harbach-electronics ss-100 User Manual

1

D1

1N4005 (1A 600 PIV)

K1 & K2

SPDT 12A 48VDC

R1 & R2

20

Ω

 10W

(240VAC)
R1 & R2

10

Ω

 10W

(120 VAC)
R3

2400

Ω

 2W 5%

C1 & C2

100

µ

F 63VDC

(1) SS-100 “S oft S tart” Circuit Board  Assembly

It is not p ossible to give exact installation instruc tions for the Universal “Soft Start” module because I

ha ve neither the schematic nor the physical layout of your specific am plifier.  I can give you enough
information, together with the schematic of the Universal “Soft Start”, to help you install this module.

Plea se exam ine the SS-100 m od ul e.  N ote that there are letters on the foil side that designate the

leads to be connected.  The “C” and “D” lead s will be co nn ec ted to the sw itche d power inpu t.  The  “A” and
“B” leads will be connected to the load.  A RED  wire betwe en p ads “C” and “D” (user supplied) is connected
to the neutral or return of the input power line.  Refer to the schematic below.  The m odule will be mounted
using silicone a dhe sive rel ay side to the ch assis.

The  overall o pe ration is qu ite sim ple.  W he n the power switch  in turn ed  ON , 240 volts is ap plied to

the load through a 20

Ω

 10W resistor in each side of the line.  The voltage at the load is measured by the

diode connected to pad “A”.  As the filter capacitors and other components charge or stabilize in current
drain, the voltage at pad “A” rises.  When this voltage reaches app roximately 90 volts, the two relays are
activated, shorting out the 20

Ω

 resis tors.  Now the power c ircuit is back to its full power state and the soft

start circuit is locked out of operation.

If this circuit is to be installed in equipm ent operating from 120-volt AC power lines, a mo dification

m ust be made.  The 20

Ω

 10W resistors must be changed to 10

Ω

 10W .  These resistors are readily available

at any electronic store.  However, if the soft start is used with equipm ent running on less than 120 volts, the
resistors probably do not need to be changed.

Jeff Weinberg – W8CQ

468 County Road 620

Polk, OH  44866-9711

(419) 945-2359