Something I found  - Page 1
Forum section: electronics / beginners

author: NORange
author_rank: Contributor
timestamp: September 12, 2025, 02:11:19 am
content: From a broken speaker I extracted the power supply board and a controller board driving the 4ish speakers. It appears to support Wifi/Bluetooth, judging from the pcb inverted f antenna.

author: NORange
author_rank: Contributor
timestamp: September 12, 2025, 03:08:56 am
content: The attachment shows fiber(?) and USB 2 receptacle, DC jack, IR sensor, and a speaker.

author: Psi
author_rank: Super Contributor
timestamp: September 12, 2025, 03:28:17 am
content: There are home theater speakers that send the audio data wirelessly from the center speaker or sub.It helps because you only need to find power around your living room instead of running speaker wires everywhere for a 5.1/7.1 system.LTT did a review of one of them, might have been a soundbar actually, but yeah, it had wireless rear and side speakers.

author: golden_labels
author_rank: Super Contributor
timestamp: September 12, 2025, 04:15:09 am
content: But what is the question? Or what do you expect from us?The context makes me think that the device indeed has wireless connectivity of some sort. But in general you may find devices with partially or even fully populated communication circuits, despite not offering that. To the manufacturer it may be cheaper to just solder on an entire communication module daughterboard, even if only a single feature is used.The reasoning goes way beyond the cost of the physical piece of PCB and silicon.

author: radiolistener
author_rank: Super Contributor
timestamp: September 12, 2025, 05:00:58 am
content: Is it actually a Bluetooth speaker?By measuring the length of the antenna (excluding the feed line), you can roughly estimate the operating frequency — it will be approximately λ/4. For Bluetooth, this corresponds to about 30 mm. Based on the photo it is difficult to make an exact assessment, but the antenna appears to be designed for operation around 2.4 GHz. So, its probably Bluetooth or WiFi.

author: NORange
author_rank: Contributor
timestamp: September 18, 2025, 12:14:30 am
content: It's a Vizio 38 inch sound bar that has Bluetooth function.

author: NORange
author_rank: Contributor
timestamp: September 18, 2025, 12:26:16 am
content: This is more of a 'show-and-tell' post, but I do have a question. It seems that many PC, TV, and other consumer electronics use black PCB instead of green (irrc cheaper) ones, so why is it the case?

author: amyk
author_rank: Super Contributor
timestamp: September 18, 2025, 03:11:54 am
content: Solder mask colour isn't going to affect the price much anymore, unless you want a specific exotic colour. Green, blue, red, and black are all common and they probably just used whatever might've been the cheapest by a tiny amount.

author: Gyro
author_rank: Super Contributor
timestamp: September 18, 2025, 06:03:19 pm
content: Itmightmake the PCB marginally harder to reverse engineer from photos - but not enough to make a difference to any serious attempt. Itmightimprove the contrast for machine vision systems [or inspection] - but they don't have any difficulty with other colours. Itmightbe to make the component idents a bit clearer to see - but they wouldn't expect anybody to be repairing it at the component level. Itmightimprove the contrast of LEDs driven at low current - but I don't see any. So the answer is probably, because they liked it that way.Some of the above factors might be useful on some other boards though, eg. Protos.