Capacitor on Smart Home? Sure — But Secure!

Repairing BROKEN Shellys – the 30 CENT Fix That Actually Works!

Sun, 21 Sep 2025 00:00:00 +0200

Is your Shelly 2.5 humming? Making strange noises or constantly dropping the Wi-Fi connection? Then you are probably familiar with the frustrating problem that many Shelly owners face: after a few years, these devices become increasingly unreliable.

What looks like a Wi-Fi problem at first usually has a completely different cause. The good news: in most cases you can fix it yourself with a 50-cent repair!

To load the video, please click the image. Please note that by doing so, data will be transmitted to YouTube.

The Problem: When Shellys Get Old

Recognizing the Typical Symptoms

Shelly 2.5 devices of the first generation in particular show characteristic problems after a few years:

Strange noises: Humming or buzzing from the device
Unstable Wi-Fi connection: Sporadic disconnects
Unreliable operation: Commands are not executed
Complete failure: The device stops responding entirely

In the video I demonstrate the characteristic sound — if your Shelly sounds like that, there is a good chance this repair will help!

The Root Cause: Capacitor Aging

What many people do not know: the problem is usually not the ESP8266 chip or the antenna, but a tiny electrolytic capacitor in the power supply. After years of use, it loses its electrical properties and destabilizes the entire power circuit.

The tricky part: the capacitor looks completely normal from the outside — no bulging, no visible damage.

The 50-Cent Repair, Step by Step

What You Need

100µF/16V electrolytic capacitor (approx. 50 cents)
Soldering iron and solder
Narrow flat-head screwdriver
Some patience and care

Important safety note: Never work on the Shelly while it is connected to mains power!

Opening the Case — the Flat-Head Screwdriver Trick

Opening the Shelly 2.5 is a little tricky, but perfectly doable with the right approach. In the video I show you exactly:

Where to insert the flat-head screwdriver
How to carefully pry off the casing
What to watch out for with the delicate tabs

The trick is to work systematically along the sides without applying too much force.

Identifying the Faulty Capacitor

Once opened, you can see the compact circuit board with all its components. The problematic capacitor is the small black cylinder marked “100µF 16V”. In the video I explain exactly:

Where the capacitor is located
How to distinguish it from other components
What other capacitors are present on the board

Removing the Faulty Capacitor

Desoldering requires some skill, but is very manageable with the right technique. I show you in the video:

How to carefully tilt the capacitor out
The correct soldering iron technique
How to clear the holes after removal

Particularly important: the capacitor sits on the outer edge of the board and is therefore relatively easy to reach.

Installing the New Capacitor Correctly

With electrolytic capacitors, polarity is critical:

Negative pole: Marked with a broad stripe on the casing
Positive pole: The longer lead

In the video I show in detail how to correctly identify the polarity and orient the capacitor. Getting this wrong would destroy the entire device!

Reassembling the Case

When reassembling, make sure to route the Wi-Fi antenna correctly. There is a dedicated notch in the case for it — the video shows you exactly how this works.

The Success Test — Live in the Video

The most exciting moment: switching it on for the first time after the repair! In the video you can watch live:

How the repaired Shelly boots up
Testing the web interface
Checking the relay function
And most importantly: the listening test reveals complete silence!

After a successful repair, the Shelly will run reliably for years to come.

Other Affected Shelly Models

The capacitor problem is not limited to the Shelly 2.5. Other models can be affected as well:

Shelly Dimmer (first generation)
Shelly 3EM (older versions)
Other first-generation Shellys

The repair principle remains the same — only the exact capacitor type may vary.

Why the Repair Is Worth It

Sustainability over the Throwaway Mindset

Instead of discarding working hardware and buying new devices, you invest 15 minutes and 50 cents in materials. That is:

Environmentally friendly: Less electronic waste
Cost-saving: A new Shelly 2.5 costs over 20 euros
Educational: You understand your hardware better

Long-Term Reliability

After the capacitor repair, the Shellys work like new again:

Stable Wi-Fi connection
No more strange noises
Reliable response to commands
Years of further trouble-free use

Practical Tips for the Future

Preventive Measures

Electrolytic capacitors age faster due to:

Heat: Avoid excessively warm installation locations
Moisture: Ensure a dry environment
Overvoltage: Use surge protection

When Is a Repair Worth Attempting?

The repair is most promising for:

Devices older than 2–3 years
Typical noise problems
Sporadic Wi-Fi dropouts
Devices that are still partially functional

More Hardware Repairs

This repair impressively demonstrates that smart home can be sustainable! The video shows not just the practical implementation, but also my thought process during troubleshooting.

More Repair Guides

Repairing a Sonoff S20 Smart Plug – the 26-Cent Fix – The same capacitor problem, different device: fixing Wi-Fi disconnects on the Sonoff S20
Replacing a Tablet Battery Yourself – Save Your Old Device in 20 Minutes! – When the tablet used as a smart home dashboard only works while plugged in

Note: Links marked with affiliate link are affiliate links. As an Amazon Associate I earn from qualifying purchases. This means I receive a small commission if you purchase through these links — at no extra cost to you. The revenue helps me run this blog and YouTube channel and keep creating content. Thank you for your support!
― Joachim

Repairing the Sonoff S20 Smart Plug: The 26-Cent Fix

Sun, 07 Sep 2025 00:00:00 +0200

Sound familiar? Your Sonoff S20 smart plugs worked reliably for years, but suddenly they keep dropping their WiFi connection. A restart fixes things — for a few hours. Then the same thing happens all over again. You simply can’t build a reliable smart home on devices like that.

The good news: in most cases you can fix the problem yourself for under a dollar in parts. The secret lies in a tiny component that loses its electrical properties after a few years.

To load the video, please click the image. Please note that by doing so, data will be transmitted to YouTube.

The Common Problem: Unstable WiFi Connection

Recognizing the Symptoms

The problem tends to show up in a very characteristic way:

The Sonoff S20 sporadically drops its WiFi connection
After a restart everything works again for minutes to hours
The device stops responding to commands from the app
The LED blinks irregularly or shows error states

The Root Cause: Capacitor Aging

What looks like a WiFi problem at first glance actually originates in the plug’s power supply. After some research it became clear: the electrolytic capacitors used in these devices lose their rated parameters after a few years.

This causes instability throughout the entire power supply circuit — instability that the ESP8266 microcontroller cannot handle. In the worst case the device eventually dies completely.

The $1 Repair: Step by Step

What You Need

One 330µF/16V electrolytic capacitor
A soldering iron and some solder
A Phillips screwdriver
Desoldering braid (helpful but optional)
Common sense when it comes to safety

Important safety notice: Never work on the plug while it is connected to mains power!

Opening the Case

The Sonoff S20 is surprisingly easy to open. Remove four Phillips screws and you have access to the circuit board. The video shows you step by step exactly where the screws are located and how to open the case safely without damaging anything.

Identifying the Culprit

The problematic capacitors are easy to spot. They are the electrolytic capacitors in the power supply area of the board. The main suspect is the 330µF/16V capacitor located between two IC chips.

The tricky part: these capacitors look completely normal from the outside. No bulging, no visible damage — yet they are faulty. The video shows you exactly where to find the suspect capacitors and how to tell them apart from other components.

Removing the Faulty Capacitor

To replace the capacitor you need to partially loosen the board so you can reach the solder joints from the back. The relevant contacts sit between the two chips and need to be carefully desoldered.

The video shows the soldering iron work live, including tips for avoiding damage to the board. Clearing the holes after removing the old capacitor is covered in detail — that is the trickiest part of the whole repair.

Installing the New Capacitor

When inserting the new 330µF/16V electrolytic capacitor, polarity is critical:

Negative lead: Marked with a thick stripe
Positive lead: The other side (longer leg)

The board markings show you exactly which way the capacitor goes. Positive on top, negative on the bottom — following the markings on the board. The video demonstrates slowly and clearly how to identify the correct polarity and align the capacitor properly. Getting this wrong would destroy the entire power supply!

Reassembly

When reassembling, pay close attention to the correct positioning of the button. The small transparent plastic piece must sit precisely on its pins, otherwise the manual button will no longer work.

Also make sure the cables are routed so they do not conflict with the socket contacts. The video shows the small but important trick with the button — miss it and you will regret it later!

The Moment of Truth

After screwing everything back together comes the exciting part: the first power-up. If everything was done correctly, the LED starts blinking happily and the plug connects to the WiFi without any trouble.

The video shows the successful result live: the repaired Sonoff S20 is fully reachable at its IP address and switches flawlessly — something that was not possible before. That moment is genuinely satisfying and proves the effort was worth it.

Why the Repair Is Worth It

Sustainability Over Throwaway Culture

Instead of throwing away the “broken” plug and buying a new one, you invest about 30 minutes of time and under a dollar in parts. That is not only sustainable — it is also educational.

Other Affected Components

If replacing the first capacitor does not solve the problem, the other electrolytic capacitors in the circuit may also be affected. The repair principle stays the same.

Long-Term Stability

After the repair the plugs work perfectly again. The WiFi connection is stable, response times are fast, and reliability is back to its original level.

Practical Tips for the Future

Prevention

Electrolytic capacitors age due to heat and operating time. Avoid placing your Sonoff devices in excessively warm environments and ensure adequate ventilation.

When Is a Repair Worth It?

For devices older than 2–3 years that show the WiFi problems described above, a faulty capacitor is very likely the cause. The repair is usually successful and only takes a few minutes.

More Hardware Repair Projects Ahead

This repair shows impressively how sustainable smart home can be. Instead of discarding working hardware, we fix it with minimal effort. The best part: the video shows not just the repair itself but also the reasoning behind it — what to look for when diagnosing the fault and which pitfalls to avoid.

More Repair Guides

Fixing BROKEN Shellys – The 30-Cent Repair That Actually Works! – The same capacitor principle applied to the Shelly 2.5: solving WiFi problems with a new capacitor
Replace a Tablet Battery Yourself – Save Your Old Device in 20 Minutes! – When your old tablet needs to last hours instead of minutes as a smart home dashboard again

Note: Links marked with affiliate link are affiliate links. As an Amazon Associate I earn from qualifying purchases. This means I receive a small commission if you purchase through these links — at no extra cost to you. The revenue helps me run this blog and YouTube channel and keep creating content. Thank you for your support!
― Joachim