Type B Vital Relays - Alstom

Troubleshooting
5.4.3. Microchron II Timer Relay Troubleshooting
Both the AC and DC versions of the Microchron II Timer Relay contain a red LED and a
green LED.
The Red LED indicator is the TIMING/POWER ON indicator. It is lit when power is first
applied. It will begin blinking OFF/ON at 1.0 second intervals until the delay set on the
switches has expired. On the AC Microchron II Timer Relay, the final blink will be slightly
quicker or longer depending on the tenth of second switch setting. Then the Red LED
illuminates steady when the timing cycle is complete and power remains supplied.
The Green LED indicator is the DELAY COMPLETE indicator. It is lit at the end of a
delay. Once the delay has expired, the power that is driven through the Vital Relay
Driver (VRD) tuned circuit to the vital relay also drives the Green LED to indicate the
end of the delay.
NOTE
If the Microchron II Timer Relay completes its time cycle and the green
LED illuminates, but the relay does not pick, check the relay coil
connections.
Failure of the green LED to illuminate, combined with a lack of relay
energy following a correct timing interval could indicate a failure of the vital
driver circuit.
P1457, Rev. Nov/07 5–8 Alstom Signaling Inc.