Tatung VM77S Service Manual - Alignments and Adjustments

Page 14

Alignments and Adjustments

 VM77S

4

Alignments and Adjustments

This section of the service manual explains how to make permanent adjustments to the monitor settings.

4-1 General Adjustments

4-1-1 Adjustment Conditions

a) Power Supply

Apply AC 115 V or 220 V

b) Warm-up Time

The monitor must be powered on for 15 minutes before starting any alignment, but requires 30 minutes of

warm-up time for convergence adjustment.

c) Signal Input

1. Video: RGB Analog, 0.7 Vp-p, positive

2. Synchronization: Horizontal and vertical TTL signal, separate, positive or negative

3. All adjustments should be made using a signal of FH = 68.68 kHz, FV = 85 Hz, unless otherwise

defined.

4-1-2 Equipment Required

The following equipments are necessary for adjustment procedures:

1. Volt-ohm-A meter (Sanwa FD-750C or equivalent)

2. 30 kV high voltage probe (HP34111A)

3. Oscilloscope (TEK2235 or equivalent)

4. Minolta Color Analyzer II

5. Signal generator (IBM PC with proper display cards or Chroma 2000)

6. Screwdriver

4-1-3 Switching Power Supply and Regulator Adjustment

a. The regulated B+ control has been preset in the factory and needs no adjustment.  However, if any repair

is made on the power supply section, the following readjustment procedures are recommended:

1. Allow the monitor to warm-up for about 15 minutes.

2. Apply VGA (1024 x 768 @ 68.68 kHz/85 Hz) signal to the monitor.

3. Connect a DC voltage meter to TP001 (on the Main board), and adjust VR801 for 11.7 ± 0.1 Vdc

4. If a fuse is broken during adjustment, remember to replace it with the exact same type of fuse.

b. If necessary, follow the following procedures to enter the factory mode.

1. Press both 

1

 key and 

2

 key simultaneously then power ON.

2. After turn the power off, this monitor will go back to normal mode.