Troubleshooting Transmission Power Circuit Of Heat Source Unit - Mitsubishi Electric PQHY-P72TYHMU-A Service Handbook

[ IX Troubleshooting ]
[THMU-A]

(2) Troubleshooting transmission power circuit of heat source unit

Check the voltage at the indoor/heat source
transmission terminal block (TB3) of heat source unit.
DC 24 ~ 30 V
Check the voltage at TB3 after removing transmission line from TB3.
DC 24 ~ 30 V
Check whether the male connector is connected to
the female power supply connector (CN40).
NO
Check voltage of terminal block for centralized control (TB7).
Check voltage of TB7 by removing transmission line from TB7.
Check the voltage between No.1 and No.2 pins of the
CNS2 on the control board.
Check the voltage between No.1 and No.2 pins of the
CN102 on the power supply board for the transmission line.
Check the voltage between No.1 and No.3 pins of
the CNDC on the INV board.
DC265 ~ 357V
Check the voltage between SC-P1 and TB-N on the INV board.
DC265 ~ 357V
Check the voltages among SC-R, SC-S, and
SC-T on the INV board.
AC188 ~ 253V
Check the voltages among TB21, TB22, and
TB23 on the noise filter.
AC188 ~ 253V
Check the voltage at the power supply terminal block TB1.
AC188 ~ 253V
HWE09080
YES
NO
YES
NO
Connected
YES
YES
DC24 ~ 30V
NO
NO
YES
DC24 ~ 30V
NO
YES
DC24 ~ 30V
NO
YES
DC24 ~ 30V
NO
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
NO
Check whether the transmission line is disconnected,
check for contact failure, and repair the problem.
Check if the indoor/heat source transmission line
is not short-circuited, and repair the problem.
Check the wiring between the control board and power
supply board for the transmission line (CN102 and CNIT),
and check for proper connection of connectors.
YES
Is there a wiring
Fix the wiring and connector
error or a connector
disconnection.
disconnection?
Check for shorted transmission
line for centralized control.
Replace the control board.
YES
Is there a connector
Fix the connector disconnection.
disconnection?
NO
Check the voltage between No.5 and No.2 pins
of the CNIT on the control board.
YES
Is the voltage
Replace the M-NET board
measurement between
4.5 and 5.2 VDC?
Replace the M-NET board
Check the inrush current resistance (R1).
Replace the inrush current
NO
limiting resistor.
22 10%
YES
Replace the INV board.
Replace the INV board.
Check the wiring between the noise filter and the
INV board as well as screw tightness, and fix any
problems found.
Replace the noise filter.
Check and fix any power supply wiring and main power
supply problems found.
- 340 -
Turn on the
power again.
GB