[TenTec] Re: Astron mod

[WILLIAM MANSEY]

Hi Mike and everyone,
    The modification is to protect the regulator from excessive current, in
the current limiter circuitry, due to the presence of the battery.  I
apologize for the poor quality of the schematic on my web page.  I do not
know what caused that because it WAS clear when initially viewed on my
computer.  At any rate - the modification is simply cutting a foil on the
circuit board between pin 4 of the 723 regulator and the wiper of the
current limit potentiometer and soldering in a 10k 1/2 watt resistor across
the cut.
    As far as Astron reliability is concerned - - - I have 2 RS-35's and a
RS-20 which have been on 24/7 for about 4 years (aside from the occasional
power failure OR when I turned one, or more, off briefly to do some wiring
changes)  I have had no failures or even hints of failures with these.  I
have experienced failures of power supplies (with 723 regulators) and in
each case the failure resulted in loss of drive and ZERO output voltage.  I
never had one run wide open due to a regulator failure.  A shorted pass
transistor WILL, however, cause such a failure.  BE sure to use a power
supply that has a "crowbar' circuit OR build such a circuit yourself!
    By the way; One of my Astron 35 amp supplies has front panel voltage and
current adjustment.  I set that to 13.8 volts at the battery.  The other
Astron 35 amp supply is not adjustable BUT I just checked the voltage across
its battery and it is also exactly 13.8 volts.   I hope this information is
helpful.  73, Bill