Modify Astron Pwr Supply to Charge Batteries Following are instructions to modify an Astron Power Supply to charge batteries being used to run radio gear and provide additional power to the batteries when current draws are high. This modification allows a battery to be floated on the Astron power supplies for battery back up while protecting the regulator chip from damage when AC Power is removed. It essentially adds a current limiting resistor in line with the voltage feed back of the regulator chip.
Installation is straight forward.
Cut the trace on the PCB between Pin 4 of IC UA723 and the wiper of R5. Set the output voltage by adjusting R5 to desired voltage with no load or battery connected to the power supply. 2 - For sealed gel cell batteries, set voltage to 13.8 vdc. Use of standard car batteries are not recommended. This will protect your system in the event that the power supply's crowbar circuit fires and tries to pull the current of the battery to ground.