TOSHIBA 20AS25
Service Manual

ELECTRICAL ADJUSTMENTS
1. ADJUSTMENT PROCEDURE
Read and perform these adjustments when repairing the circuits or replacing electrical parts or PCB assemblies. CAUTION � Use an isolation transformer when performing any service on this chassis. � Before removing the anode cap, discharge electricity because it contains high voltage. � When removing a PCB or related component, after unfastening or changing a wire, be sure to put the wire back in its original position. � When you exchange IC and Transistor for a heat sink, apply the silicon grease on the contact section of the heat sink. Before applying new silicon grease, remove all the old silicon grease. (Old grease may cause damages to the IC and Transistor.) Prepare the following measurement tools for electrical adjustments. 1. Oscilloscope 2. Digital Voltmeter 3. Pattern Generator On-Screen Display Adjustment 1. In the condition of NO indication on the screen. Press the VOL. DOWN button on the set and the Channel button (9) on the remote control for more than 2 seconds to appear the adjustment mode on the screen as shown in Fig. 1-1. TV

2. BASIC ADJUSTMENTS
2-1: CUT OFF 1. Adjust the unit to the following settings. R.DRIVE=10, B.DRIVE=10, R.BIAS=64, G.BIAS=64, B.BIAS=64, BRI.CENT=100, CONT.MAX=60. 2. Place the set with Aging Test for more than 15 minutes. 3. Activate the adjustment mode display of Fig. 1-1 and press the channel button (01) on the remote control to select "CUT OFF". 4. Adjust the Screen Volume until a dim raster is obtained. 2-2: WHITE BALANCE NOTE: Adjust after performing CUT OFF adjustment. 1. Place the set with Aging Test for more than 10 minutes. 2. Receive the gray scale pattern from the Pattern Generator. 3. Using the remote control, set the brightness and contrast to normal position. 4. Activate the adjustment mode display of Fig. 1-1 and press the channel button (10) on the remote control to select �R. BIAS�. 5. Press the CH. UP/DOWN button on the remote control to select the �R. BIAS�, �G. BIAS�, �B. BIAS�, �R. DRIVE� or �B. DRIVE�. 6. Adjust the VOL. UP/DOWN button on the remote control to whiten the R. BIAS, G. BIAS, B. BIAS, R. DRIVE, and B. DRIVE at each step tone sections equally. 7. Perform the above adjustments 5 and 6 until the white color is looked like a white. 2-3: FOCUS 1. Receive the monoscope pattern. 2. Turn the Focus Volume fully counterclockwise once. 3. Adjust the Focus Volume until picture is distinct.

00 OSD

28 Fig. 1-1

2-4: HORIZONTAL PHASE 1. Receive the monoscope pattern. 2. Using the remote control, set the brightness and contrast to normal position. 3. Activate the adjustment mode display of Fig. 1-1 and press the channel button (05) on the remote control to select �H. PHAS�. 4. Press the VOL. UP/DOWN button on the remote control until the SHIFT quantity of the OVER SCAN on right and left becomes minimum. 2-5: VERTICAL SHIFT 1. Receive the monoscope pattern. 2. Using the remote control, set the brightness and contrast to normal position. 3. Activate the adjustment mode display of Fig. 1-1 and press the channel button (07) on the remote control to select �V. SFT�. 4. Press the VOL. UP/DOWN button on the remote control until the horizontal line becomes fit to the notch of the shadow mask.

3. Use the Channel UP/DOWN button or Channel button (0-9) on the remote control to select the options shown in Fig. 1-2. 4. Press the MENU button on the remote control to end the adjustments.
NO. FUNCTION 00 01 04 05 06 07 08 09 10 11 12 13 14 15 OSD H CUT OFF H. VCO H. PHASE V. SIZE V. SHIFT R DRIVE B DRIVE R BIAS G BIAS B BIAS BRIGHT CENT BRIGHT MAX BRIGHT MIN NO. FUNCTION 16 17 18 19 20 21 22 23 24 25 26 27 28 29 CONTRAST CENT CONTRAST MAX CONTRAST MIN COLOR CENTER COLOR MAX COLOR MIN TINT SHARPNESS FM LEVEL LEVEL SEPARATION1 SEPARATION2 TEST MONO TEST STEREO

Fig. 1-2 D-1