Simplex 4020 Troubleshooting Manual page 22

Problems Associated with Assembly / Dis-Assembly and Installation,
Continued
Damage to Standard Slave
Protective Resistors
Flash Chip and RS232
Damage due to Improper
Orientation of Master
Controller U8 chip
Multiple ground faults and mis-application of the Audible/Visible jumpers can
destroy the 10 ohm protective resistors (R35, R63, R70 and R77) on the
Standard Slave PCB assembly.
The A/V jumpers interconnect A/V appliance horn & strobe power
connections H+ to S+ and H– to S– for applications requiring
simultaneous horn/strobe operation.
If multiple ground faults exist or when field wiring is set up for separate A/V
horn and strobe circuits without A/V jumpers removed, 24 volts will be placed
directly across the 10 ohm,
alarm condition occurs.
Note: Care must be exercised for systems being configured for
Audible/Visible appliance horn and strobe operation on separate
signaling circuits.
Remove any direct shorts between circuits, multiple ground
faults and all A/V appliance power jumpers.
If these interconnections are not removed, damage to the 10 ohm
resistors occurs the first time that the alarm is sounded.
In addition to electrostatic discharge (ESD), Master Controller PCB assembly
failures result from improper orientation of the U8 flash chip (refer to Figure
2-2, page 2-5). Proper orientation of this chip and download cable is required
to prevent flash chip and RS232 interface damage.
3-5
¼
W supervisory circuit resistors when the first