Cleaning the Stronghold s7x and s7pro

Disclaimer: none of the below is based on suggestions from Stronghold or any distributor. This is what I do and works for me. I feel the below is pretty safe for you and your machine if you take sensible precautions: unplug the Stronghold, be mindful of what connects to what, and take pictures if you aren’t sure.

Saturdays here at Ceto are prep days for production on Sunday. This is usually fairly light work: clean up and organization in the roasting room, rehydrating and defrosting coffees if needed, and seeing if we need to pull any bags or other supplies from storage. This Saturday however I wanted to do a deep dive into cleaning the s7x and decided to bring you along for the ride.

The question of “when should I do a deep clean of my machine” is a little subjective. There are some surfaces in these machines that will accumulate some seasoning even during light roasts. Personally, I do not mind the seasoning buildup in the drum. I don’t think it does anything good or bad for the roaster or your roasts -- unless it manages to build up so much where it prevents some of the moving bits from moving very well. What is an issue, outside of general cleanliness, is the buildup of chaff & dust (or even coffee beans!) in the exhaust path of the roaster. Even a small amount of chaff or a few old beans in the exhaust path will have a noticeable impact on the roast – your roasts will run a little hotter.

So, how often do you clean? Unfortunately, it’s pretty hard to visually inspect and equally difficult to access much of the exhaust path of the Stronghold. You can try to “look up the chute” with your phone camera (I believe this is Stronghold’s official inspection method), but I haven’t had much luck figuring out what is going on this way. One way you can start to get an idea is to take off the exhaust hose and peek in at the exhaust blower: if there’s chaff here at all, you definitely need to do a deep clean—things are starting to stick, and they will build up fast—potentially within just a few roasts. If it’s just a little dirty maybe blowing things out with some compressed air will work well enough.  

On the s7x and the pro, I suggest vacuuming out the easy to access areas of the roaster every production day, even going as far as to vacuum out up through the chaff collector, and doing a deep clean every 200-400 roasts—absolutely never exceeding 500 roasts. If you don’t clean, after a while you’ll “feel” something is up – chaff will be sticking around in the chamber a little longer, roasts will run a little hot (with all else being equal, primarily voltage being the same from roast to roast) and if things get really bad, you’ll notice some of the exhaust leaking out through the exhaust exit chute when dropping the roast, or even worse, during roasting. Outside of this being not so great for your health, it’s not good for the consistency of your roasts.

It amazes me how much accumulates here in just a relatively small number of roasts. This is a little nook behind the cooking tray that loves to fill up with chaff and roasted coffee. 

Cleaning the outside of the machine is pretty easy. With the machine off, I vacuum out the chaff collector—I have one of those “bucket” vacuums you can buy from Home Depot and the hose fits perfectly in the chaff collection grid—and also the “chute” where chaff falls from, making sure the hose reaches all the way into the exhaust fan, and finally the tray under the cooling tray & areas around the outside of the machine.

Cleaning the inside of the machine is a little intimidating, but not too bad. Tools you’ll need are a 4mm hex key (I like to use a 4mm hex ¼-inch drive socket with a small drive ratchet), a small Phillips head screwdriver (my favorite for this is one that I believe came with the install kit for my Google nest! Fits perfectly in my palm) a few different brushes are nice, a wide but short paintbrush is convenient but if you misplaced yours one that is used for coffee grinder cleaning is just fine, a paintbrush that has a long handle is very convenient as you’ll see later, a damp towel or some damp shop rags are nice to get things very clean of dust, a vacuum is a near necessity, and finally a mask – things will be a little dusty!

I forgot to take a picture of my Google screwdriver.

The first thing you’ll want to do is disconnect the exhaust for the roaster. If using the stock exhaust, this will include a white plastic ring that you won’t want to lose – it is vital for the stock exhaust locking mechanism to function properly.

Start the disassembly by taking the Phillips screws off the top of the Stronghold housing section that houses the tablet, and remove the top, being careful to disconnect the cooling fans.

Once the top is removed, you’ll clearly see that this section is split into two parts, a front that holds the tablet, and a rear section which is attached to the exhaust. We can get away with removing only the rear section for this maintenance. There will be a few screws on the bottom that you will have to remove, and while these were not on the s7x, on the pro there are a few screws “holding the sections together” and also one or two connecting the rear panel to the roasting chamber outer enclosure. Look out for these screws, remove them and put them someplace safe.

Once the rear panel is free, you’ll have to loosen the hose clamp on the exhaust fan. I keep the short length of hose attached to the rear panel as it is pretty easy to clean that way. Disconnect this, and place the panel off to the side.

Now we have to disconnect the exhaust fan. Fortunately, this is pretty easy. There should be two separate sets of wires going to the fan. If these are not numbered by Stronghold, I suggest marking them with a marker. You may also need to cut a zip tie here (I would suggest replacing this with something that is removable and will stand up to a fair amount of heat) to free both cables. Do so, and then look under the exhaust fan where it connects to the chaff separation chamber. Here you will see two Phillips screws – note the orientation of these screws in relation to the machine and remove them, freeing the exhaust fan.

 
Now the final bit of disassembly, removing the top plate of the chaff separation chamber which requires a 4mm hex key. Remove all four screws, noting or marking the orientation of the panel (it matters for how the exhaust fan is positioned) and remove the panel.

 

You will now be able to clearly see into the chamber. You’ll potentially notice a few coffee beans in the exhaust path near the exhaust temp sensor. There is a “lip” on the left of the chamber where the square hole connects to the chaff chamber, make sure you check here for beans and crud. You’ll want to thoroughly clean this area with the long brush & if you can vacuum it out and even wipe it down if you can manage it, anything stuck in here will cause you problems. Brush off the temp sensor too. Assume any surface you can’t see directly has a ton of crap on it and needs to be cleaned.

Next, vacuum, brush off, and wipe down the inside of the chaff separation chamber, and make sure to get under the lip where the surface screws into. You’ll have a ton to clean here. Knock whatever you want down into the chaff tray – it is easy enough to clean this out later.

Now let’s clean the parts we removed. First up is easy enough, the cylinder that helps separate the chaff needs to be cleaned off. You can see here there’s plenty of dust and crud on the surfaces. Vacuum it up and wipe it down with a damp cloth.

Now we’re almost done, just needing to clean the exhaust fan. This should be cleaned as thoroughly as possible. Chaff gets stuck in all weird places in this thing. You can see from the pictures how much chaff came out of what looked like not a super dirty fan. I honestly have no idea where it sticks in here, but you want to vacuum this well, and use your brush to clean each fin as best you can before reassembly. If chaff starts to build up on these blades it will do so pretty quickly, and airflow will become severely restricted.

Reassembly is pretty simple – just repeat the steps in reverse. The main thing is to align the plate where the exhaust fan connects to correctly, but you can’t really mess this up – if you have it wrong the fan will not be able to be connected to the exhaust, so you’ll just spend extra time lining it up properly.

Once reassembled it is a good idea to do a few test roasts using cheaper beans. Your profiles will likely drift very slightly, your machine may feel like it lost a little power as well due to the fact that exhaust is venting easier now. You may need to compensate by using slightly higher charge temps or just adapt the profile slightly. Unless your machine was extremely dirty the changes should not be too drastic.

Anyway – that’s it for this post! Hope this helps a few of you out there with cleaning the Stronghold. As always, happy to answer any specific questions – feel free to leave a comment or reach out to us through our contact form or Instagram.