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SERVICE BULLETIN
PRODUCT: COMPUTER MONITOR BULLETIN: MONITOR 95-008 MODEL: SAMTRON SC-428PT/L
SUBJECT: No Raster BACKGROUND:There is a delay in the 12V/DC operation. Due to the delay the 166V/DC line operates first when power is first applied to the monitor. This will affect the horizontal circuit and cause a surge, which in turn will cause Q403 and Q408 to short.
SOLUTION: Insert a IN4937 diode into location D300 and substitute R401 (33 ohm, 1/2W) with a 220 uH coil.
PARTS LIST:
Original Parts
Location R401 D300 Parts Code Description
New Parts
Parts Code Description
911-123307FF R-Carbon, 33, 1/2w None None
925-001001AN Coil, 220 uH 893-314937AC Diode, IN4937
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 12-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-001 MODEL: CQB4147
SUBJECT: Reduce Q404 Failure Rate Causing No Raster
BACKGROUND: Q404 fails when the monitor changes from the DPMS Suspend mode back to Normal operation. Q415 is designed, in the circuit, to cut off horizontal drive to the base of Q404. This is achieved by turning Q415 on in the Suspend mode. In normal operation, Q415 is turned off. There is a delay in turning Q415 off by approximately 15 ms. This will cause an abnormal pulse at the base of Q404, causing damage to the transistor.
SOLUTION: The base current limiting resistance to Q415 has been changed by decreasing the values of R200 and R461.
PARTS LIST: ORIGINAL
Location No. R200 R461 Part No. 2001-000056 2001-000056 Description R-CF 4.7K, 1/6W R-CF 4.7K, 1/6W Part No. 2001-000043 2001-000029
NEW
Description R-CF 1K, 1/6W R-CF 100 OHM, 1/6W
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 5-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-002 MODEL: CMH7379L
SUBJECT: To prevent whistling sound from occurring.
BACKGROUND: A whistling sound is created from harmonic noise generated between T402, L402, and the main PCB near the Flyback Transformer. SOLUTION: Add a piece of rubber to insulate the main PCB solder side from the bottom metal shield. See Illustration below showing the section of the PCB where the rubber will be located.
PARTS LIST: Part No. BH61-30303A Description RUBBER
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 5-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-003 MODEL: CQB4147
SUBJECT: Improve the Horizontal Output Transistor Quality
BACKGROUND: The horizontal output for the CQB4147 has been changed as of May 1, 1997. The BU2508DF, which had been used prior to this date, has been failing intermittently due to a current surge from the 166 volt B+ line. The current surge is caused mainly from the DPMS off mode recovery. SOLUTION: The circuit has been improved by using a 2SC5149, which has a higher hfe than the originally used BU2508DF.
PARTS LIST: ORIGINAL
Location No. Q403 Part No. 0502-000007 Description BU2508DF Part No. 0502-000005
NEW
Description 2SC5149
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 5-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-004 MODEL: CFX1577L
SUBJECT: Vertical Positioning Shifted Off Center
BACKGROUND: Q302 and R327 fail in the vertical positioning circuit. The failure is caused by a current surge during power up and from the monitor recovering from an extended period in the DPMS Suspend mode.
SOLUTION: Replace Q302, Q303, and R327 with different ratings. Production went under these changes as of February 1, 1997. Observe the pin configuration when replacing Q302.
PARTS LIST: ORIGINAL
Location No. Q302 Q303 R327 Part No. 0501-000586 0501-000008 2001-000526 Description KSC945, 150mA KSC733C, 150mA R-CARBON, 1/6 W Part No. 0502-000006 0501-000294 2003-000590
NEW
Description KSC1507, 200mA KSA708, 700mA MO, 2W, 22 ohm
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV8-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-005 MODEL: CMH7379L
SUBJECT: Q407 Failure Causing No Raster or Small Horizontal Size
BACKGROUND: Q407 fails due to a transient pulse and current when mode switching from DOS to Windows. This occurs with a Matrox video card installed in the computer.
SOLUTION: Add a sub-PCB assembly as in figures 1 and 2 and a snubbing circuit for the horizontal output as in figure 3.
PARTS LIST:
ORIGINAL
Location No.
NA NA NA NA NA NA
NEW
Description
NA NA NA NA NA NA
Part No.
NA NA NA NA NA NA
Part No.
BH92-50106J BH39-40355S 6003-000129 0401-000005 0402-000012 2003-000009
Description
SUB-PCB ASSEMBLY 4 PIN CBF-HARNESS TAPTITE SCREW 1N4148 DIODE UF4007 DIODE 220 OMHS, 1 WATT
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 8-1
Figure 1 Top View of the Main Board
Figure 2 Bottom View of the Main Board
Figure 3 Snubbing Circuits
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-007 MODEL: CMB5477L
SUBJECT: Flyback Transformer Revisions
BACKGROUND: Samsung instituted new revision flyback transformers as of October 24, 1996. The new flyback transformer will prevent intermittent no raster conditions. The revised flyback transformers that have been applied to the latest production runs will have resistance values changed in the x-ray protection and the high voltage adjustment circuits. SOLUTION: When replacing a flyback transformer refer to the parts list below. The resistance values should be changed accordingly. If the resistance values are different from the flyback transformers listed below, intermittent no raster or shutdown conditions will exist. Refer back to the original parts list and schematic located in the service manual for any flyback transformer without a revision number or label on it. PARTS LIST: ORIGINAL
Location No. T402 Part No. BH26-10303V Description REV.04 FSA15A003 SAMSUNG 1/4W, 86k ohm 1/4W, 3.9k ohm 1/4W, 4.3k ohm Part No. BH26-10303V
NEW
Description REV.05 & REV.06 FSA-15A003 SAMSUNG 1/4W, 91k ohm 1/4W, 4.7k ohm 1/4W, 3.3k ohm
R516 R411 R412
2004-001319 2001-000054 2001-000722
2004-001349 2004-000899 2004-000698
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 8-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-008 MODEL: CFG9637
SUBJECT: Video Pre-amp (LM1205) Failure Causing No OSD
BACKGROUND: The OSD blanking input stage of IC101 (LM1205) shorts to the Vcc input stage due to CRT discharging and surge current.
SOLUTION: Add a 7.5V zenor diode between pin 13 of IC101 and ground (cathode to pin 13 and anode to ground). Replace jumper wire JP104 with a 100 ohm ½ watt resistor. The resistor will act as a delay and improve the R,G,B surge absorbers discharge effect. Replace the 300V spark gaps at each of the Red, Green, and Blue cathodes of the CRT with 200V surge absorbers.
PARTS LIST: ORIGINAL
Location No.
NA JP104 SGR1 SGB1 SGG1
NEW
Description Part No.
0403-000366 2001-000028 4715-000102 4715-000102 4715-000102
Part No.
NA NA 4715-000106 4715-000106 4715-000106
Description
ZD 7.5V R-CF(S), 100 ohm, 1/2W 200V, Surge Absorber 200V, Surge Absorber 200V, Surge Absorber
NA JP104 300V, Surge Absorber 300V, Surge Absorber 300V, Surge Absorber
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 8-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-009 MODEL: CMB5477L
SUBJECT: Video Pre-amp IC101 (LM1207) Failure
BACKGROUND: IC101 becomes damaged from arcing within the CRT during electronic discharge.
SOLUTION: Add a 300V spark gap in between the G1 grid of the CRT and ground. This will aid in reducing the discharge effect from the CRT.
PARTS LIST: ORIGINAL
Location No.
NA
NEW
Description
NA
Part No.
NA
Part No.
4715-000106
Description
300V, Surge Absorber
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 8-1
SERVICE BULLETIN
PRODUCT: Computer Monitor BULLETIN: MON 97-010 MODEL: CQA4147, CQB4147
SUBJECT: No Raster
BACKGROUND: D618, which is the rectifier diode for the 166V line, burns due to a reverse peak voltage that occurs when power is turned off.
SOLUTION: A snubbing capacitor must be added in parallel with D618 in order to prevent this from occurring. This capacitor should be added to all CQB and CQA chassis as a preventative maintenance.
PARTS LIST: ORIGINAL
Location No.
C643
NEW
Description
NA
Part No.
NA
Part No.
2201-000012
Description
C-CERAMIC DISK, 220pf, 10%, 1KV
Disclaimer: This information is provided "as is" without warranty of any kind either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose.
REV 8-1