Problems Associated With Assembly/Dis-Assembly And Installation - Simplex 4020 Troubleshooting Manual

Problems Associated with Assembly / Dis-Assembly and Installation
LCD Annunciator Short
Circuit
LCD Annunciator Cable
Chafing
Mapnet Damage due to
Physical Stress on Power I/O
Interface PCB
Improper Orientation of
Standard Slave–to–Power I/O
Interface Connection
Some back boxes have a conduit fitting mounted in the upper right-hand corner
where it is possible to contact the rear of the P3 connector of the LCD
Annunciator CPU Memory assembly (Part No. 565-078).
If the LCD Annunciator assembly is removed with power on, it is possible to
momentarily short the 24 volt power to the 5 volt circuitry by contacting the
conduit fitting.
It is also possible to short interconnections between circuit boards by contacting
the inner flange of the one-piece back box.
Chafing can occur between the back box and the membrane panel cable.
In severe cases, cables may open circuit and prevent proper annunciator or
keypad scan operation. Return lines may be intermittently shorted together
thereby creating intermittent key depression chips.
Ground faults can result from cable chafing. It has been reported that ground
faults can also induce this so-called "chipping phenomena".
A high percentage of 565-256 Power I/O Interface PCB assemblies have
exhibited capacitor C12 damage. This can be due to physical stress applied to
the capacitor leads during PCB handling or removal of the 636-341 Universal
Power Supply assembly. The Power Supply must be rotated during removal and
can easily stress the C12 capacitor located near the PCB corner. This may cause
subsequent Mapnet interface damage when the system is turned on
Once damaged, movement of capacitor C12 can cause intermittent variation
from its rated 330uf capacitance to less than 50nf. This lack of capacitance
damages the Power I/O Board Mapnet +36V regulator and Standard Slave
Mapnet Interface components.
This problem has only been observed on assemblies with the blue jacketed C12
Sprague capacitor. If it is suspected that this capacitor may have been damaged,
the 36VDC Mapnet voltage should be measured while gently moving the C12
capacitor.
Note: If the Mapnet voltage is significantly less than or greater than
36VDC do not install a new Standard Slave PCB assembly until
the Power I/O Interface PCB has been replaced.
Care must be taken to properly orient the 20-conductor ribbon cable that
interconnects Standard Slave connector P9 to Power I/O Interface connector J1.
These sub-assembly connectors are staggered slightly and
orientation keys to insure proper connection.
Continuous sounding of the piezo horn and clicking of relays may indicate
connector mis-orientation.
Proper Power Supply cable connection to the P9 Power I/O Interface connector
is essential for +5V system power regulation and system initialization.
3-4
have
DO NOT
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