Epson DLQ-3000 Service Manual page 109

Table 5-8. BOARD ASSY., C124 PSB/PSE Repair (Continued)
Trouble
enon
All the
output
voltages
are
abnormal.
Because
of the
circuit
structure,
when the
output is
abnormal,
output
all the
voltage
other
is ab-
Output
normal.
voltages
are
affected.
output is
abnormal.
When the
output is
normal.
Cause
Check that transistor Q154 is not
turned ON (i.e. the collector has not
reached the GP level = max. voltage).
The current
IfQ154 is OFF, some component
limiting circuit
behind PCI02 and the main switching
is bad.
circuit (Q1OZ2O2) is bad. If Q155 is
ON, Q153,Q253 or some component
behind Q154 is bad.
Check that transistor Q155 is not
turned ON (i.e. the collector has not
reached the GP Ievel=max. voltage). If
Q155 is OFF, some component behind
PC102 and the main switching circuit
(Q1022O2) is bad. IfQ155 is ON,
component is bad.
Q155 turns ON when the +5V output is
too high.
The voltage
Check transistor Q155 is not turned ON
(i.e. the collector has not reached the
GP level= min. voltage). If Q155 is
ON, IC 151 or some other component
is bad. When Q155 is OFF, some
component behind PC102 is bad.
Since PC102 is a photo-thyristor,once
it turns on,it never turn OFF until the
Therefore, the operator should wait for
a few minutes before turning the power
on again.
Investigate the waveform at pin 4 of
photo-coupler PC101 and 201.
When it is normal,a waveform with a
constant interval should be seen (with
no load). If the waveform is abnormal,
The stabiliz-
PC1OI, PC201, ZD151, ZD181 -185
ing circuit for
or a peripheral component is bad. If the
the +35V is
waveform is normal, check that the
bad.
switching waveform ofQ101 or Q201 is
normal. Then check the operation of
the peripheral components.
See Figure 5-10.
Check the voltage at pin 12 of IC151.
If the input voltage of pin 12 is normal,
Check that the correct DC voltage
The smooth-
and (+) terminals of Cl 54.
ing circuit is
bad. If there is no output vottage, L151 or
Cl 54 is bad.
Item to Check
Troubleshooting
shooting
Replace
associated
components.
Replace the
associated
bad
components.
Replace the
associated
components.
Replace
peripheral
components.
5-13