You have a rare PL2000 Series II factory export wired for 220V. I don't think the folks at PL offered (or contemplated) the PL2000 Series I would ever be exported, so I don't think that they made the Series I for 220V.
That small transformer (T1) has a dual 120V/220V primary. Clearly, the cable is a three-wire and to be in compliance with most 240V countries, the earth (green) wire is securely connected to the chassis. You can buy a 120V to 240V step up transformer and keep your preamp original, or you could convert it back to USA specs. Just don't plug it in to 120V, it will not be happy. Based on the zip-tied cloth covered wiring, I would say it is still factory wired for 220V operation.
Pretty sure about this, but I would measure to be safe: One primary winding is Brown and Brown w/ Yellow stripe, the other primary winding is Blue and Blue w/ Yellow stripe. You have the Brown w/ Yellow stripe and Blue connected together and the one wire of the AC voltage going to Brown and the other wire of AC voltage going to Blue w/ Yellow stripe which places the windings in series for 220V operation. To convert it to 120V operation the primary windings need to be in parallel. When transformer primary windings are connected in parallel, the phase must be correctly observed or the transformer will become damaged. To do this properly, you would connect one wire of the AC to both Brown and Blue twisted together and the other AC wire to both Brown w/ Yellow stripe and Blue w/ Yellow stripe twisted together. This is a standard PL convention, I have wired PL700 Series II amplifiers for dual voltage operation and that is how it's done.
Personally, I would install a 'dual voltage' switch after the fuse and make the primary voltage selectable. You would need to drill two small 1/8" holes and a small 'window' to mount the switch inside the unit. I can send you the switch and the instructions how to wire it in, if you desire.
