Before you open up the FS pre, make sure to drain the capacitors in the power supplies by depressing the buttons for that specific purpose.
Mr. Go is now in Brooklyn and, if open, will gladly help you with this repair, personally I wouldn't send my FS pre to anyone else - likely he'll 'fix' anything else inside the unit once he has it open. I've sent mine to him twice for upgrades and each time the cost was very much worth it.