Squeezebox Touch Power Supply Problem or a tale of 2 PSUs

[Richard]

Hi all, I recently bought another SBT second-hand to use with the vintage system in the other room. It arrived in good condition with SBT unit, original infra red remote and correct power supply unit.

It worked fine in the system using the phone app, but the infra red remote didn't work with it, nor did my old remote which is fine with my old SBT. However, both new and old remotes worked with my other SBT, so probably not a faulty remote.

Then swapped the power supply from the old SBT to this new one and magically now both remotes and everything else works fine on the new one!

Now of course the focus fell on a failing PSU working well enough to power the SBT but for some reason not the remote control circuitry.

I cleaned the plug connector but no joy so using a multimeter I checked DC out of both PSU units and both were 5.1VDC. Switched the meter to ACmV and the good one shows 0.1mVAC but the bad one 82mVAC - nearly a thousand times worse - but - bear in mind this is with almost completely unloaded supplies. They are 3A rating and I haven't checked them loaded but am in no doubt the new one has failed and ripple under load will probably be horrendous.

They made SBT from 2009 to 2012 and the newest will be 6 or 7 years old. So I didn't even think about chasing around for an old original PSU. I've ordered a new supply from RS and will let you know how it checks with the meter and if it works with the remote and all...

This makes me wonder about building a linear supply. Can anyone point me to a design or have any exp of whether a linear supply would be better than a SMPS in this application?