HELP resurrecting a dead SB3

Hi All

After many years of faithful service, one of my two SB3s has died.

At first I thought it was simply the wall adaptor, but after swapping it with the one from the other working SB3, that is not the case.

I've looked at the thisthis post and found the following healthy looking voltages all measured relative to the ground pin of the barrel connector socket, with the WiFi card removed (which didn't fix it btw):
5.04 V
3.31 V
1.207 V
14.55 V
56.6 V
and with the WiFi card replaced:
5.02 V
3.31 V
1.209 V
14.55 V
56.6 V

The corresponding Ethernet 100Mbps link LED illuminates on my switch when the device is powered, but there's no sign of it on the network. Also, the red Toslink output can be seen, albeit very faintly. The voltage measured at the middle pin of the Toslink connector is 3.31 V.

When the unit died, I was listening to music from it (connection via the analogue outputs) and there was a distinct "crack" sound when the unit stopped.

Any help with suggestions on a possible fix would be most appreciated. It's so sad that these excellent devices were discontinued.