Marshall-1974X-18W-Schematic.pdf
you're quite a bit off! here's the 2004 version of the 1974X schematic for you to study and see where your mistakes are i.e. you can't have both the 120V & 240V pirimary wires going to the switch,the red/yellow HT centre tap goes to ground via the HT fuse,the 2 red HT wires go to pins 1&7 of the ez81,the yellow/black wire is rectifier filament 5V and is not used etc,etc
note someone has been in there and changed the 91R bias resistor to 200R.
see if you can work out the wiring also do the mounting bolts of the 290 paz match your existing holes?
good luck
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