Rack Mount Cable Modem

My cable modem (an Arris Surfboard SB8200) has been sitting on top of my Unifi Dream Machine Pro in my rack for a while now (maybe even a few years). Occasionally it would get bumped or even tip over but generally it was in the way and taking up a vacant 1U slot without much good reason. Well, no more. I finally had enough and converted a standard SB8200 into a 1U rack mount version.

This isn’t a step-by-step guide and it assumes some knowledge and tool ownership.

Supplies:

Tools:

How it all comes together:

The first step is to crack the modem open. These are surprisingly tough to get into. The single torx screw on the rear needs removed, the label needs peeled from the bottom, then it’s ready to pry.

Let’s start by taking a look at a side of the fully disassembled case:SB8200 Side Case

The top is to the bottom right of the picture with the front to the right. You can see the tabs at what would be the top center when assembled. I pried the case apart with a plastic spudger until I could push on the tab with a popsicle stick and a pocket pry bar – a flat blade screwdriver would work well too. The next place to attack is the bottom. Your choice if you save the label to re-use but either way, make sure you write down or take a picture of the MAC address so you can activate the modem with your provider. Peel back the label until the holes become visible:Bottom of SB8200 with label peeled back to reveal hole

Insert a tool into the hole to push on the tab until it releases. Repeat for both holes. The case should be more separated than not by now but keep working it apart until just front bezel is holding everything in place. On the side of the case not holding the modem PCB, you can get in and release the tab from the latch to fully separate the two halves.Half of an SB8200 showing the tab

For the other one, use your favorite pushing and prying tool to reach through a vent hole in the side and release the tab from the latch:Side of SB8200 showing front bezel tab and latch through vent holes

At this point, you should have half the case with a PCB firmly stuck in it. There isn’t a great method to get it out other than some careful prying and pulling. If you slip and hit the case with the PCB on the way out, it will likely knock some SMD capacitors off which will require finding the one you can and soldering it, along with a new one, back in place under your microscope.

Once free, the nut and plate can be removed from the port side of the modem PCB.

Back side of SB8200 showing ports

The free SB8200 PCB. Don't mind the black lead weight, it just keeps the PCB from tipping forward.

That was the hard part, now time for the careful and slow part.

I started with the most visible part first so if I messed it up the whole thing would look bad. First step was to measure the Black Box bezel so I could lay out the hole on the front plate.

Front plate and hole template

This template confirmed fitment and allowed me to mark the lines and holes.

Marked front plate

The key is to make sure it is centered vertically then drill in the corners with a 1/8″ drill bit (which I cleverly wrote by the holes so I wouldn’t make a silly mistake. Next, the two mounting holes are drilled with the 2.50mm drill bit and tapped to M3 for the mounting screws.

The interior was opened up with a larger step drill bit. I would recommend using a regular drill bit to get a cleaner hole.Front panel opened up with step drill

From there, it’s a matter of cutting away a bit with a hacksaw or just filing it down. The aluminum moves pretty fast but take your time to get the sides straight and square. As you get close to the line, test fit the bezel until it just slips into the hole. Next ones will likely be laser cut to avoid all of this.  Once you’re done, this is what it will look like:Front panel with bezel hole. Clearly missing the mounting holes because I didn't have the right size drill bit on hand when I started.

All finished with the bezel screwed in place:

Front panel with the bezel screwed down

 

I’m not going to show the LED holes in the center up close because I found out afterwards they were done with a dull bit and look quite rough. And I forgot to take a picture of them. Basically, line up the PCB where it needs to go in the enclosure, measure the height it will sit at when done, and drill 4x 5mm holes on 10mm centers. This step should probably wait until the threaded standoffs are inserted but I changed my plan and had the PCB semi-mounted on plastic standoffs, drilled the holes, then changed my mind to the metal press-fit standoffs. Just wait then measure so they line up.

As close as we get to the front LED holes

Time for the back of the enclosure. First up is the IEC inlet. Same as the bezel, measure, make a template, mark the metal, cut it out.

IEC inlet template

This metal is quite thin so be careful when drilling the 1/8″ holes in the corners. Same as before, use a bigger bit to open up the center then use files or a nibbler to remove waste to the line. Again, test fit as you go to keep it tight and clean.

IEC inlet in place

The female to female F coupler gets mounted in the back as well. Originally, I was going to have it centered in the back and use a short coaxial cable to connect the two. Difficulties measuring and crimping led to plans changing.Original plan

To solve the problem, I drilled a series of holes to allow mounting in several places plus increasing airflow. Definitely meant to do that. Showing the holes in the back

There isn’t a great way to mark the locations for the holes for the threaded standoffs but it starts with putting the PCB in place in the enclosure, kind of eyeballing where the holes would be, marking them, and comparing it to a tracing on paper.Top down view

 

Once the holes are drilled, the standoffs can be pressed in. These are flush on the bottom and there is no hole – they deform the metal around the hole into a groove on the standoff to lock it in place then deform to drilled hole into a hex to keep it from rotating.Standoffs installed

Once all the metal work is done, the power supply can be stuck down using the double sided mounting tape. The power supply fits nicely in the front left corner in front of the IEC inlet beside the PCB. It is just short enough to fit under the cover. Once mounted, the IEC inlet can be wired up and connected to the power supply. The easiest option to power the modem is to cut a few inches of wire with the plug off the SB8200 power cord, crimp terminals onto the ends, and use that to connect the power supply to the modem.Power supply in place

After connecting the RJ45 jack and coaxial cable, it’s time to tie everything down so it won’t bounce around. I used self adhesive cable tie mounts in two places to hold it all in place.Everything done and tied down

To finish it all off, I carefully peeled the face plate off of the SB8200 bezel and cut it apart to have just the LED section.

Covered up the ugly holes!

Here it is all done in the rack. I also cut out the Surfboard SB8200 emblem and put it on the front. These will be getting updated at some point so it looks better. It’s not an exact match to the Unifi silver but all I did was brush it with a Scotchbrite pad and spray it with satin lacquer – paint to follow some day.All Done

 

 

If all of this is too much work and you want me to build one, check out my store. Yes, it is expensive but the parts are expensive and it takes a lot of work plus I just explained how to do it yourself.

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