Replacement Of Memory Ic; Service Adjustment - NEC PF-68T31 Service Manual

REPLACEMENT OF MEMORY IC

1. MEMORY IC.
This TV uses memory IC. In the memory IC are memorized data for correctly operating the video
and deflection circuits.
When replacing memory IC, be sure to use IC written with the initial value of data.
2. PROCEDURE FOR REPLACING MEMORY IC
(1) Power off
Switch the power off and unplug the power cord from AC outlet.
(2) Replace IC
Be sure to use memory IC written with the initial data values.
(3) Power On
Plug the power cord into the AC outlet and switch the power On.
(4) Check and set SYSTEM default value:
1) Press "TEST" key on the special service use Remote control unit.
2) The "TEST" will be displayed on the screen.
3) Press "0" to "8" key, (Mkey) and corresponding on-screen display will be appeared.
4) In this section, except "3", "4" and "5" key function would be confirmed.
5) Check the setting value of the SYSTEM default value of Table 1. If the value is different,
select items by [CH+]/[CH-] keys and set value by [VOL+]/[VOL-] keys.
6) Press "TEST" key again and return to the normal screen.

SERVICE ADJUSTMENT

B1 POWER SUPPLY
1. Receive normal colour bar signal.
2. Connect DC voltmeter to TP91 and isolated ground.
3. Adjust VR651 to get the voltage as 130V ±1.0V.
FOCUS ADJUSTMENT
1. Receive a crosshatch signal.
2. While watching the screen, adjust the FOCUS VR to make the vertical and horizontal lines as
fine and sharp as possible.
STEREO ADJUSTMENT (PF-68T31)
1. Receive A2 stereo signal.
2. Adjust L3101 to get the voltage at TP1 (N3101 Pin #3) as 2.5V ±0.1V
3. Adjust VR3101 to get same amplitude at TP3 and TP4.
BUS CONTROL ADJUSTMENT
To enter BUS control mode, use special remote control with "TEST" key, and push "TEST" key.
On TV screen "TEST" will be indicated, this means entered bus control mode.
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