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Things I hate doing: ethernet RJ45/8P8C plug replacement

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  • Chuck(G)
    replied
    I've always kept a "chain" of 8P8C crossover adapters around. I don't have much use for them nowadays, but back in the early 10BaseT days, they were pretty useful. Basically a plug and socket in same housing, much like the serial port DTE/DCE adapters. Neither was very expensive and beat the heck out of making up a special cable.

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by GiGaBiTe View Post
    Adding a third would always take the network down the moment it was plugged in because the required crossover cable to use a normal port for the last hub wasn't available. The computer repair teacher was an old retired I think airforce guy and his knowledge in some areas (specifically networking) was very limited. We gave up trying to get him to buy the right equipment and just abandoned the third island table. It wasn't used that much by us anyway, but some of the later classes were always annoyed.
    Yeah, he should have known a crossover cable is easy to build by wiring 568A on one side and 568B on the other.

    Local high schools had the same problem, hiring people to teach "computer" classes that were not qualified. Often times, for some reason, mathematics teachers were tasked with this. The high school I taught at was technical only, what used to be called "vocational" but geared toward IT and related. CCNA classes, Comptia A+ classes, Robotics and CNC (A/B. Fanuc, etc..), CAD/CAM (Mastercam, Solidworks, AutoCAD, ect..), Medical Information Technology, ASE Automotive Tech, etc..

    Those poor repurposed mathematics teachers would show up at many of the same IT conferences I was at. They were so lost and confused, I felt so sorry for them. During a CCAI class final test for recertification I was in some of them broke down crying.

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by Chuck(G) View Post
    I saw some rare and expensive equipment fall to the bolt cutters and sledgehammers around 1975, including two last STAR-1B systems. I smuggled out a Bryant 4000 platter with the idea of making a coffee table out of it, but ditched it in a move.
    Big enough to make a coffee table! That would have been awesome, I wish you would have built that. The biggest aluminum platter I ever got my hands on was around 16" in size. I have no idea what drive it came from but I thought that was huge, LOL. I ended up turning that into a clock that hung in the classroom for a while.

    Leave a comment:


  • GiGaBiTe
    replied
    Originally posted by kc8eyt View Post

    10baseT is good for 100M (338ft) lengths, must have been a huge classroom! I wonder why you're teacher was running into issues. The setup was within the Ethernet 5-4-3 rule. Some hubs have a dedicated uplink port that needed to be configured either through the use of dip switch or through software. Perhaps that is the issue he/she was running into?
    The shop room was big, but it wasn't that big. The reason we needed three switches is because equipment on the island tables in the middle of the shop was always being swapped around and multiple ports were needed. Linking three switches together was cheaper than having to make up a bunch of patch panels and having to shuffle wires around constantly.

    The hubs he kept buying only had one uplink port, for a maximum of two hubs. Adding a third would always take the network down the moment it was plugged in because the required crossover cable to use a normal port for the last hub wasn't available. The computer repair teacher was an old retired I think airforce guy and his knowledge in some areas (specifically networking) was very limited. We gave up trying to get him to buy the right equipment and just abandoned the third island table. It wasn't used that much by us anyway, but some of the later classes were always annoyed.

    Leave a comment:


  • Chuck(G)
    replied
    Heck, CDC was doing this with their 6+ foot tall 808 hard drives in the 70s. The dictat from on high was that "no piece of decommissioned equipment shall leave the premises in salvageable condition. This was after some customer assembled a complete system out of surplussed parts and took out a service contract on it. Bill Norris reportedly went through the roof when word of this reached him.

    I saw some rare and expensive equipment fall to the bolt cutters and sledgehammers around 1975, including two last STAR-1B systems. I smuggled out a Bryant 4000 platter with the idea of making a coffee table out of it, but ditched it in a move.

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by Chuck(G) View Post

    You have to wonder if pulling out all that coax and replacing it with 4 twisted-pair unshielded cable was really necessary. After all, 2wIP used in industrial applications can handle 150 Mbps over 600 meters--and can even include PoE. 2wIP isn't fussy about cables. Single twisted-pair or coax are just fine.
    The stuff I was replacing was generally RG58 in small to medium sized businesses. When I was in the Marine Corps I believe they used thicknet between the hangars, RG6 I think but it might have been even beefier than that. The hangar complex at Cherry Point was huge so that signal traveled far. Back then IT was handled by a civilian unit (Whizmo they called it if I remember correctly) so I never got a chance to play with it first hand.

    A crazy story: Since I worked on the electronic warfare systems of jets I always carried at minimum a final secret clearance. One day the information officer needed a second signing set of eyes to open a secure safe and remove hard drives from it. Since I had the clearance I was ordered to help. We took the hard drives down to Whizmo TO BE DESTROYED! This was 1987 and hard drives were expensive. I watched in horror while a big machine chewed those drives to shreds. These drives had to be replaced every so often and then the old ones destroyed for security reasons. It wasn't until 1989 until I could afford my first hard drive, a 10MB used full height. I'll never forget that. LOL, it was shocking.

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by GiGaBiTe View Post

    Sounds like dielectric grease. I use that stuff in RJ45 connectors in harsh environments, it keeps the connector from corroding by keeping moisture out. It's especially important to use it in PoE applications, 24/48v causes things to corrode to hell real quick.



    Yeah, switches were generally in the hundreds of dollars range when you could get a hub for like $50.

    I remember back in high school computer repair class we were trying to build up a 10/100 ethernet network and needed three switches to span the length of the shop (it was a very long room.) The teacher kept buying hubs despite us telling him we needed switches. Connect more than two hubs together and the whole network goes down. We could have used one large hub or switch, but didn't have a box of Cat5e to make our own cables.
    10baseT is good for 100M (338ft) lengths, must have been a huge classroom! I wonder why you're teacher was running into issues. The setup was within the Ethernet 5-4-3 rule. Some hubs have a dedicated uplink port that needed to be configured either through the use of dip switch or through software. Perhaps that is the issue he/she was running into?

    Leave a comment:


  • GiGaBiTe
    replied
    Originally posted by Chuck(G) View Post
    No, I've seen them--this is some sort of silicone sealant injected into the plug void. It's usually quite visible as a white substance.
    Sounds like dielectric grease. I use that stuff in RJ45 connectors in harsh environments, it keeps the connector from corroding by keeping moisture out. It's especially important to use it in PoE applications, 24/48v causes things to corrode to hell real quick.

    Originally posted by kc8eyt View Post

    Remember this was 1998 when 10/100 was still the norm and the Pentium MMX and Pentium II was new tech. I agree no more than 10 systems should be on a hub, but as I recall the main reason was for sharing a printer and a simple share on the teacher system to send/retrieve files. Switches were still pretty pricey.
    Yeah, switches were generally in the hundreds of dollars range when you could get a hub for like $50.

    I remember back in high school computer repair class we were trying to build up a 10/100 ethernet network and needed three switches to span the length of the shop (it was a very long room.) The teacher kept buying hubs despite us telling him we needed switches. Connect more than two hubs together and the whole network goes down. We could have used one large hub or switch, but didn't have a box of Cat5e to make our own cables.

    Leave a comment:


  • Chuck(G)
    replied
    Originally posted by kc8eyt View Post
    I was replacing lots of 10base2 networks in the mid to late 90s. One company had over 25 systems on 10base2 and it ran fine, just slow (obviously 10Mb). The 802.3 standard handles collisions pretty well.
    You have to wonder if pulling out all that coax and replacing it with 4 twisted-pair unshielded cable was really necessary. After all, 2wIP used in industrial applications can handle 150 Mbps over 600 meters--and can even include PoE. 2wIP isn't fussy about cables. Single twisted-pair or coax are just fine.

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by Chuck(G) View Post

    No, I've seen them--this is some sort of silicone sealant injected into the plug void. It's usually quite visible as a white substance.
    I once looked into how "pre-made" cables were made. I also noticed that it seems some of them had some sort of sealant injected into them. It seems that all pre-made cables either came from China or Taiwan, so I just told my students it was 10,000 10 year olds in a sweat-shop in China making them for us. All the more reason to learn how to make your own cables. Think of the children!

    Leave a comment:


  • kc8eyt
    replied
    Originally posted by GiGaBiTe View Post

    I would have put it down to using a hub for 20 computers. The amount of reflections and collisions would have been so terrible that it'd be a miracle if it worked at all. A hub with even 4 computers on it has terrible problems with packet collisions. There's a reason why hubs stopped being a thing 20 years ago..
    Remember this was 1998 when 10/100 was still the norm and the Pentium MMX and Pentium II was new tech. I agree no more than 10 systems should be on a hub, but as I recall the main reason was for sharing a printer and a simple share on the teacher system to send/retrieve files. Switches were still pretty pricey.

    Reflections usually only happen when you have open cable ends (for instance not terminating 10base2 with 50 ohms on each end). Reflections are a thing of the past with 10baseT.

    I was replacing lots of 10base2 networks in the mid to late 90s. One company had over 25 systems on 10base2 and it ran fine, just slow (obviously 10Mb). The 802.3 standard handles collisions pretty well.

    Leave a comment:


  • Chuck(G)
    replied
    Originally posted by GiGaBiTe View Post
    Premade cables had something inside the end connectors? Those are usually injection molded so some plastic will get forced inside the connector if they let the moulding machine run too long.
    No, I've seen them--this is some sort of silicone sealant injected into the plug void. It's usually quite visible as a white substance.

    Leave a comment:


  • GiGaBiTe
    replied
    Originally posted by kc8eyt View Post

    This funky wiring scheme is done to prevent cross-talk between the wires. When I took over managing a local computer store in 1998 a previous tech had just installed a small hub based Ethernet network in a 20 computer classroom at a local church. They were complaining that things were slow and not working most of the time. The tech, not knowing EIA/TIA standards did exactly what you suggested. When I corrected the wiring everything went smooth after that. I always used that as a real-world example in my classroom of the importance of eliminating cross-talk in cabling.
    I would have put it down to using a hub for 20 computers. The amount of reflections and collisions would have been so terrible that it'd be a miracle if it worked at all. A hub with even 4 computers on it has terrible problems with packet collisions. There's a reason why hubs stopped being a thing 20 years ago.

    Originally posted by g4ugm View Post

    never needed super glue. I only had a problem were some cables had some sort of sealant in the plug.
    Premade cables had something inside the end connectors? Those are usually injection molded so some plastic will get forced inside the connector if they let the moulding machine run too long.

    Leave a comment:


  • Chuck(G)
    replied
    There are also RJClips
    Made in Canuckistan.

    Leave a comment:


  • g4ugm
    replied
    Originally posted by kc8eyt View Post

    I've never seen these. Do they fit snugly or would a drop of super glue help?
    never needed super glue. I only had a problem were some cables had some sort of sealant in the plug.

    Leave a comment:

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