Though I believe the unit is overall in working condition, I cannot say with certainty that anything outside the scope of the description below is functioning properly. Some light wear to the chassis - mostly just a few scratches to the blue parts of the faceplate - but otherwise in excellent physical condition. Bought untested from previous owner.
Can confirm that 1/4 inputs/outputs work without issue. Have not been able to test other I/O, but presumably work without issue. Display seems ever so slightly dimmer when directly comparing to my second 550, but the difference seems completely negligible.In any case, brightness setting can compensate for any perceived loss in brightness. The Edit encoder knobs tend to skip when turning without any consistency. Parameters will jump around when turning.
From what I've read this is typical with these rack units as they age. May be able to fix with some Deoxit. Diagnostic mode tests passed for everything expect the encoder knobs and MIDI, as I do not have any MIDI devices with which to run the test properly. The item "Lexicon MPX 550 Guitar Reverb/Multi-Effects Rack Dual Channel Processor" is in sale since Saturday, June 26, 2021.
This item is in the category "Musical Instruments & Gear\Pro Audio Equipment\Signal Processors/Rack Effects". The seller is "andysseveredhead" and is located in Langhorne, Pennsylvania. This item can be shipped to United States.