Yamaha Clavinova CVP-8 power supply fault fixed!

My (previously parents') Yamaha Clavinova CVP-8 must be 25 years old now.  It had been getting into the habit of cutting out after it'd been on a while:  all the lights would go off and the buttons would be unresponsive, there'd be no sound from the keys but a gentle background buzz from the speakers.
If you turned it off and on again immediately then you'd get a gentle pop and all the same non-working symptoms, but if you left it off for a bit it tended to start working again, presumably as it cooled down.  However after a while it stopped the "starting working" again and was basically broken.

[Make sure you know how to be safe with mains electronics before you go doing this - there are dangerous voltages inside.]
Opening up the lid was a case of four screws on the underside, but the two at the rear are inaccessible while it's properly mounted on the stand just to make things more difficult.
Anyway, I'd found the power supply board with the big capacitors on it and I'd replaced those because I know that caps are often the thing that go bad in old electronics.  Unfortunately, this made no difference (though the piano did briefly start working again just to throw me off the scent).  FYI: The big cap in the bottom right of the board was charged to 20v and retained that voltage for at least a couple of days - nice big spark when I shorted it (so use a resistor)!

However, after another session of fiddling and some lucky turning on and off of the piano I worked out that my issue seemed to be that when it was working the machine had 2v or 4v (I think it was AC) measurable at (both sides of) the fuse towards the rear (using the metal heatsink case of that board as ground), and when it wasn't working it had 0v.    I traced the track on the underside of the PCB back to one of the end pins of the connector on the RHS of board - this was a wire directly from the big transformer, so I figured either the transformer was broken or... did that solder joint look slightly less than perfect through a magnifying class?  Turned out it was!  I resoldered all the joints on the bottom of the (what was it, 7 or 8 pin) connector and my Clavinova is working again!

PS  Credit to Yamaha for building a piece of kit that lasts this long.

(Other notes:  The rectifier near the connector gives out about 20v on the rear-right and the front-left pins.  I measure the cap of the (now replaced) big capacitor at the bottom right of the board and it was at 20v while the machine was on.  However,  the identical big cap next to it (by its "cap") was at 0v - not sure what that's about.  Off to the left two of the other 3 or 4 bigger caps were at 8v and 6v and the other two were 0v, I think.)