[K3PZN-List] See forwarded message below...

[Keith Krichinsky]

GUYS,
    MAYBE THIS WOULD BE USEFUL FOR ANYONE WANTING TO SET UP THEIR BASE 
STATIONS TO BE ABLE TO OPERATE ON EMERGENCY POWER IF NEEDED!?
    MIGHT BE A GOOD MOD TO PUT IN THE NEWSLETTER ALSO??

                                DAN (N3EEI)
]


http://www.hamsrus.com/astronmod.html



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.  Source: Civil Air Patrol

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.   Install a 10K ohm 1/2 watt resistor to 
bridge the cut trace between Pin 4 and R5.  Set the output voltage by 
adjusting R5 to desired voltage with no load or battery connected to the 
power supply.

Voltage settings:
1 - For standard deep cycle marine batteries, set voltage to 13.5 vdc. ( Do 
not forget to periodically check water level in battery )
2 - For sealed gel cell batteries, set voltage to 13.8 vdc.

Use of standard car batteries are not recommended.

It is HIGHLY recommended that a fuse rated at equal to or less than the 
maximum current rating of the power supply be installed between the battery 
and the power supply.  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.

Recommended hook up should be:
1 - Hook equipment to the battery
2 - Hook battery to power supply

In this configuration your equipment is being powered by the battery and the 
power supply is serving two functions.  One is keeping the battery charged, 
and second to aid during high current draws. It will also allow the battery 
to act as a surge protector adding some additional protection to your 
equipment from line surges.

Thank you,

Keith Krichinsky, KB3HHK



_________________________________________________________________
Protect your PC - get McAfee.com VirusScan Online  
http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963