Subwoofer on Sony HT-CT290 sound bar not working

"Hi @tiffanylaw ,

There is nothing obvious showing in the pictures so it will come down to doing some tests, initially static testing (without the power connected) but after that it will need to be with the power connected.

If neither you or your son has any experience testing when exposed lethal voltages are present then don’t do it. It is not worth it

(click on image to enlarge for better viewing).

I’ve highlighted some points of interest in the image above where you may wish to check first.

With the power disconnected (green arrows) use an Ohmmeter:

check that the fuse on the ‘power’ board is OK i.e. short circuit measurement shown on Ohmmeter

can’t see it to well but if the regulator shown on the ‘amp’ board is a TPS54334 then these are prone to failure over time.

Not quite sure what you would measure when testing the regulator with an Ohmmeter in this particular circuit but you shouldn’t see a short circuit or an open circuit when testing across the pins. There are actually two regulators in the same package

If it is faulty and you cannot find a direct replacement a MP2307 is an equivalent component.

You will need smd (surface mounted device) soldering tools and skills to remove / replace the component

If it is determined from the static tests that the two check points suggested are both OK (green arrows) then you will have to connect the power and perform “live” testing. See note above re testing live circuits.

Again can’t see it too well and I haven’t got a schematic to work from but the red arrow points to what I think is the STBY (standby) power lead going from the power board to the amp board. This should be a DC voltage, its’ value is unknown to me, but given the regulator operates at anywhere between 4.75V DC to 28V DC you shouldn’t see any DC voltage higher than the 28V DC

Check if there is a DC voltage on the lead.

If there isn’t then there is a problem in the power board.

If there is then there is a problem on the amp board as the STBY power is to let the amp board “know” that power is available and it switches on the power light.

Be aware that there is exposed lethal voltages on the power board when you’re doing this.

Hopefully this is a start"

As mentioned by @jayeff, the TPS54334 regulator was the problem, however I don’t have the equipment to resolder since it turns out this chip also has a soldered thermal pad under the chip. I did happen to have an LM2596 DC-DC buck module (about $1.50 from amazon). I connected it to the 18v supply (soldered to pins 2 & 3 of CN8102 connector) and ground (thermal pads that were under the chip) and set the regulator output to 3.3v. Then I connected the output to the two large tabs (assuming test points) just above the chip (make sure to get polarity correct). No SMD soldering required. I used some heat glue to stabilize the board since there will be a lot of vibration from the woofer. Here is picture of the results - notice the blue module with LED where the chip used to be:

"Hi @steve_t

OK some info.

Here's a supplier for the 3.3V standby voltage regulator

Here’s a link for the 5V regulator EUP3482ADIR1. I don’t know where they are located, but they quote in GBP

Here’s the service manual for the sub woofer . Sorry about the link to the main unit service manual in my comment above.

This link is harder because you have to view it online and go from page to page by typing the page number in the box below the document page and then click go. To download it you need to sign up with the website.

The regulators are shown on p.15. It seems as though the 18V output from the power board supplies power to the regulator to produce STB_ 5V and presumably when the unit is turned on it becomes SYS_5V and the STB_5V also feeds to the regulator for the STB 3.3V

Check the outputs of the two regulators. The circuit shows the pins. Apologies if you know this etc

(click on image to enlarge for better viewing)"

"Hi @M Kuzma

Here’s the service manual

Haven’t had time to review it but but has the schematics so you should be able to work out how the power gets to the regulators on the mainboard to provide the different voltages and also what type of regulators they are. Once you know the regulator model number, search online for replacements using the model number of the component. Search on places such as mouser.com, digikey.com"

"@jjanishas

You may have been using the wrong information from this page

You have a different model than what the models on this page are all about. A Sony SA WCT-290 is different to a Sony HT CT-290

Here's a link to the service manual for your model.

Follow the appropriate flowcharts on p.11 or p.12 to see where that leads you."