I’ve spent some time reviewing the schematic. Looks like mine is the neater and easier to read version from the service manual: I’ve worked this out because mine has the lamp dimmer switch on the rear which on further inspection seems to feed another 2 lamps which are not on my unit. I suspect that’s what the cut green wire is from on the front panel as it’s the same feed as the green wire for the other lamps. You can see it here on the right of this amp. 2 bulbs and 2 plates to shield the rest of the front panel: This seems odd. I can’t understand what these bulbs are supposed to be doing, let alone why you’d need to dim them.