Monday, December 14, 2015

JVC AV-25VT15 Service mode and adjustments

JVC AV-25VT15 

REPLACEMENT OF MEMORY IC
MEMORY IC
This TV uses the following memory IC.
Memory IC: IC702 on MAIN PWB
The memory IC memorizes data for correctly operating the video and deflection circuits. When replacing the memory IC, be sure to use the same type IC written with the initial values of data. In other words, use the specific IC listed in "PRINTED WIRING BOARD PARTS LIST". For its mounting location, refer to "ADJUSTMENT LOCATIONS".
PROCEDURE FOR REPLACING MEMORY IC
1. Power off
Switch the power off and unplug the power cord from the wall outlet.
2. Replacing the memory IC
Replace the memory IC with new one. Be sure to use the memory IC written with the initial data values.
3. Power on
Plug the power cord into the wall outlet and switch the power on.
4. Check and setting of SYSTEM CONSTANT SET:
(1) Press the [DISPLAY] key and the [PICTURE MODE] key on the remote control unit simultaneously.
The SERVICE MENU screen will be displayed.
(2) In the SERVICE MENU, press the [DISPLAY] key and [PICTURE MODE] key simultaneously. Then, the SYSTEM CONSTANT SET screen will be displayed.
(3) Check the setting values of the SYSTEM CONSTANT SET .
(4) Press the [DISPLAY] key twice to return to the normal screen.
5. Receive channel setting
Refer to the OPERATING INSTRUCTIONS and set the receive channels (channels preset).
6. User setting
For setting, refer to the OPERATING INSTRUCTIONS.
7. Setting of SERVICE MENU
Verify the setting for each setting item in the SERVICE MENU. If readjustment is necessary items.
ADJUSTMENT PREPARATION
(1) You can make the necessary adjustments for this unit with either the remote control unit or with the adjustment equipment and parts as given below.
(2) Adjustment with the remote control unit is made on the basis of the initial setting values, however, the new setting values used for setting the screen to its optimum condition may differ from the initial settings.
(3) Make sure that AC power is turned on correctly.
(4) Turn on the power for the set and test equipment before use, and start the adjustment procedures after waiting at least 30 minutes.
(5) Unless otherwise specified, prepare the most suitable reception or input signal for adjustment.
(6) Never touch any adjustment parts, which are not specified in the list for this variable resistors, transformers, trimmer capacitors, etc.
HOW TO ENTER SERVICE MENU
Press the [DISPLAY] key and the [PICTURE MODE] key on the remote control unit simultaneously. The SERVICE MENU screen will be displayed.
Release of SERVICE MENU
After completing the setting, return to the SERVICE MENU by pressing the [DISPLAY] key, then again press the [DISPLAY] key to return to the normal screen.
FOCUS adjustment
Set PICTURE MODE (VSM) to "BRIGHT".
# The final adjustment of CONVERGENCE must be done after the FOCUS adjustment. (CONVERGENCE is affected by the FOCUS adjustment.) If any aeviation in CONVERGENCE is found, PURITY must be adjusted to restore the convergence.
(1) Receive a crosshatch signal.
(2) Adjust the FOCUS VR so that the vertical and horizontal lines will be clear and in fine detail on the screen.
(3) Make sure that the picture is in focus even when the screen gets darkened.
DELAY POINT (AGC TAKE-OVER) adjustment
(1) Receive a black and white broadcast signal (color off).
(2) Select 1. IF from the SERVICE MENU.
(3) Select 2. DELAY POINT.
(4) Adjust in order to eliminate any noise or beat from the image. Any increase above the initial value produces the noise and any decrease below it produces the beat.
(5) Press the [DISPLAY] key three times to return to the normal screen.
(6) Turn to other channels and make sure that there are no irregularities.
WHITE BALANCE (Low light) adjustment
# Set PICTURE MODE (VSM) to "BRIGHT".
COMPOSITE WHITE BALANCE -
(1) Receive a PAL black and white signal (color off).
(2) Select 2. V/C from the SERVICE MENU.
(3) Select 2. CUTOFF (B) and (G).
(4) Set each value to initial setting value with the [4] /
[7] keys and [5] / [8] keys.
(5) Turn the SCREEN VR fully counterclockwise, then slowly turn it clockwise to where a red, blue or green color is faintly visible.
(6) Use the [4] / [7] and [5] / [8] keys to adjust so that the other 2 colors appear white.
(7) Turn the SCREEN VR to where the single horizontal line glows faintly.
(8) Press the [DISPLAY] key twice to return to the normal screen.
COMPONENT WHITE BALANCE -
(1) Receive a PAL component black and white signal (color off).
(2) Select VIDEO-2 SET from the MENU and set VIDEO-2 SET to COMPONENT.
(3) Adjust COMPONENT WHITE BALANCE in the same way as ”COMPOSITE WHITE BALANCE”.
SUB BRIGHT adjustment
# Proceed to the following adjustment after having completed the WHITE BALANCE (Low light) and WHITE BALANCE (High light) adjustment.
# Set PICTURE MODE (VSM) to "BRIGHT".
(1) Receive a broadcast.
(2) Select 2. V/C from the SERVICE MENU.
(3) Select 4. BRIGHT.
(4) Set the initial setting value.
(5) If the brightness is not best with the initial setting value, make fine adjustment until you get the best brightness.
(6) Press the [DISPLAY] key twice to return to the normal screen.