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
V8 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). Connect +3.3V DC (more than 2.6V to be
precise) from the power supply to the
AUX GPI3 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 GPI3 line (to be precise
the voltage on the line should be less than 0.6V). 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 GPI2 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.
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