After similar experience, I disassembled my base unit and discovered a melt down of a capacitor on the main PC board. This is the message I sent to Bose:
Hi, Prior requests for support have not let me to a fix. Spare time has led me to try to repair my BOSE Unit myself. Disassembly reveals that I have a failed Nichicon capacitor, labelled 15000 µF, 25V, 22mm dia, 45 mm height & marked VZ(M) 105°C, in the main PC board. Photos are attached. It leaked a white sticky, pasty goo, apparently from the end opposite the pins, and appears melted to an amber colored resinous solid at the base. A 2nd similarly labeled capacitor in the unit, in the sub-board that attaches to the power, speaker & control unit, shows no similar leakage of white goo or resinous colored solid/ deformation at the base.
Using the finder at https://www.mouser.com/Passive-Component... which lead me to https://www.mouser.com/ProductDetail/Nic... , I think it is Mfr. #: UKT1E153MRD, Mfr.:Nichicon. I hope you will confirm the specification so I can order a new one and install it. I can solder, and it appears to be a straightforward replacement of a $6.23 part- what do I have to loose?
In exchange for your assistance, I free and release Bose from all liability.
The unit is a BOSE 321 series base module 321 GS Series II, bought at the Bose store in Manchester VT 12/28/2005, Customer serial # 03566695715622AZ, S/N 034200950062395AY.
So far, no help from Bose. I'm searching for the replacement capacitor, will install it and see what happens…