Sooma tDCS Troubleshooting Guide

This Sooma tDCS troubleshooting guide helps patients and clinicians resolve the most common issues with the Sooma DUO tDCS stimulator. Use the sections below to diagnose and fix problems with the Sooma App, electrode contact, LED indicators, ComfoCable, and device errors.

1. Start here – Basic troubleshooting checklist

Before attempting any specific Sooma DUO troubleshooting step, run through this checklist first. It resolves the majority of common issues.

1. Power off the stimulator (hold the stimulator button until the device beeps and turns off).
2. Fully quit the Sooma App (do not just minimise it).
3. Check that the Sooma App is updated to the most recent version in your app store.
4. Restart the Sooma App.
5. Power on the stimulator (press the stimulator button for one second until you hear a short beep).
6. Connect the stimulator to the Sooma App.

TIP If you have already tried the checklist above and the problem persists, find your specific issue in the sections below.

2. Sooma App Troubleshooting

2.1 Sooma App does not find the stimulator

What you will see or experience: The Sooma App does not show the stimulator in the connection screen, or shows “searching” indefinitely.

What causes this: Bluetooth or location permissions may be disabled, or the stimulator is already connected to another device.

1. Confirm the stimulator is powered on. You should hear a short beep and see the Bluetooth LED lit (grey means not connected to any device, which is correct at this point).
2. Check app permissions: go to your phone’s Settings → Apps → Sooma App → Permissions and make sure Bluetooth and Location are both set to “Allow”.
   • If you cannot change permissions: delete the Sooma App, restart your phone, and reinstall from the app store to see the permission prompts again.
3. Check for other connections: the Bluetooth LED should not be lit blue. If it is, another device is already connected to the stimulator. Power the stimulator off and back on to clear the existing connection.
4. Restart both the Sooma App (close completely, do not just minimise) and the stimulator.
5. If the stimulator is still not found: uninstall the Sooma App, restart your phone, and reinstall from the app store.

TIP Keep your phone within 1 metre of the stimulator when connecting. Bluetooth connections can be interrupted by walls or other electronic devices.

NOTE For Android devices: location permission is required by the Android OS for any app that uses Bluetooth scanning, even though Sooma does not collect location data. The app will explain this in the permissions screen.

2.2 Sooma App is stuck at ‘device waiting for configuration’

What you will see or experience: The Sooma App displays “device waiting for configuration” and does not proceed.

What causes this: The app and stimulator have lost synchronisation. Disconnecting and reconnecting re-establishes the link.

Solution:

1. In the Sooma App, tap the menu icon (≡) and select Profile.
2. Tap the Bluetooth icon and press Disconnect device to disconnect the stimulator from the app. Reconnect the stimulator by selecting it from the device list.
3. If the message persists: fully close the Sooma App, power the stimulator off and on, then reopen the app and reconnect.

3. Sooma DUO stimulator troubleshooting

3.1 Component names

3.2 Device Indicators Reference

The stimulator has three small LEDs and a large ring light. Use this section to understand what each light means before troubleshooting.

Color indicators during startup (after powering on)

Color indicators during treatment preparation

Color indicators during stimulation session

3.3 Ring light stays orange

What you will see or experience: The ring light remains orange — it does not turn green.

What causes this: There are three possible causes depending on when this happens. Look at the Electrode LED (the middle icon) to identify which.

3.4 No treatment available

What you will see or experience: The ring light remains orange after the stimulator is powered on — it does not turn green or blue.

What causes this: The stimulator only runs sessions that have been assigned by Sooma or a clinician via the Sooma App. If no session is loaded, the device cannot proceed.

1. Open the Sooma App and log in. Check whether a session is shown for today.
   • Session is shown → tap it, then connect the Sooma App to the stimulator to transfer the session. The ring light should turn green.
   • No session shown → your clinician needs to update your treatment schedule.
2. If you are not using the Sooma App: the stimulator cannot run a session without a loaded protocol. Ask your clinician for support in adding more treatments.

TIP If your Sooma App or stimulator shows no upcoming sessions, contact your clinic or equipment provider. They can log into Sooma Portal to extend or renew your treatment plan.

3.5 Ring light shows magenta during contact check

What you will see or experience: After plugging in the ComfoCable and pressing the stimulator button to start the contact check, the ring light turns magenta rather than green.

What causes this: The ComfoCap or hair is too wet — excess saline or moisture between the two electrode sites is creating a short-circuit.

1. Remove the ComfoCap from your head.
2. Use a dry towel to dry the hair and scalp at both electrode sites.
3. Put the ComfoCap back on and press the stimulator button to restart the contact check.
   • Ring light turns green → good contact achieved. Press the stimulator button to start the session.
   • Ring light is still magenta → If all the LEDs are magenta as well, the device has encountered an internal error and should be restarted.

3.6 Difficulty getting good contact

What you will see or experience: The ring light remains orange during the contact check, or the Sooma App shows poor contact quality. The Electrode LED shows a steady orange.

What causes this: Saline has not yet soaked through the hair, the ComfoCap is not snug enough, or something is blocking contact between the Conductive Pads and the scalp.

1. Press the ComfoTrodes gently against the head.
   • Contact quality improves when pressing → the equipment is working correctly. The issue is between the scalp and the Conductive Pads. Continue with the tips below.
   • No improvement even when pressing, the scalp already feels wet and the electrode LED shows a stable orange → go to Section 3.8 (No contact at all).
   • Electrode LED is pulsing → go to Section 3.11 (ComfoCable not detected).
   • Electrode LED is not on → go to Section 3.4 (No treatment available).
2. Check for hair or skin products (gel, dry shampoo, conditioner, etc.) on the scalp at the electrode sites. These reduce conductivity. Wash and dry the area if needed.
3. Remove wigs, hair extensions, or artificial hair positioned under the ComfoTrodes — these prevent direct contact with the scalp.
4. Ensure the ComfoCap is the correct size and is snug. There should be no loose fabric between the two electrode sites.
5. Ensure that Conductive Pads are unused. Wait up to 10 minutes. It can take several minutes for saline to soak through hair. The scalp should feel damp under both ComfoTrodes before you start.

ComfoCap Sizing

When in doubt, choose one size smaller. A cap that is too large will have loose fabric between the ComfoTrodes, reducing pressure and contact quality.

ComfoTrode lifetime

• Each pair of ComfoTrodes has a lifetime of 3 months or 100 sessions, whichever comes first. Using them beyond this reduces conductivity.
• Darkening of the ComfoTrode surface during use is normal and does not affect stimulation performance.
• Inspect the metal nub on each ComfoTrode. If it feels loose, the ComfoTrode is damaged and must be replaced.
• Avoid using soap to clean ComfoTrodes. Soap residue may reduce conductivity.

ComfoCable inspection

• Gently flex and move the ComfoCable during the contact check. If contact quality changes as you move it, the cable may have internal damage.
• Unusual electric shock-like sensations during a session may indicate ComfoCable damage.

3.7 Stimulation keeps pausing automatically

What you will see or experience: The session starts but automatically pauses repeatedly. The ring light returns to orange and you hear a contact-lost alert (short – long – short – long beep).

What causes this: The stimulator automatically pauses when electrode contact drops below the required threshold. Unstable contact is the most common cause.

1. Follow Section 3.6 to improve and stabilise contact before resuming.
2. Check the ComfoCap is snug — loose fabric allows movement and contact loss.
3. Make sure the ComfoCable is not being pulled or stretched during the session.
4. After improving contact, press the stimulator button to resume the session.

3.8 No contact at all / Sooma App shows no contact quality

What you will see or experience: The Electrode LED shows a steady orange, and the Sooma App shows zero or no contact quality even when the ComfoTrodes are pressed against the head.

What causes this: The device does not have treatment loaded, connections may be loose or equipment may be damaged or worn out.

• Check the Electrode LED state:
  • Blinking / pulsing → go to Section 3.11 (ComfoCable not detected).
  • Completely off → go to Section 3.4 (No treatment available).
  • Steady orange → continue below.
• Check all connections: confirm both ComfoTrodes are fully clicked into the ComfoCable, and the ComfoCable is fully inserted into the stimulator’s electrode connector (the port on the bottom).

• Test the equipment directly: remove the ComfoCap and press the two ComfoTrodes face-to-face so their conductive surfaces touch each other.
  • Contact quality improves to green or magenta in the Sooma App → the equipment is working and the contact issue is between the scalp and the Conductive Pads. Go to Section 3.6.
  • Contact quality improves but does not reach magenta even pressing hard → the ComfoTrodes are worn out. Replace them.
  • No change at all → continue to next step

• Restart both the stimulator and your phone, then retry.
• Replace the ComfoTrodes. If contact quality improves, the ComfoTrodes were worn out or damaged.
• Replace the ComfoCable. If contact quality improves, the ComfoCable was damaged.
• If none of the above helps: contact Sooma support. The stimulator may need to be serviced.

NOTE About the face-to-face electrode test (Step 3): When you press the two ComfoTrodes directly together, the stimulator may show a magenta contact reading. This happens because the direct electrode contact creates a very low-resistance connection. This is expected during this diagnostic step and confirms the equipment is functioning normally.

3.9 Stimulation sensation is strong or uncomfortable

What you will see or experience: The tingling or warmth under the ComfoTrodes feels intense, burning, or uncomfortable.

What causes this: Stimulation sensation is directly linked to electrode contact quality. Poor contact concentrates the current at fewer points, making the sensation stronger. Improving contact typically reduces discomfort quickly.

1. Press the ComfoTrodes gently against the head. This usually reduces the sensation within seconds.
2. If discomfort continues: press the stimulator button to pause the session.
3. Check that the skin under both ComfoTrodes is intact.
   • Skin appears red, irritated, broken, or has open wounds → do not resume.
   • Skin is intact → follow the preparation tips in Section 3.6 to improve contact quality, then resume.

TIP Some tingling and warmth during a session is completely normal and is a sign that the stimulation is reaching the scalp. The sensation typically fades after the first few minutes as the saline soaks in further. If the sensation is burning or painful rather than tingly, pause immediately and check contact quality.

⚠ SAFETY NOTICE If you experience any intense adverse reaction, pause stimulation immediately by pressing the stimulator button. If symptoms persist after pausing, contact your clinician or Sooma support.

3.10 Visual flash or mild electric jolt during session

What you will see or experience: During stimulation, you briefly see a visual flash or experience a mild electric jolt sensation.

What causes this: This is harmless and is caused by a sudden disconnection of electrode contact during stimulation. An abrupt change in the stimulation current triggers a brief sensory response.

1. Check that the ComfoCable is properly inserted and has not become loose.
2. Ensure the ComfoCap has not shifted — reposition it if needed so it sits snugly.
3. Avoid bumping or disconnecting the ComfoCable or moving the ComfoTrodes during the session.
4. If this happens repeatedly: the ComfoCap may be too loose, or the ComfoCable or ComfoTrodes may be damaged. Follow the inspection tips in Section 3.6 before your next session.

3.11 ComfoCable is not detected

What you will see or experience: The Electrode LED blinks or pulses (does not stay steady orange or green). The ring light may remain orange or unchanged.

What causes this: The ComfoCable is not fully inserted into the electrode connector, dirt is blocking the connector, or the connector is mechanically damaged.

1. Disconnect the ComfoCable from the stimulator.
2. Inspect the electrode connector opening on the bottom of the stimulator. Check for visible dirt, lint, or debris.
   • If dirty: power off the stimulator first. Gently clear the opening with a clean needle or toothpick. Do not probe deeply or apply force.
3. Firmly reinsert the ComfoCable into the connector until it seats fully.
   • Electrode LED shows steady orange → cable is now detected. Proceed with the contact check.
   • Electrode LED still blinking → continue to step 4.
4. Inspect the inside of the connector: the small conductive plate should be visible, flat, and undamaged.
   • Plate appears bent, broken, or missing → the stimulator must be returned to Sooma for service. Do not attempt to repair it.
5. Test with a spare ComfoCable. If the problem resolves, the original ComfoCable is damaged and should be replaced.

3.12 Device shows internal error / All LEDs show magenta

What you will see or experience: All three LEDs (Bluetooth, Electrode, Battery) turn magenta simultaneously. The device may emit 2 beeps.

What causes this: The stimulator has detected an internal error. A factory reset clears most error states.

1. If this happens when plugging in the charger: disconnect the charger from the stimulator, then reconnect it — wall socket first, stimulator second. Charging requires the charger to be connected to the wall before the stimulator.
2. If the error occurs during normal use, perform a factory reset (see Section 3.13).

3.13 Factory reset procedure

1. Locate the factory reset button — it is inside a small hole just above the electrode connector on the side of the stimulator.
2. Insert a needle or pen tip and press the factory reset button for 3 seconds.
3. When the top three icons turn magenta, release the button.
4. After the reset, reconnect the stimulator to the Sooma App to re-download your session settings.
   • Error clears and device works normally → factory reset was successful.
   • Error persists after factory reset → contact Sooma to arrange a device replacement.

NOTE A factory reset clears all locally stored settings, including the loaded treatment protocol. The user must reconnect to the Sooma App to re-download their treatment plan before the device can be used again.

4. Sooma Support contacts for additional troubleshooting

If this Sooma DUO troubleshooting guide has not resolved your issue, contact Sooma directly. When reaching out, please have the following ready: your stimulator serial number (shown in the Sooma App under Profile), a description of the problem, and the steps you have already tried.