112]

Hello everyone. I just found this forum. Maybe someone can help me..
I have a 500ft run of cat5e to one of my Hikvision dome cams that's not working..tested and found pair 7-8 are not working. Ive replaced the RJ45s on both ends. Still not working. Can I use another pair in it's place? I only need video.

 

[tangent]

Hello everyone. I just found this forum. Maybe someone can help me..
I have a 500ft run of cat5e to one of my Hikvision dome cams that's not working..tested and found pair 7-8 are not working. Ive replaced the RJ45s on both ends. Still not working. Can I use another pair in it's place? I only need video.

Depends on if the devices use PoE mode A or B. Mode B uses all 8 wires. In standard compliant devices, the PoE switch "decides" which mode to use.
*decides may just be a literal mater of the circuit design.

 

[Q™]

....I have a 500ft run of cat5e to one of my Hikvision dome cams that's not working..tested and found pair 7-8 are not working. Ive replaced the RJ45s on both ends. Still not working. Can I use another pair in it's place? I only need video.

Welcome to IPCT.com @Lw2112. I'm a tad confused, as usual. 1000BASE-T (IEEE 802.3ab) specifies a maximum Cat5E cable length of 328 feet...but you've got a 500 foot run?

 

[tigerwillow1]

Pair 7 and 8 (brown) are used only with mode B POE, so you could change over to a switch that uses POE mode A. If you're using a power inserter, it likely uses mode B and you need lines 7 and 8. It's my understanding that with mode B, the brown and brn/wht wires are used in parallel. Did you lose both of them? That would be a weird random event. Maybe a rodent snack attack?

 

[tangent]

As Q™ noted you are over the spec'd max distance. Some cameras, switches, and cables will handle that better than others but there's more potential for issues. For example dahua has their ePoE line of cameras and NVRs. Some switches have an 'extend' mode that limits the switch to 10base-t and does a few other things to improve long distance support.

 

[Lw2112]

Thanks for your replies.. actual distance is approximately 350'. This cam worked fine for about 3 months so distance is not the issue. The line is exposed and runs along conduit for approximately 200", 12' up, down a walkway to a garage. My tester tests pairs..My guess, a bird landed on it . If I could use a different pair, which one would you think would be the the best.? I'm just want to avoid replacing the whole line..its a shot in the dark but worth it.

My next thought is to use a tone generator and trace the whole run and splice.

 

[mat200]

Thanks for your replies.. actual distance is approximately 350'. This cam worked fine for about 3 months so distance is not the issue. The line is exposed and runs along conduit for approximately 200", 12' up, down a walkway to a garage. My tester tests pairs..My guess, a bird landed on it . If I could use a different pair, which one would you think would be the the best.? I'm just want to avoid replacing the whole line..its a shot in the dark but worth it.

My next thought is to use a tone generator and trace the whole run and splice.

Hi @Lw2112

Looking forward to finding out the root cause on this one.

Solid copper wires?

I would also re-check the end points - sometimes a poor crimp job results in a similar failure over time.

Visual and tone generator inspection should be useful.

 

[tigerwillow1]

I'll try explaining differently.
Mode A POE uses 2 pairs. 7-8 (brown) is not one of them.
Mode B POE uses all 4 pairs.
Therefore, if losing 7-8 causes a failure, you must be using mode B. There is no different pair to use, because all of them are required.

As mat200 was inferring, I'd spend more time confirming the diagnosis. If a conductor broke in the middle of the run, there must be some physical damage, and you'd need to know if it was some sort of one-time freak occurrence or not. Otherwise, it could be likely to happen again.