Direct answer
For the Sony X900H 4K TV, tV radio versus router band/security/signal and provider service should be separated. First, test another device on the same Wi-Fi and the TV near the router.
What this covers
- Sony X900H 4K TV (XBR-55/65/75/85X900H)
- Sony BRAVIA TV; Google TV/Android TV version, XR processor, panel and HDMI 2.1 ports vary.
- The specific fault this record addresses: will not connect to Wi-Fi or keeps disconnecting
What it does not cover
- ×The same symptom on a different Sony product line, which has its own record and its own cited source
- ×An on-screen error code whose meaning has not been checked against this exact model's manual
- ×Live electrical, gas, sealed-system, internal battery-cell or structural repair — a technician boundary, not a self-service step
Differential
What actually causes this, and how to tell them apart
These are ordered by how often each one is the answer, not by how easy it is to try. The point of the middle column is that two causes producing the same headline symptom rarely produce the same detail — that detail is what tells you which one you have before you change anything.
- 1
The signal at the set is marginal
What separates it Streaming buffers or drops after a period, while a phone held in the same room shows good signal.
How to confirm Check the set's own signal-strength indicator rather than trusting a phone. The TV's antenna is behind the panel and is frequently pressed against a wall.
- 2
The set is on a congested 2.4 GHz band
What separates it Slow or unstable streaming in an area with many neighbouring networks, on a set that supports 5 GHz but connected to the 2.4 GHz network.
How to confirm Connect explicitly to the 5 GHz network where the set supports it and is close enough to the router.
- 3
A router change was never applied to the set
What separates it The set stopped connecting after a new router, or after a password change.
How to confirm Televisions do not prompt to reconnect; they simply fail. Forget the network on the set and rejoin it.
- 4
The network requires a browser sign-in
What separates it The set joins but has no internet, on a hotel, campus or guest network.
How to confirm A television generally cannot complete a captive-portal sign-in page, so such a network is unusable without registering the set's MAC address with the network operator.
- 5
DNS or an ISP-level problem is being read as a Wi-Fi fault
What separates it The set reports being connected but apps fail to load, while other devices work.
How to confirm Test another device on the same network. A set that shows connected with failing apps is not a radio problem.
- 6
A wired connection is available and would be more reliable
What separates it Persistent marginal Wi-Fi on a set within reach of a router or a powerline adapter.
How to confirm Most televisions have an Ethernet port, and for a device that never moves this removes the whole class of problem rather than working around it.
Before you touch a setting
Record this first — changing settings destroys the evidence
Every item below stops existing the moment a reset, re-pair or settings change is made. Written down first, they are what separates the causes above; recovered afterwards, they are guesswork.
- The signal strength reported by the television itself, not by a phone held nearby.
- Which band the set is connected to, and whether the set supports 5 GHz.
- Whether other devices on the same network are working normally.
- Whether the router, its password, or the network name changed recently.
Read the signal strength on the television's own network screen
ReversibleThe set's antenna sits behind the panel, often against a wall, so its reception is frequently much worse than a phone suggests.
Forget the network on the set and rejoin it
ReversibleThis resolves most cases where a router or password changed, since a television never prompts to reconnect.
Connect to the 5 GHz network if the set supports it and is close enough
Reversible2.4 GHz is heavily congested in most neighbourhoods.
Test another device on the same network
ReversibleApps failing while the set reports connected is not a Wi-Fi problem.
Use the Ethernet port where one is available
ReversibleFor a device that never moves, a wired connection eliminates this whole class of problem rather than working around it.
Model-specific
What is true of this model and not of its siblings
Generic advice for the product line fails here. Each item below is a property of this specific model family that changes which of the steps above apply to you.
- Model scope
- XBR-55/65/75/85X900H. Sony BRAVIA TV; Google TV/Android TV version, XR processor, panel and HDMI 2.1 ports vary.
- Panel — full-array LED LCD
- 2020 full-array local-dimming LED LCD with the X1 Ultimate processor. A backlight with limited zones, so raised dark-room blacks and blooming are normal for the tier, not a fault.
- Smart platform — Android TV (older)
- This is the oldest Sony here and runs Android TV, the platform before Google TV. Update at Settings › Device Preferences › About › System update. On a 2020 Android TV, an app that stops working is often the provider ending support for that OS version — check the Play Store for an update before assuming a fault; a cheap external streamer restores anything withdrawn.
- Gaming / HDMI — 4K120 and VRR added by firmware
- Two HDMI 2.1 ports for 4K 120 Hz. Both 4K 120 Hz and VRR were enabled by later firmware updates — if they are missing, update the TV first (this set shipped before those features were switched on).
- Dolby Vision — yes
- Supports Dolby Vision, HDR10 and HLG — unlike Samsung.
- Symptom boundary
- This record covers Sony X900H 4K TV when it will not connect to Wi-Fi or keeps disconnecting. A different symptom on the same hardware, or this symptom on a different Sony product line, has its own record with its own causes and its own cited source.
Stop boundary
When this stops being a self-service repair
Continuing past any one of these costs more than the repair saves — in safety, in warranty, or in evidence a technician needs.
- !Do not weaken router security or disable encryption to get a television connected.
Evidence ledger
Sources behind this answer
Visible sources support the visible claims. Home Product Support records the publisher, the fact used and the review date; community reports can suggest an issue but do not become a published fact on their own.
Where the manufacturer's article stops. Sony Support publishes this as "Television and computer support". Official Sony and BRAVIA manuals, firmware and troubleshooting support. What that article does not carry is the model boundary — it is written for a product line, and XBR-55/65/75/85X900H is the scope applied here. Where a control label, terminal, indicator pattern or reset sequence differs on your unit, the manual for that exact model is the authority, not this page and not the article.
Exact questions
Common follow-ups
My Sony X900H won't do 4K 120Hz or VRR.+
The X900H shipped in 2020 before those features were enabled and received them through firmware updates, so update the TV first: Settings › Device Preferences › About › System update. After updating, turn on the enhanced HDMI format for the port your console is in and enable VRR in the source. Both live on the two HDMI 2.1 ports; the older HDMI 2.0 ports cannot do them.
My phone gets full signal right next to the TV but the TV keeps dropping.+
That comparison is misleading. The television's antenna sits behind the panel, usually pressed against a wall or recessed in a cabinet, while your phone is held in open air. Check the signal strength on the set's own network screen instead — it is frequently far lower. If the set has an Ethernet port and the router is reachable, wiring it eliminates the problem entirely rather than working around it.
Does this answer apply to every Sony model?+
No. It is scoped to XBR-55/65/75/85X900H. Sony BRAVIA TV; Google TV/Android TV version, XR processor, panel and HDMI 2.1 ports vary.
What should I record before troubleshooting Wi-Fi or disconnecting?+
Record the complete model identifier, exact message or indicator, software/firmware where visible, the operating stage and what still works.
Why is a factory reset not the first step?+
A reset can erase accounts, networks, maps, schedules or preferences without distinguishing Wi-Fi, disconnecting. The ordered checks preserve that evidence.
When should I stop and use qualified service?+
Do not weaken router security or expose network credentials.
Answer for the exact device and software version shown above.