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Questions relating to designing PCBs
You really aren't giving us anything to go on...

What power amplifier board (part number, schematic, etc)?
What is the LED connected to? How? Is there any current limiting? What kind of LED?
Are you saying that some voltage should be 17V but you are measuring 17-23V? Where does this come from? What is powering it? Again - schematics!

My guess, given the little you give is, is that you are trying to run a standard LED on 17V, likely without a series current limiting resistor or other circuit. Look up "LED resistor calculator" on Google for more info on why it is needed and how to choose a resistor.

Also, this is likely the wrong forum for this question. This forum is for help in designing your own PCB (schematic capture, CAD, routing, etc.) The general forum is probably a better place.