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Type TD-5 Class 1E Time Delay Relay
in Figure 4. The neon lamp will light if the TX relay is
operating properly.
6.1.2
Indicating Contactor Switch (ICS)
Close the main relay contacts and pass sufficient dc
current through the trip circuit to close the contacts of
the ICS. This value of current should not be greater
than the particular ICS nameplate rating. The indicator
target should drop freely.
Repeat above except pass 85% of ICS nameplate rating
current. Contacts should not pickup and target should
not drop.
6.2
ROUTINE MAINTENANCE
All relays should be inspected and checked periodically
to assure proper operation. Generally a visual inspection
should call attention to any noticeable changes.
All contacts should be cleaned periodically. A contact
burnisher S#182A836H01 is recommended for this
purpose. The use of abrasive material for cleaning
contacts is not recommended because of the danger of
embedding small particles in the face of the soft silver
and thus impairing the contact. Also, a calibration check
should be performed once a year to detect any electronic
component failures which can occur on a random basis.
Potentiometers, tantalum capacitors, and plastic cased
semi-conductors may have a common mode failure
characteristic and routine replacement is recommended
on the following schedule:
Tantalum Capacitors
Potentiometer
Rheostat
Diodes
Recalibration is necessary whenever any of these
components are changed.
C, C1 to C7
10 years
P
5 years
T
5 years
D1 to D6
10 years
6.3
TROUBLE SHOOTING PROCEDURE
Use the following procedure to locate the source of
trouble if the TD-5 is not operating correctly.
1. Inspect all wires and connections, paying particular
attention to telephone relay and printed circuit board
terminals.
2. Check the reference voltage circuit. This is done by
measuring the dc voltage across the silicon power
regulator, Z or Z1. Connect the dc voltmeter positive
terminal to the bottom terminal of RS and the
negative terminal to relay terminal 8. Apply rated
voltage per the test circuit diagram, Figure 4. The
Zener voltage should be between 11.0 and 14.0 volts
for 24/32 VDC relays, between 21.5 and 25.5 volts
for 48/125 VDC relays, and between 50 and 59 volts
for 250 VDC relays.
3. Check the timing capacitor voltage and the P
potentiometer brush voltage with an oscilloscope
or a high resistance dc voltmeter.
Connect between adjustable terminal of P and relay
terminal 8.
The brush voltage, which is constant until the TR
relay trips, should be approximately one half the
reference voltage. The capacitor should gradually
change to the potentiometer brush voltage, plus
approximately one volt for silicon junction forward
voltage drops through SCR and D2.
4. If reference voltage, capacitor voltage, and
potentiometer voltage all appear to be correct, the
SCR may be the cause of trouble. The anode to
cathode voltage, as measured, should be
approximately one-half the reference voltage until
the capacitor voltage reaches the P brush voltage,
at which time the anode to cathode voltage should
drop to approximately one volt.
41-579.11B
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