Sonos Play 5 (1st generation): repair of a complex power supply fault

Sonos doesn't offer or support repairs and few users here do them. Maybe another forum?

OK. I’ve read on this forum that many users modify this speaker to use an external power supply, which is a good idea, but it’s not always necessary.
Greetings to the community

While I have no experience with PLAY:5 repair, in general I have noticed that adhesives often become conductive and should be removed. Adhesives are useful during fabrication and shipment, but they are not needed while the unit sits in place. A conductive adhesive may result in over current causing another component failure.  A conductive adhesive can also cause noise, possibly that 7-15V variation. I suggest that you remove any adhesive that appears discolored.

From your photo, its possible that there is an adhesive issue with that large capacitor and the overall PC board may need a cleaning.

Edit: That 7-15V variation could easily result in component damage. Be sure to check voltage regulators and Zener diodes.

The three resistors shown in the photo were faulty. After replacing them, the power supply started working, and 12 V and 24 V voltages appeared. This means that the feedback (FB) function in the integrated circuit began to work properly. In addition to cleaning, I suggest performing some basic measurements.