Electrical Adjustments - Memorex MT2274A Service Manual

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 with a heat sink,
•
apply silicon grease on the contact section of the heat
sink. Befor 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. Multi-sound Generator
4. 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 1
second to appear the adjustment mode on the screen as
shown in Fig. 1-1.
00 OSD
2. Use the Channel UP/DOWN button or Channel button
(0-9) on the remote control to select the options shown
in Fig. 1-2.
3. Press the MENU button on the remote control to end the
adjustments.
NO. FUNCTION
00 OSD H
01 CUT OFF
04 H.VCO
05 H.PHASE
06 V.SIZE
07 V.SHIFT
08 R.DRIVE
09 B.DRIVE
10 R.BIAS
11 G.BIAS
12 B.BIAS
13 BRIGHT CENT
14 BRIGHT MAX
15 BRIGHT MIN

ELECTRICAL ADJUSTMENTS

TV
17
Fig. 1-1
NO. FUNCTION
16 CONTRAST CENT
17 CONTRAST MAX
18 CONTRAST MIN
19 COLOR CENT
20 COLOR MAX
21 COLOR MIN
22 TINT
23 SHARPNESS
24 FM LEVEL
25 LEVEL
26 SEPARATION 1
27 SEPARATION 2
28 TEST MONO
29 TEST STEREO
Fig. 1-2
2. BASIC ADJUSTMENTS
2-1: CONSTANT VOLTAGE
1. Place the set in AV MODE without signal.
2. Connect the digital voltmeter to the TP401.
Adjust the VR502 until the digital voltmeter is 120 ± 0.5V.
3.
2-2: CUT OFF
1. Place the set in Aging Test for more than 15 minutes.
2. Place the set in AV MODE without signal.
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 (01) on the remote control to
select "CUT OFF".
5. Adjust the Screen Volume until a dim raster is obtained.
2-3: WHITE BALANCE
NOTE: Adjust after performing CUT OFF adjustment.
1. Place the set in Aging Test for more than 15 minutes.
2.
Receive the white 100% signal from the Pattern
Generator.
3. Using the adjustment 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. Using the VOL. UP/DOWN button on the remote control,
adjust the R.BIAS.
6. Press the CH. UP/DOWN button on the remote control to
select the "R.DRIVE", "B.DRIVE", "G.BIAS" or "B.BIAS".
7. Using the VOL. UP/DOWN button on the remote control,
adjust the R.DRIVE, B.DRIVE, G.BIAS or B.BIAS.
8. Perform the above adjustments 6 and 7 until the white
color is achieved.
2-4: FOCUS
1. Receive the monoscope pattern.
2. Turn the Focus Volume fully counterclockwise once.
3. Adjust the Focus Volume until picture is distinct.
2-5: VERTICAL POSITION
1. Receive the monoscope pattern.
2. Using the remote control, set the brightness and contrast
to normal position.
3. Adjust the VR401 until the horizontal line becomes fit to
the notch of the shadow mask.
(Refer to Fig. 2-1)
D-1
horizontal line
Notch
Shadow mask
Fig. 2-1