Repairing The C166Psb/Pse Board Assembly - Epson 2070 - LQ B/W Dot-matrix Printer Service Manual

Troubleshooting
5.4 REPAIRING C166 PSB/PSE BOARD ASSEMBLY
This section provides instructions to repair a defective power supply board assembly. It describes various
symptoms, likely causes, and checkpoints. Checkpoints refer to proper waveforms, resistances, and other
values to check when evaluating the operation of any potentially faulty component. Check these values
and take the appropriate action.
Note:
This information is necessary only for servicers who repair to the component level. Servicers who repair to
the unit level (including all servicers in the U.S.) can ignore this section.
The OPERATE switch on the control panel only turns the secondary power circuit on or off, so
the primary circuit is live as long as the printer is connected to an AC power outlet. Before, you
repair or touch the power supply board, be sure to disconnect the AC power outlet.
Table 5-6. Repairing the C166 PSB/PSE Board Assembly
Problem
The 35 V and
5 V lines are
not output
The diode bridge DB1
when the
printer is
powered on.
The transformer coil is
^
open.
5-10
WARNING
Cause
Measure the DC voltage between the pins
3 and 4 of the DB1.
is dead.
Measure the resistance of T1 transformer
coils at pins 12-15, 9-11, 7-8, 3-4.
LQ-2070 Service Manual
Checkpoint Solution
Replace
the DB1.
Replace
the T1.
Rev. A