The Eccentric Workshop Blog

Rack Mount Cable Modem (SB8200)

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:

• 1x Arris Surfboard SB8200 Modem
• 1x BUD Industries CH-14401 Aluminum Small Rack Mount Chassis – 19″ L x 8.12″ W x 1.75″ H
• 1x BUD Industries C-14431 Aluminum Small Rack Mount Ventilated Chassis Cover – 17″ L x 8″ W x 0.05″ H
• 1x MEANWELL RS-25-12 AC to DC Power Supply, Single Output – 12V, 2.1A, 25.2W
• 1x Black Box Panel Mount Modular Coupler (FMT1081 or FMT1020)
  • OR 1x Black Box Panel Mount Bezel (FMT1000) and 1x RJ45 Keystone Jack
• 1x F Jack Female to Female Coupler
• 1x IEC Inlet – switched or not
• 1x 1′ Cat6 Cable
• 1x 1′ Coaxial Cable with F Connectors
• 3x M3 x 10mm Press-Fit Threaded Standoffs (PEM Inserts)
• 3x M3 Nylon Screws
• 3x M3 Nylon Washers
• 2x M3x8mm Screws
• Scotch Double Sided Mounting Tape
• Misc. wires and terminals for connecting IEC inlet to power supply
• Misc. supplies to secure wiring (self adhesive wire tie mounts, cable ties)

Tools:

• Misc. plastic case opening tools
• 4.2mm Drill Bit for Standoffs
• 2.50mm Drill Bit and M3 Tap
• Sheet Metal Nibbler
• Misc. other drill bits (1/8, 3/8, 1/2)
• Needle files – don’t go cheap but top of the line is needed either
• I used a drill press but the holes can easily be drilled by hand as well with some care.
• Inserting the press-fit threaded standoffs requires about 1,000 pounds of force to fully seat them.

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:

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:

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.

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:

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.

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

First step was to measure the Black Box bezel so I could lay out the hole on the front plate.

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

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.

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:

All finished with the bezel screwed in place:

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.