I'm amazed at how helpful everyone has been so decided to give something back...
My once amazing Soundbridge Radio died after a year and two months (do they do that on purpose so it's just outside of warranty?).
Took it to bits carefully following the helpful instructions. SUre enough, inside the PSU the 220uF cap and the schottkey had frazzled.
Now I work in the electronics industry, and whilst the PSU looks a bit heath robinson, it's the thermal design of the unit that shocks me most. Electrolytic caps are renowned for having poor life (which drops off very quickly at higher temps) and the fact that the PSU is in a sealed box, which contains a virtually sealed plastic in which the PSU is glued is v. bad. The PSU didn't stand a chance long term so I'm not surprised at these failures.
Also, I can confirm ~450mA constant draw from the 9.5V rail regardless of whether the unit is on or off. This alone is over drawing compared with the PSU rating.
Since the design is fundamentally flawed, I did the following:-
- Removed the PSU (taking care not to damage the class D amp PCB for the sub)
- Removed the mains inlet, (scalpel and flat blade screwdriver)
- Snipped the four wires from output of the PSU (0, +9.5, 0, +19.5)
- Stuck the wires out the back through the mains inlet hole
Free of the PSU, I tried connecting a switched mode PSU (1 amp 9v) I bought from ebay to 0v, black (either is fine) and red, which is the 9.5v supply.
Soundbridge booted up fine! So was definitely the PSU that failed.
Just out of interest, I also connected the blue amp supply to +9V also and the whole thing works fine. Obviously the amplifier stages are happy running at a lower voltage.
Volume seems excellent still (at least in my kitchen) and all works perfectly - couldn't hear any degradation in sound quality from the lower voltage. I actually ordered a 19v cheap laptop supply for the amp circuit but to be honest, I think I'll just run the whole lot from 9v as it does me fine.
So don't fret if you don't fancy mending the PSU - remove it and bin it and wire up a 9V regulated 1 amp adapter and your radio will live again!
Thanks all again.