Hi, been using a Sonos amp with no problems for about 2 years. Went to turn on today and heard a click then nothing. Out of warranty, and as an engineer stripped it down. Fuse ok, but I saw a chip had blown on the power board. U3, between R20 and c19. Could somebody let me know what and if this chip is available?
I have no idea about chips used in Sonos hardware as unlike you I’m not an engineer. However, Sonos does not have a repair service so therefore chips are not available on the open market.
On the other hand Sonos has been known to offer a replacement at a reduced cost. That however required a diagnostic to be sent to Sonos as verification of a defective unit. Since you have opened yours up you may have killed any chance of being offered a reduced price replacement. You might still call Sonos to get a definitive answer. Just be careful as to how much information you provide.
You might check to see if there are any YouTube teardown videos which might reveal the information you are seeking.
Thanks for your suggestion regarding the Sonos repair service 
if anybody has a picture of the offending chip with a part number visible that may also help me
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