[Radio Wrangler]

I'm not convinced that was the main switch you removed, Michael.

The two orange capacitors right by the main transformer look like the capacitor pair of a half-bridge, and the two larger semiconductors under them... with their centre pins chopped look like the the pair of power MOSFETs of a half-bridge The pins in sight are gate and source. The drain is connected via the heatsink tab soldered to the board. Chopping the drain tab short is a common trick because the SMT pad pattern for the board for that package is a bit low on creepage distance for the voltages involved.

To the left of the transformer is a 1n0 capacitor and a 6-pin semiconductor. I guess the latter is an opto-isolator as the regulation feedback path across the high voltage isolation cordon, and the 1n0 is an RFI capacitor also across the cordon. The output rectifiers and filters are crammed hard into the bottom part of the board, below the cordon.

Its general appearance is that this board has been run hard and hot for a long time.

The next thing to do is to identify the two control chips. I guess the lower right one is a half-bridge gate driver. The two large-ish SMT ceramic capacitors would fit with this idea, though plenty of SMPS control ICs have the drivers buil in, but still need the capacitors. So if the right hand chip includes the controller, then what is the left-hand chip?

The two Schaffner lumps are common-mode anti-RFI chokes. The orange gumdrop at top right may be a metal oxide varistor to protect against surges, the black cylindrical thing below it may be a thermistor to control inrush current at turn-on The two connectors on the top are at a guess L and N inputs on one and maybe a voltage range switch on the other?

THe part you removed, below the reservoirs has its centre leg joggled out of line with the other two. This is another trick to increase creepage distances for high voltage parts. Could this be that ST high voltage regulator chip?

If so, then it may be the startup supply. The other bits around it may be the main supply for the control circuits, derived from a winding on the main transformer.

The close proximity of the half bridge (orange) capacitors and the switch MOSFETs of the other arm of the half-bridge is a good way of minimising radiated field. The copper strap around the transformer will be soldered along its join, it is a shorted turn around the outside of the whole transformer, designed to stom flux leaked from the core.

This looks fairly followable and with the data for those two chips ought to be manageable.

The question comes down to cost and time to repair. On the other hand, these things seem to not exactly be blessed with wonderful reliability and there are people chasing spare units. That sounds like a recipe for a worthwhile market. If you get this one going, you will have learned enough to be able to fix others, and there seem to be plenty of others out there with people who want them fixed.

In my hifi system, there is a Sony XA5400ES CD player. Inside, it's well made with linear supplies and iron mains transformers (With R-type core shapes) Their marketing schtick is having separate mains transformers for analogue and digital sections in the hope that some people will think it makes a difference. But nice, low stress linear supplies might make up for in reliability what they lose in efficiency. Looking inside the Linn stuff, I don't see anything added which fits with the dramatically increased price.

David