Sony subwoofer won't turn on: work through this
First, know what "on" looks like: a Sony sub with a red LED is powered — it's in standby waiting for the soundbar. Truly dead means no LED at all. The two problems have different fixes, so check the light before anything else.
Power diagnosis
No LED: press the sub's own power button first
Sony subs have a ⏻ power button on the rear panel — press it; the unit may simply have been switched off. Also note the LED's brightness follows the soundbar's DIMMER setting, so a dimmed LED can look dead. Neither of those? Continue.
Still no LED: prove the outlet and cable
Plug the sub into a different outlet on a different wall (not just a different socket on the same strip), and reseat the power cable firmly at the subwoofer end. Lamp-test the original outlet. No LED on a known-good outlet ends the DIY path — internal power supply failure.
Red LED: turn the soundbar on
Red standby is normal when the bar is off. Power the bar on and watch the sub — it should go green (or blink green, then solid) within 30 seconds.
Stays red with the bar on: 60-second reset
Unplug both units for a full minute. Then use Sony's documented order: power the soundbar on first, and connect the subwoofer's power after — watch for the LED to go green. This clears the majority of stuck-standby cases.
Still red: re-link manually
The unit is powered but the link is lost — run the manual linking procedure from the pairing guide.
Read amber and blinking-red correctly
On the SA-SW3/SW5, amber means a firmware update — Sony warns not to interrupt it, so leave everything powered until it finishes. On HT-S350/S400/G700 subs, solid amber is simply the normal linked state after Secure Link pairing — nothing to wait for. A blinking red LED is a protection warning: switch the sub off and check its ventilation openings aren't blocked before restarting.
Frequently asked questions
Is it normal for a Sony subwoofer light to be red?
Yes — red is standby, shown whenever the soundbar is off or the link is down. It's only a fault if the LED stays red while the soundbar is on and playing, in which case re-link.
My Sony sub turns itself off. Is that a fault?
Sony subs follow the soundbar into standby to save power — that's by design. Going into standby during playback, however, indicates link dropout: treat it as an interference/distance problem.
Can I replace the fuse in a Sony subwoofer myself?
There's no user-serviceable fuse on these units, and opening the cabinet exposes mains-voltage components and voids the warranty. A dead power supply is a service-centre job — get a quote and compare it honestly against replacement cost.