Custom Cables


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Okay, I finally have the pieces to build custom power cables for my Norco and I think I will be shortening the main motherboard power cable by about 3 feet too. However I have a question - what gauge wire for the leads? I ordered wire in what I think was 18 gauge. It appears a little thin and isn't copper - it's silver in color. I happen to have a couple of spools of 16 gauge from Waytek (awesome source for wiring!) and was considering using it but I only have yellow in 18. The jacket on the Waytek is way tougher and it's also copper wire.


What gauge is stock wiring? Copper vs the silver stuff? Considering soldering the pins that go into the PSU, the rest look like the type that you punchdown. Both gauge look like they would work...



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The "silver" wire could be tin-plated copper or it could be aluminum. You can tell be knicking it with a knife or cutting the end square and if the "silver" color is only on the surface it is plated. Conversely if the color is through out then it is aluminum.


As far as gauge goes, there are a few things to consider. What gauge wire are your connectors designed to work with (min-max or just one size) the loads you are considering putting on those particular runs you create and the insulation of the wire you are that order in my opinion. First, if your connectors are designed for 18-22awg wire then 16 will not fit, etc. Second, 18awg wire is rated to carry 16amps and 16awg is rated to carry 22 amps, both in an open air configuration (which the inside of your computer case is as opposed to together under a single insulation like a cord for a vacuum for instance). So for each "run" you are considering making, calculate how many amps that circuit will need to support, i.e. green drives draw about 2 amps each and fast spinners draw about 3 amps each. Multiply by number of drives and there is your rough amp draw total per "circuit" you are planning to make.


Just a rough and quick guide to keep things safe inside your expensive box

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24 drives total, few if any greens. Two runs of connectors. Naturally it's the yellow 12volt I don't have in 16gauge! I may have white though, I'll look tonight. I believe the connectors can handle the 16 fine. I suppose larger is safer anyway. I may solder at the PSU end just to cut resistance, crimping seems iffy there.


I've seen silver that seemed like it was stainless. Very shiny and tough. I don't think this stuff is tinned copper but in any case it seems thin to me. Don't want to take chances. The punch down Molex seem like they will drop voltage so I'll use the copper in a beefy gauge.


Got to do something to shorten and clean things up. The motherboard leads will be the worst to do!

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If you are going to solder the leads, tin coated wire is much easier to solder because tin oxide is much to 'clean' with non-corrosive flux than copper oxide.  Obviously, only solder with non-corrosive flux should be used in computer applications.  I would be most careful about the choice of any crimp connector on 5 and 12 volt, high amperage circuits.  Connections that are entirely satisfactory at 110 volts may not work well with those lower voltage.  A half voltage drop at 110 volts is not a big issue, but that it can lead to serious reliability problems with low voltage equipment.  This has always been one of the big knocks on Molex connector breakout cables.

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Well it looks like I'm back to 18gauge wire. For starters it seems I have the whole Waytek catalog in 18gauge and only red\black in 16. The 16 is also looking marginal for fitting into these crimp on connectors on the PCU side. I'd have to crimp right to the copper with nothing grabbing the jacket which is a recipe for disaster. The connectors I'm using are the same thing that Seasonic uses - I believe they crimp too. I'll have pairs of wires per connector so I think the amperage will be fine.


I'm not sweating the solder part, I've got a nice station and decent solder for the job. Tinned wire would be easier but I'm not certain this stuff is tinned and it would likely wick the solder up into the wire far easier, the silver stuff also has a far wimpier jacket - the Waytek wire is bulletproof. I've dealt with the results of high resistance Molex connectors in a past life having had to replace quite a few power leads as a result so I know I'd like this working with little voltage drop.  I'm most worried about the punchdown connectors honestly.


All of the connectors I'm using are the same stuff the factory guys are using and was sourced from either FrozenCPU or modDIY for this project. Looking at some of the wiring I've got around I could probably have pirated quite a bit of the punchdown type connectors from PSU leads here but this is all new. I'll sleeve and heatshrink it when done and snap a pic of it all. I'll be shortening the motherboard leads one by one which will be painful but I've got a new connector and pins for it set to go, not sure I'll be able to shrink that one however.

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I've never liked paralleling where I could avoid it. If one wire weakens breaks or otherwise becomes disconnected your system will be pulling the amps from one wire only, potentially causing a meltdown or fire.


That being said most PSUs use 18 gauge to peripheral connectors. I checked my seasonic 750 and it indeed uses 18. It may be worth a trip to a local hardware store for some 16 gauge though.

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Okay good to know it's 18 on others at least! As for parallel cables, each connector appears to use pairs so there's no getting around it, I didn't mean I'd try to run dual cable to each connection. While maybe possible it would be tough and the punch downs and the pins at the PSU aren't large enough to easily allow it. The caps at the Molex also might not be able to be snapped in doing that, I'll have to look.

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Sorry, I didn't know what you meant by doubled or pairs as you posted earlier but now I get what you meant. If I had known , I would have pointed that out for you that the yellow is the 12v wire and red is 5v, both blacks are grounds (they have to carry the current back for each of the positive wires so you can't cut that wire out unless you are not using one of the positive sources).

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Right, I understand the paired grounds etc and understand the reasoning - I just thought that there were multiple hot leads and there aren't. This means that yeah the 18gauge wires will be carrying some current. I'll power both Molex to try and reduce load.


It does occur to me that I'll have to trace the current ground wires and make sure I don't cross them since ground for 5volt may not match ground for 12! It probably wouldn't matter but ground isn't always equal, found this out the hard way working on cars.

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IIRC all grounds in a power supply are common (go to the same place). The commons in a PSU normally go to one or two screws near where the three prong plug goes into the PSU inside the case, which of course is grounded to the case. This is so everything has a common ground eliminating ground loops inside your system and a common reference for all components.


As for all grounds not being equal, this is true to an extent. A bad ground can cause overvoltage(which leads to too much current). This happens when the resistance changes and is why a common ground is desired. Given the same gauge wire, one section grounded at the front of the car and one in the trunk, both should have the same resistance. If one is dirty or not connected directly to the bare metal, it raises the resistance which can cause problems. Also, In a car you are (almost) always working with the same voltage, but different amperage. Given a good clean ground, its usually the wires that lead to the ground not being equal in a car that causes overheating. The chasis in a car is your common ground(which is why the negative terminal also connects to the chassis).


Since your 12v, 5v and grounds are the same gauge wire and have the same common ground, each lead can handle the same amount of amps and voltage.


Hope Im not telling you stuff you already know, if not I hope you leave with a little better understanding. I could explain it better but I don't think your after a full course in electrical theory lol.



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Well, I paired grounds with power leads consistently just in case. I'm running into an issue with the punch down connectors. The jacket is tough enough that I suspect not all connections are solid and I can't find my multimeter yet to test continuity :-(


I had thought to have some slack between backplanes and loom the wires. In practice the wire is too stiff for that with these connectors. I'll be doing straight runs up the backplanes sans loom in between, first one ive built has a slight wrinkle but I suspect the second will look great. Best to start at the top and work down I think, do the PSU connectors last. This is in a Norco 4224 case btw. I did at least move to shorter SAS cables, 3ft cables were just crazy long!


Doing the mobo connector and the smaller CPU power connector will wait a bit. The smaller connector doesn't look bad but the mobo one is a beast!



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Heh, yeah that was stuff I knew ;-) My experience with cars was with tuning them, more specifically tuning the EFI. Issues arise when a sensor isn't given a dedicated ground from the ECU, like say an aftermarket wideband O2, when it's ground reference is different from other sensors. These get powered from the battery not ECU and have their own voltage regulation, you can see the potential issues coming. That's one sensor you want as accurate as possible too!


I wasn't sure if the internal guts of a PSU were all grounded together, though common sense says they ought to be. I wouldn't want my 12volt to be 13 simply because I chose to use the 5volt ground :-O A voltmeter placed on both grounds would solve the question but of course that's the tool I'm missing - argh! I was forced to redo one connector, the end most one, and when I did so I can see penetration issues with the connector and the tough wire jacket. There could be something to be said for not using abrasion and chem resistant wire here :-(


I would advise starting at the end most connector trimmed tight so it can be capped, then working towards the PSU with some extra length. The braided cover also likes to come apart, before cutting you can wrap it with tape and cut through the tape - much like braided steel hose on a car. This keeps the braid from fraying and allows you to slip heat shrink over the end easily.


Not yet sure how I'll do the 24pin beast. I will need to cut the braid off then snip and terminate each wire I think. If all I care about is the right wire color and not specific wires then this becomes tons easier! Based upon the ground conversation I suspect wiring order is way less sensitive than I feared and that colors aligned correctly is important, I could cut them all at once if that's the case. Anyone know for sure or done this?

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  • 1 month later...

So I FINALLY got the cables done for my system in a marathon session of cutting, crimping, and soldering last night - whew! I shortened the main power cable to the mobo - a 24pin monster, the "CPU" power cable that has six pins, and I built a second power lead for my Norco backplane - not as easy as it sounds.


Lessons learned...


The main power lead is a PITA, if you need a shorter or longer one buying one if you can find it might not be a bad idea. I wasn't sure how to approach this one to start with and figured I'd just snip and shorten one wire at a time. Except that this makes putting on heatshrink over the covering impossible. I then bit the bullet and just cut the cable all at once. I figured that so long as I matched up colors no biggie right? Well sorta'... If you look closely you'll find that some slots have two wires in them, two wires are twisted together through the harness, and that there are at least two gauges of wire in the harness - argh! My eyesight for working that close also isn't what it used to be so I had a good flashlight and a magnifying glass to help but my workspace still sucked - my kitchen table. You can read the gauge of wire on the insulation if you look closely so that helped. Red and Orange were a little hard to tell apart but I got that. You will also notice that one pin is empty, don't screw that up. I worked one wire at a time and ended up using needlenose to crimp the pins. Be advised that these pins have two guide ears that you want to keep and that the pins orient a specific way, shine a flashlight into the connector to see the guide grooves. Once you figure out orientation and not to flatten those ears life is MUCH easier! Before cutting back the mesh covering the bundle wrap some tape around it approximately where you'll be heatshrinking it and where you make the cut if possible - this keeps it from fraying and is how you handle braided hose on race cars. Once the bundle is cut slip some heatshrink over it and slide it back over the tape - fairly far back out of the way. The tape on the cut end will help this, if the covering frays pushing heatshrink over is impossible. Get big enough heatshrink and get good stuff, the stuff with glue in it would be ideal. I did the wires one at a time one up, one down working across the connector. I snipped the spare wire off the pigtail as I went to help keep track - it sucked! System fired up fine though thankfully. Test fitting the mobo connector before starting is a good idea and maybe test fit a few times as you go to make sure the pins are seated and happy. The "CPU" wire was cake after this!


Wiring the backplanes... This was done with multiple passthrough Molex and a capper Molex on the top. The best way to do this is to cut a set of wires long, place a cap connector on top, plug it in, lay the wires down, and mark the next one to be punched into a connector. The spacing is just over an inch apiece. Too short and the connector won't plug in to the next board, too long and it will be hell trying to bend the wires and get it into the backplane. I used wire with a heavy duty jacket that made bending short lengths more difficult which was a mistake. Keep the connectors parallel, at least two of mine are slightly cocked. I used a flat bit screwdriver to punch down the wires and had to smack it a few times to drive them down. Go slow and check the fit  after each connector. Once the backplane part is done slip sleeving and two heatshrink over the pigtail and measure for the PSU distance. Terminating that end is cake if you've done the above! Check continuitiy with a meter on all connectors starting at the top and working down before capping these little beasties as that is a hassle.


Once you've done all this do a Snoopy dance! In my case I removed at least 6-7 INCHES of wire from the power connector to the Mobo, more than that to the CPU power which was folded on itself like an accordion, and the power runs to my backplanes are CLEAN with no adapters in sight but R&R'ing these will be a major hassle should I ever need to!


I still have SAS wires that are a little long, I ended up stuffing a full size spinner drive in near my PSU as well as an SSD, and the fan wiring is all over the place too but it's still way better than before IMO. Glad I did this, glad nothing smoked, but I sure wouldn't want to do this again anytime soon without a damn good reason to. If someone finds a source for custom length Mobo wiring I'm all ears let me tell you....

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Maybe here:


I actually bought some of my parts from those guys. However I couldn't find anything on there where I could state what cable I wanted for what PSU and at what length. If I could've simply said I wanted a 6inch long PSU to Mobo cable and gotten it for a reasonable sum I'd have considered it.


I'm looking over their site more closely now. I do see some cables I could've used listed like this one -> and but from the looks of it I'd be paying about $60 or more. I certainly recognize the bling factor with these cables and the individual sleeving is very pretty... I just wanted a shorter cable darn it, not something to show off :(


Having now done this job once I know what my time is worth and how long it took me. Yeah, I'd be tempted to pay the $50 for the 24pin connector just because it was such a PITA. If I was building a really pretty system with clear side panels and lights then for sure it would be worth it. Starting out and not having done it I think I'd have balked at paying $50 or more. One thing to consider too is that this shop ships from overseas and it took me about 2 weeks or so to get my connectors from them.

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