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Print is Too Dark or Too Light, Peripheral circuits Q16 and RV6 on MA-99 board are

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5-2. Print is Too Dark or Too Light START Is reference voltage input to pin 2 of IC6 on MA-99 board when "CONTRAST" is set to center position? YES Peripheral circuits Q200 and Q16 on MA-99 board are NO defective. Is reference voltage input to pin 5 of Q7 on MA-99 board when "BRIGHT" is set to center position? YES Is voltage (approx. 1.5 to 2.5 V) available at pin 6 of IC304 on MA-99 board when head is at the normal temperature? YES Peripheral circuits Q16 and RV6 on MA-99 board are NO defective. Peripheral circuit IC401 and pins 29 and 30 of CN9 NO on MA-99 board, or the thermistor in the head are defective. Are required voltages available at each terminal, 3 V at pin 19 of IC500 on NO Peripheral circuit Q21 on MA-99 board is defective. MA-99 board, and 1 V at pin 23 of IC500? YES Is density of stair step printed in test mode properly? YES The head voltage or CN9 on MA-99 board is defective. NO The data buses of IC500 and IC503 on MA-99 board are defective. 5-2 UP-895/(E)

Section	Page
Cover	1
Table of Contents	3
1.Operating Instructions	7
2.Service Information	17
2-1. Board Layout	17
2-2. Disassembly	17
2-3. Removal of Major Parts	18
2-3-1. Removal of Mechanical Block	18
2-3-2. Removal of MA-99 Board	19
2-3-3. Removal of Switching Regulator	19
2-3-4. Removal of Thermal Head	20
2-4. Tightening the Screws	21
2-5. Installation of Fan Motor	22
3.Electrical Alignment	23
3-1. AGC Adjustment	23
3-2. Video Level Adjustment	23
3-3. Brightness and Contrast Adjustment	24
3-4. Head Voltage Adjustment	25
3-5. Initialization of Print Count History	25
4.Circuit Operation Description	27
4-1. Video Circuit	29
4-1-1. BNC Input Connector - Trap Filter Circuit	29
4-1-2. nC-SYNC Generator Circuit	29
4-1-3. AGC Circuit	29
4-1-4. Brightness and Contrast Control	29
4-1-5. A/D Conversion and D/A Conversion	29
4-2. Clock Generator Circuit	30
4-3. Memory and Head Control Circuit	30
4-3-1. Reading the Serial Data from System Control	31
4-3-2. Writing in Frame Memory	31
4-3-3. Transfer from Frame Memory to Line Memory	31
4-3-4. Thermal Head Control and One-Line Memory	31
4-4. System Control Section	34
4-4-1. Reading of Keys	34
4-4-2. Reading of Function Switches	34
4-4-3. Platen Motor Control	35
4-4-4. Head Up and Down Control	36
4-4-5. Monitor of Door Sensor	36
4-4-6. Monitor of Paper Sensor	36
4-4-7. Monitor of Head Temperature Sensor	37
4-4-8. Control of Head Fan Motor (for Head Cooling)	37
4-4-9. Control of Video Circuit Section	37
4-4-10. Control of Memory and Head Control Circuit	38
4-4-11. Gamma Correction and Thermal Storage Correction	39
4-4-12. Discrimination of Video Signal to be Input	39
4-4-13. Remote Interface	39
4-4-14. Storage of Print Count History	39
4-5. Thermal Head Section	40
4-5-1. Structure	40
4-5-2. Basic Operation	41
4-5-3. Stair Generation	41
4-5-4. Temperature Correction	42
4-5-5. Line Count Correction	42
5.Troubleshooting	43
5-1. Print is Faulty	43
5-2. Print is Too Dark or Too Light	44
5-3. “Paper Sensor” is Out of Order	45
5-4. Head Operation (Up & Down) is Out of Order	46
5-5. Paper Feeding is Out of Order	47
5-6. Door (Opening and Closing) is Out of Order	48
6.Service Mode (Self-diagnostic Function)	49
6-1 Printing the Test Pattern	49
6-2. Up/Down Operation of Head	50
6-3. Feed Operation	50
6-4. Display and Clearing of Print Sheet History	51
7.Semiconductor Pin Assignments	53
8.Spare Parts	55
8-1. Notes on Repair Parts	55
8-2. Exploded Views	56
8-3. Electrical Parts List	61
9.Block Diagram	69
Overall	69
10.Schematic Diagrams and Board Layouts	71
Frame	72
KY-454	73
SE-531	73
SE-532	73
SU-52	73