User Guide

1
PARTS LIST
D1 1N4005 (1A 600 PIV)
K1 & K2 SPDT 12A 48VDC
R1 & R2 20Ω 10W
(240VAC)
R1 & R2 10Ω 10W
(120 VAC)
R3 2400Ω 2W 5%
C1 & C2 100µF 63VDC
SS-100 UNIVERSAL “SOFT START” INSTALLATION INSTRUCTIONS
PARTS SUPPLIED WITH THIS KIT:
(1) SS-100 “Soft Start” Circuit Board Assembly
It is not possible to give exact installation instructions for the Universal “Soft Start” module because I
have neither the schematic nor the physical layout of your specific amplifier. I can give you enough
information, together with the schematic of the Universal “Soft Start”, to help you install this module.
Please examine the SS-100 m odule. Note that there are letters on the foil side that designate the
leads to be connected. The “C” and “D” leads will be connected to the switched power input. The “A” and
“B” leads will be connected to the load. A RED wire between pads “C” and “D” (user supplied) is connected
to the neutral or return of the input power line. Refer to the schematic below. The module will be mounted
using silicone adhesive relay side to the chassis.
The overall operation is quite simple. When the power switch in turned ON, 240 volts is applied to
the load through a 20Ω 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 approximately 90 volts, the two relays are
activated, shorting out the 20Ω resistors. Now the power circuit is back to its full power state and the soft
start circuit is locked out of operation.
120-VOLT OPERATION
If this circuit is to be installed in equipment operating from 120-volt AC power lines, a modification
must be made. The 20Ω 10W resistors must be changed to 10Ω 10W. These resistors are readily available
at any electronic store. However, if the soft start is used with equipment running on less than 120 volts, the
resistors probably do not need to be changed.
NOTE: If only one side of the input power line is switched, be sure that the switched lead is
on the “C to A” side of the soft start circuit.
HARBACH ELECTRONICS
Jeff Weinberg – W8CQ
468 County Road 620
Polk, OH 44866-9711
[phone]
http://www.harbachelectronics.com
[e-mail]