Is there a safe dc voltage range for sirius radio model st4?

Want to replace sirius car charger of 5v, 1.5 amp. Have 1.5 amp charger that gives range choices that include 4.5v, and 6v. Can they be safely used? Will 4.5 v not give enough power & blow fuses, or will 6v be too much & damage unit?
Asked Feb 02, 2014

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