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Sony UP895 Service Manual - Page 37

Monitor of Head Temperature Sensor, 4-4-8. Control of Head Fan Motor (for Head Cooling)

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4-4-7. Monitor of Head Temperature Sensor The change in the resistance value of the thermistor inside a thermal head is converted into a voltage using a head temperature detector circuit (IC401) and read by a system control (IC304). The voltage value is converted from analog to digital. Density (gamma) correction, fan motor control for head cooling, and head-in cleaning discrimination are performed according to the digital value. 4-4-8. Control of Head Fan Motor (for Head Cooling) The head fan motor is operated when a system control (IC304) controls driving transistors (Q400 and Q403). The head fan motor is turned on when the head temperature is more than approximately 50 dC or during printing. Operation of head fan motor IC304-26 pin L H Operation OFF ON 4-4-9. Control of Video Circuit Section A system control (IC304) controls the video circuit section as shown in the table below. IC304 I/O 77pin O 59pin O 60pin O 53pin O Function Switches THRUE and EE signals. Sets the trap filter to ON or OFF. Selects NTSC or PAL. Sets the AGC function to ON or OFF. L: ON H: OFF L: ON H: OFF L: When an NTSC signal is input H: When a PAL signal is input L: ON H: OFF UP-895/(E) 4-11

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