Tait TB7100, Service Manual

Page: 132 / 370

134 Power Supply Fault Finding TB7100 Service Manual
© Tait Electronics Limited October 2005
Task 5 —
Check Power-up
Options
The functioning of the power-up options may be checked as described in
Step 1 to Step 4 below. Carry out the procedure in the appropriate step or
steps. In all four cases the procedure involves checking the digital power-up
signal at pin 5 of IC602. For a particular option, the activation mechanism
is the condition that results in the power-up signal becoming active (the
signal is active high).
1. For the battery power-sense option the link LK1 should be inserted
(see
Figure 9.2 ). Check the power-up signal at pin 5 of IC602
(see Figure 9.1 ) while first disconnecting and then reconnecting the
13.8V DC supply at the power connector.
The power-up signal should go high when the power is reconnected.
If it does, conclude with
Step 5 . If it does not, check for continuity
and shorts to ground between the link LK1 and the
+13
V
8
BATT
input
at the power connector PL100. Repair any fault and go to Step 5 .
2. For the auxiliary power-sense option the link LK2 should be inserted
(see
Figure 9.2 ). C3.3 V DC (more than 2.6 V to be
precise) from the power supply to the
AUX GPI
3 line (pin 4 of the
auxiliary connector SK101). Check that the power-up signal at pin 5
of IC602 (see
Figure 9.1 ) is high.
Remove the +3.3V supply and ground the
AUX GPI
3
line (to be precise
the voltage on the line should be less than 0.6 V). If the power-up
signal is now low, conclude with
Step 5 . If it is not, check for
continuity and shorts to ground between D601 (see Figure 9.1 ) and
pin 4 of the auxiliary connector SK101. Repair any fault and go to
Step 5 .
3. For the emergency power-sense option the link LK3 should be
inserted (see
Figure 9.2 ). Connect the
AUX GPI
2
line (pin 5 of the
auxiliary connector SK101) to ground. Check that the power-up
signal at pin 5 of IC602 (see
Figure 9.1 ) is high.
Remove the connection to ground. If the power-up signal is now
low, conclude with
Step 5 . If it is not, check for continuity and shorts
to ground in the path from D601 (see Figure 9.1 ), via Q600
(see Figure 9.2 ), to pin 5 of the auxiliary connector SK101. Repair
any fault and go to Step 5 .