Rev. A.2, 10/03 |
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APPENDIX B: TROUBLESHOOTING
Note first that the
PROBLEM-- Unit appears dead.
First check that power has been correctly connected and use a voltmeter on the CPU board to make sure that the correct voltage level is present. If the voltage reads very low, the problem may be that a fail safe lock being controlled by the
If the
If the relay doesn’t operate when SRC and REX are connected, the CPU board has either tripped one of its automatic fuses or has some major problem requiring replacement. The
AC | PS3 PS2 PS1 |
IN |
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PolySwitch #1 comes into play only if you are powering the unit from an AC source connected to the AC input terminals. It protects against an internal short on the board in
the components (four large diodes) that convert AC to DC. If you are powering the board with DC voltage into the DC input terminals, you can ignore PolySwitch #1. PolySwitch #2 protects against an internal DC short circuit on the CPU board. PolySwitch #3 protects against a short circuit in the keypad which can be caused by skinned keypad wires or
To check the PolySwitches, apply the probes of a voltmeter to both PolySwitch leads. Note that you have to do this with power on the board. If you are checking PolySwitch #1, set your voltmeter to AC. Set it to DC for PolySwitches #2 and #3. In the normal condition, the PolySwitch will be conducting current so you will read less than one volt. A tripped PolySwitch acts as a high impedance resistor so you will read several volts across the PolySwitch leads. If none of the three PolySwitches have tripped but the properly powered board will not operate its relay when SRC and REX are briefly shorted together, the CPU board must be returned for replacement to the factory.
Any time you find a tripped PolySwitch, you have to understand how to reset it. Overload current through the PolySwitch trips it so that it clamps the current down to roughly 100 mA. The PolySwitch will continue to clamp until all power is removed for about 5 seconds. It is not enough to correct the overload condition; you have to depower the board for 5 seconds and the PolySwitch will reset itself.