Thank you for your good
advice. Long story short, I sent my chart plotter back to Standard Horizon for
repair but was advise the mother board was hooped and that the cost of
repair would exceed the value of the unit. They advised me to
purchase a new chart plotter from a different manufacturer as Standard Horizon has not manufactured chart plotters for the past 5 years. So I purchased the voltage reducer as you suggested from Amazon. That did not
work out because it overheated and was a fire risk. So I returned it and purchased a "same but different" unit for $25. A much bulkier unit and simpler, it just puts out a 12 V
current from up to a 24 v supply. Non adjustable, just a steady 12 v. That worked like a charm and my chart plotter is back up and running. So, thank you for putting the idea of a voltage reducer out. I had never heard of such a thing before and your suggestion saved me hundreds of dollars.