Will Not Power-Up, No Display - Bosch ACS 753 Repair Instructions

Diagnostics and Testing
Will Not Power Up, No Display
1. Verify the unit is connected to a known good
power source with a good ground and not
through an extension cord.
2. Verify the power cable is wired correctly
and the connector has not been damaged.
Replace or repair as required.
3. If unit does not power up, check to make
sure the circuit breaker hasn't tripped.
4. Turn on the main power switch.
5. If the display does not activate, verify line
voltage is present at the input and output
terminals of the switch.
• If line voltage is not present at power
switch input, check connections between
the power switch and AC connector.
• If line voltage is present at power switch
input, but not at output with switch turned
on, replace the power switch.
• If line voltage is present at both input and
output of switch, proceed to next step.
Circuit Breaker Not Tripped
1. Turn off unit and disconnect AC power cord
from receptacle.
2. Check the circuit breaker for continuity.
• If there is no continuity, replace circuit
breaker.
• If there is continuity, continue to next step.
NOTE: Before replacing any component, make
sure the interconnecting harnesses are in good
condition and proper electrical contact is made
between the connectors.
3. Perform the following continuity checks:
a. Disconnect the cable from power supply
PSJ1.
b. Jumper all input power cable pins
together at the plug end.
c. Check for continuity across power
supply input cable pins 2 and 3.
• If continuity exists, remove jumpers
from the input power cable and connect
PBP3.
• If no continuity, check the power switch
for proper operation. Repair or replace
as required.
SP00D00609 2018-03-26
ACS 753, ACS 763, ACS 863 Service Manual
4. Connect the unit to a proper AC power
source and place the unit power switch on.
The display should illuminate. If the unit
is still inoperative, perform the following
voltage checks.
a. Measure the voltage at the output of the
power supply from PSJ2 pin 2 (+) to pin
3 (-). Voltage should be 12 VDC.
• If 12V is not present, go to step 5.
• If 12V is present, replace control board.
5. Connect the unit to a proper AC power
source and place the unit power switch on.
a. Disconnect the cable from power board
PBP4.
b. Measure the voltage at PBP3 pins 2
and 3.
• Voltage should be 230 VAC (nominal).
If voltage is correct, replace power
supply.
• If voltage is less than 207 VAC, replace
power board.
Circuit Breaker Tripped
1. Place unit power switch off and reset the
circuit breaker.
2. Place unit power switch on. If the circuit
breaker remains engaged, the unit should
operate normally and no further action is
required. Otherwise, proceed to step 3.
3. If the circuit breaker trips again after being
reset, place the power switch off.
4. Disconnect PBP3 and perform continuity
checks of the power switch. If no faults are
found, replace the circuit breaker.
5. Connect PBP3 and disconnect remaining
connectors from the power board.
6. Place unit power switch on.
7. If the reset circuit breaker trips again,
replace the power board.
8. If the circuit breaker doesn't trip after being
reset, place the power switch off.
9. Connect one connector at a time into the
power board, placing the power switch on
after each additional connection.
10. Perform step 9 until the circuit breaker trips
when placing the power switch on.
11. Check all components associated with the
last connector to be attached to the power
board when the power switch was placed
on.
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Robert Bosch GmbH