Electrical Adjustments - Memorex MT2252 Service Manual

1. BEFORE MAKING ELECTRICAL
ADJUSTMENTS
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.
Inferior silicon grease can damage IC's and transistors.
• When replacing IC's and transistors, use only specified
silicon grease (YG6260M).
Remove all old silicon before applying new silicon.
Prepare the following measurement tools for electrical
adjustments.
1. Synchro Scope
2. Digital Voltmeter
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. F U N C T I O N
00 OSD H
01 CUT OFF
02 RF AGC
03 VIF VCO
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

ELECTRICAL ADJUSTMENTS

TV
15
Fig. 1-1
N O . F U N C T I O N
13 BRIGHTNESS
14 CONTRAST
15 COLOR
16 TINT
17 SHARPNESS
18 FM LEVEL
19 LEVEL
20 SEPARATION 1
21 SEPARATION 2
22 TEST MONO
23 TEST STEREO
24 X-RAY TEST
Fig. 1-2
2. BASIC ADJUSTMENTS
2-1: RF AGC DELAY
1. Receive an 60dB monoscope pattern.
2. Connect the digital voltmeter to R606.
3. Activate the adjustment mode display of Fig. 1-1 and
press the channel button (02) on the remote control to
select "RF AGC".
4. Press the VOL. UP/DOWN button on the remote control
until the digital voltmeter is 2.65 ± 0.05V.
2-2: CUT OFF
1. Adjust the unit to the following settings.
R.DRIVE=81, B.DRIVE=65, R.BIAS=69, G.BIAS=80,
B.BIAS=70, BRIGHTNESS=135, CONTRAST=100.
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.
2-3: FOCUS
1. Receive the monoscope pattern.
2. Turn the Focus Volume fully counterclockwise once.
3. Adjust the Focus Volume until picture is distinct.
2-4: WHITE BALANCE
NOTE: Adjust after performing CUT OFF adjustment.
1. Place the set with Aging Test for more than 10 minutes.
2. Receive the color bar pattern.
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. 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 looked like a white.
2-5: SUB TINT/SUB COLOR
1. Receive the color bar pattern. (RF Input)
2. Connect the oscilloscope to TP024.
3. Activate the adjustment mode display of Fig. 1-1 and
press the channel button (16) on the remote control to
select "TINT".
4. Press the VOL. UP/DOWN button on the remote control
until the section "A" becomes as straight line.
(Refer to Fig. 2-1)
5. Connect the synchro scope to TP022.
6. Press the CH DOWN button once to set to "COLOR" mode.
7. Press the VOL. UP/DOWN button on the remote control
until the red color level is adjusted to 110% of the white
level. (Refer to Fig. 2-2)
8. Receive the color bar pattern. (Audio Video Input)
9. Press the TV/AV button on the remote control to set to
the AV mode. Then perform the above adjustments 2~7.
D1-1