FAQ
TL;DR: When Somfy J4 WT façade blinds share a 230 V circuit, releasing the switch can cause about 1 s TV blackouts; "The screen goes black for a while." Fix by isolating power, filtering, or adding a snubber. [Elektroda, bhtom, post #17512664]
Why it matters: It prevents HDMI dropouts and equipment stress for homeowners and installers sharing TV and blind motors on one circuit.
Quick Facts
- Symptom snapshot: ~1 s video loss exactly when the blind switch is released; wiring was routed with mains in one wall trough. [Elektroda, bhtom, post #17512664]
- Isolation proof: plugging the TV into a different circuit via extension removed the blackout entirely. [Elektroda, MarekKubica, post #17516735]
- Motor context: Somfy J4 WT 10 Nm draws about 1 A at 230 V; the issue appears on button release, not at start. [Elektroda, MarekKubica, post #17516773]
- Field fix suggested: “Fit a power filter at the roller shutter” to cut conducted interference. [Elektroda, Zbigniew 400, #17516750]
- Alternative fix: “resistor and capacitor in series” across the switch contacts (RC snubber). [Elektroda, ditomek, post #17527502]
Why does my TV lose signal when I release the Somfy blind switch?
Opening the switch can produce a release transient on the shared 230 V line. That brief disturbance can upset sensitive TV power or HDMI links. Users address this by damping the release with an RC snubber across the switch contacts. “Resistor and capacitor in series” is the suggested remedy. This targets the exact moment you release the up/down button. It reduces the spike that coincides with the TV blackout. [Elektroda, ditomek, post #17527502]
How can I quickly test if the shared circuit is the culprit?
Do a fast isolation test.
- Plug the TV into an outlet on a different circuit using an extension.
- Operate the blind and release the switch as usual.
- If the blackout disappears, the shared circuit is coupling the disturbance.
This exact test removed the symptom in the thread. It strongly points to conducted interference on the original circuit. If confirmed, plan separation or filtering. [Elektroda, MarekKubica, post #17516735]
Why does it happen on release, not when the motor starts?
In this case, the disturbance appears only when the button is released. Startup produces no visible effect on the TV. That timing indicates the issue is linked to the switch opening event. The motor is about 1 A at 230 V, so steady load is modest. Focus mitigation on the release transient, not the inrush at start. [Elektroda, MarekKubica, post #17516773]
Do HDMI and mains run in the same trough cause dropouts?
They can correlate with dropouts. One installer saw all cables routed together in a wall trough. Switching room lights caused about a 1 s image loss on an older LG plasma. The screen went black briefly and then recovered. That shows proximity coupling can aggravate visible glitches. Separating signal and power paths is advisable during planning. [Elektroda, bhtom, post #17512664]
I separated HDMI and power but the TV still blanks—what next?
If separation does not help, isolate the supply. Power the TV from a different circuit and retest. In the thread, this eliminated the issue immediately. That confirms the blackout rides the original branch, not the HDMI path. Next steps include circuit separation or adding suppression at the blind side. [Elektroda, MarekKubica, post #17516735]
Could poor wiring or high inrush on the circuit cause this?
Yes. “This ranges from poor connections in the boxes to too much instantaneous consumption in a given circuit.” Loose terminations can amplify transients. High instantaneous load can deepen dips that some TVs dislike. Inspect terminations in junction boxes and the distribution connection. Fix any weak points before adding filters. [Elektroda, sosarek, post #17516741]
What simple fix can I try at the wall switch?
Add a snubber across the contacts. “Resistor and capacitor in series clipped onto the contacts of the roller shutter switch.” This RC network damps the release spike that coincides with the TV blackout. It is a common field remedy for switch-off transients. Use a mains-rated snubber module or RC pair. [Elektroda, ditomek, post #17527502]
Where should I place a power filter for best effect?
Place it at the blind side. “Fit a power filter at the roller shutter.” That location stops conducted noise from re-entering the branch. Use an enclosure suitable for the environment if installed near the window. Keep leads short for best attenuation. [Elektroda, Zbigniew 400, #17516750]
Could this blackout damage my TV or other devices?
The reported symptom was a brief image loss, with no lamp flicker on the same outlet. Powering the TV from a different circuit removed the blackout. That suggests a short disturbance rather than sustained undervoltage. To reduce risk, keep the TV on a separate branch or add suppression at the blinds. [Elektroda, MarekKubica, post #17516735]
How do I check whether the wall switch itself is at fault?
Swap the control key/switch with another unit to A/B test. “Check the key itself in that case—swap it with another one to try it out.” If the symptom follows the switch, replace it. If not, move on to filtering and wiring checks. [Elektroda, sosarek, post #17516782]
Does this only affect antenna TV reception?
No. The blackout also appeared while watching VOD over HDMI from a Blu‑ray player. There was no terrestrial TV in use. That indicates the issue is on the power side, not RF antenna paths. HDMI handshake can drop when the TV’s supply hiccups. [Elektroda, MarekKubica, post #17512535]
My circuit has multiple sockets—does that matter?
It can. The reported circuit had four different sockets on the branch via WAGO connectors and 3G2.5 cable. The Somfy J4 WT motor is about 1 A at 230 V. Despite modest current, the blackout still occurred on release. Circuit layout and contact release behavior mattered more than steady load. [Elektroda, MarekKubica, post #17516773]
Will switching to an electronic controller like Blebox Shutterbox help?
It may change switching behavior, so testing makes sense. Roller shutters controlled by Blebox Shutterbox worked fine in the same home. The plan was to try façade blinds with Shutterbox and compare. If the symptom disappears, keep that control path or add filtering. [Elektroda, MarekKubica, post #17512496]
What did Somfy support say about built‑in filtering?
Somfy stated these motors include internal electronics and filters. They advised checking the electrical installation for faults first. The next planned steps were Shutterbox control and ferrite filters for experimentation. Document results after each change for clarity. [Elektroda, MarekKubica, post #17529635]
