In case you haven't found it:

Parent page for:

Fender Champ 5C-1 schematic

and:

Fender Champ 5C-1 layout

If this is the right model, the tubes are:

6SJ7, 6V6-GT, 5Y3-GT (from the layout - The schematic omits both "-GT" bits)

A 5Y3-G that's probably an "early -GT" is shown as obsolete/discontinued (in 1960) but the successor 5Y3-GT was still good "back then."

Note: Both diagrams show a 2A fuse - surely you checked it first?

The layout shows some other component values, if you don't have something better for reference.

John