5. +35 V Line Over Current Protection Circuit
The +35 V line over current control circuit is illustrated below.
When the +35 V line becomes less than 27 V, Q82 and Q54 turn on, and PC1 turns on. Consequently, Q32
and Q31 turn off, and then switching FET Q1 shuts off. When the protection circuit operates, this protection
can only be removed by turning the power off and on again.
6. +5 V Line Over Current Protect Circuit
+5 V line over current control circuit is shown below.
Port 2 of IC51 (TL494CN) monitors the +5 V line, and this protection circuit operates when the +5 V line
goes below 4.75 V. When this circuit operates, port 8 signal output of the PWM pulse stops, and Q51 stops
its switching operation. Consequently, the +5 V line stops generating.
+35V Line
GND
Q53
R70
R71
R72
R73
Q54
Q82
C57
R74
R75
R54
R68
3
4
6
5
D85
Q31
PSC
Figure 2-27 +35 V Line Over Current Protection Circuit
+5v Line
GND
R53
R88
R64
R65
-
+
-
+
R67
IC51
TL494CN
2
1
D51
L51
8
R51
+35V Line
R61
Q51
Figure 2-28 +5 V Line Over Current Protection Circuit
Operating Principles
LQ-2170 Service Manual
2-20
Rev.A
Summary of Contents for LQ-2170
Page 1: ...EPSON TERMINAL PRINTER LQ 2170 SERVICE MANUAL EPSON 4005735 ...
Page 5: ...REVISION SHEET Revision Issued Date Revision Page Rev A December 5 1995 1st issued ...
Page 11: ...Figure 1 1 Exterior View of the LQ 2170 Product Description LQ 2170 Service Manual 1 2 Rev A ...
Page 80: ......
Page 127: ...1 Abnormal CR Operation LQ 2170 Service Manual Troubleshooting Rev A 5 5 ...
Page 141: ...LQ 2170 Service Manual Troubleshooting Rev A 5 19 ...
Page 156: ...Appendix LQ 2170 Service Manual A 10 Rev A ...
Page 158: ...Appendix LQ 2170 Service Manual A 12 Rev A ...
Page 159: ...Figure A 3 C165 PSB Board Assembly Circuit Diagram LQ 2170 Service Manual Appendix Rev A A 13 ...
Page 160: ...Appendix LQ 2170 Service Manual A 14 Rev A ...
Page 161: ...Figure A 4 C165 PSE Board Assembly Circuit Diagram LQ 2170 Service Manual Appendix Rev A A 15 ...
Page 162: ...Appendix LQ 2170 Service Manual A 16 Rev A ...
Page 167: ...Figure A 9 LQ 2170 Exploded Diagrams 2 LQ 2170 Service Manual Appendix Rev A A 21 ...
Page 168: ...Figure A 10 LQ 2170 Exploded Diagrams 3 Appendix LQ 2170 Service Manual A 22 Rev A ...
Page 169: ...Figure A 11 C S F Bin1 Exploded Diagrams 1 LQ 2170 Service Manual Appendix Rev A A 23 ...
Page 170: ...Figure A 12 C S F Bin1 Exploded Diagrams 2 Appendix LQ 2170 Service Manual A 24 Rev A ...
Page 171: ...Figure A 13 C S F Bin2 Exploded Diagrams LQ 2170 Service Manual Appendix Rev A A 25 ...
Page 172: ...Table A 15 Part No Reference Table Appendix LQ 2170 Service Manual A 26 Rev A ...
Page 173: ...Table A 15 Part No Reerence Table Continue LQ 2170 Service Manual Appendix Rev A A 27 ...
Page 174: ...Appendix LQ 2170 Service Manual A 28 Rev A ...
Page 175: ...EPSON Printed in Japan 95 12 05 S ...