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[AMPS] SB220 problems

To: <amps@contesting.com>
Subject: [AMPS] SB220 problems
From: w8ik@ibm.net (Joe Subich, W8IK)
Date: Sat, 26 Dec 1998 10:56:33 -0500


> 
> My SB220 contains a small transformer with two windings. One winding
> supplies the filament voltage for the 3-500zs and the other supplies
> bias and relay voltage at 120volts. One side of the relay coil is
> connected to this little half wave supply. The other side of the relay
> coil goes a jack on the back of the linear. When this jack is grounded
> it closes the relay and the linear goes into the transmit. From the
> banded end of the diode rectifier, a 20ufd, 160 volt electrolytic
> capacitor is connected from this point to ground. Without this
> capacitor  the relay will not close. It just chatters from the pulsating
> dc voltage. Just what you'd expect.
> 


Install a larger (voltage) capacitor or a series resistor (47 Ohm 2 watt)
ahead of the capacitor.  120 volts * 1.4 (for a capacitor input filter) 
is 168 volts on the capacitor ... it's too close for comfort particularly 
if the line voltage is a little high.  Also, make sure the polarity is 
correct on the capacitor! 

73,
   ... Joe Subich, W8IK/4  ex-AD8I
       <W8IK@IBM.NET>
 

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