Electronic Parts Troubleshooting Guide - Lennox LT-B3021HW Installation Operating & Maintenance Manual

Electronic Parts Troubleshooting Guide

Possible Trouble 1
Is the input voltage
AC220V?
YES
Is the output voltage
of transformer about AC14V?
YES
Is the input voltage
of IC01D DC14V?
YES
Is the output voltage
of IC01D DC12V?
YES
Is the output voltage
of IC02D DC5V?
YES
Is the PIN 31,32 of
MICOM. DC5V?
YES
Exchange MICOM.
: The unit does not operate.
NO
Is shorted the
NO
transformer output?
NO
NO
NO
NO
NO
YES
–40–
Check the FUSE
and the wiring diagram.
Check the main P.C.B
pattern.
Exchange
the transformer.
Check the D02D~D05D.
Exchange IC01D.
Exchange IC02D.
Check the
5V P.C.B pattern.