Be aware that the "fusistors" on the driver board don't tend to fail outright, they drift off the original spec over time, which usually trips the protection circuit.
I'm not saying they're not your particular unit's fault, but bad "fusistors" on the F-2624 driver board doesn't seem consistent with the symptoms that you've described. Could be, but doesn't sound right to me.
But it also wouldn't be the first time a Sansui 8080DB/9090DB receiver has made me go: "what"?
Both channels out at the same time tends to point me to something that's common to both.
That would normally be fuses or the speaker relay contacts.
But you've metered the fuses. You did at least lift one side of the fuse, yes?
Maybe take the bottom off and see what the contacts look like in the protection/speaker relay. My relay has a clear case and you can get a decent look at the contacts without taking the relay apart.
I can't remember if you have to remove the tone board to see the relay, but you do have to take it out if you plan to clean the contacts. If they're black and pitted you may have found the issue. Don't sand the contacts, burnish them. They're silver plated and you just want to clean them, not strip the silver plating off them.
I usually cut a small strip of a non-shiny business card that will fit between the contacts, put a couple drops of deoxit on it, slip it between the contacts and rub it back and forth. I keep repeating that with fresh strips until the paper comes out clean.
I don't think that a dirty relay killing the signal would also make the VU meters go dead, but I could be wrong on that...
So you now know to replace every fusible no matter what. I put 1A fuses in their place wired to remote fuse holders. So if they blow, then simply pop in new fuses without surgery.
