HOW TO ENTER SERVICE MODE JVC AV-21L91 - AV-25L91 - AV-29L91 (POWER SUPPLY CIRCUIT)

HOW TO ENTER SERVICE MODE JVC AV-21L91 - AV-25L91 - AV-29L91 (POWER SUPPLY CIRCUIT)

CRT TV

SERVICE MODE AND POWER SUPPLY CIRCUIT

 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.

BASIC OPERATION IN SERVICE MENU
1. TOOL OF SERVICE MENU OPERATION
Operate the SERVICE MENU with the remote control unit.
2. SERVICE MENU ITEMS
With the SERVICE MENU, various settings (adjustments) can be made, and they are broadly classified in the following items of settings:
• 1.IF ...........For entering/adjusting the setting values (adjustment values) of the IF circuit.
• 2.VC .......For entering/adjusting the setting values (adjustment values) of the VIDEO/CHROMA circuit.
• 3.DEF ......For entering/adjusting the setting values (adjustment values) of the DEFLECTION circuit.
• 4.VSM PRESET ..................For setting the values of STANDARD, SOFT and BRIGHT.
(VSM:video status memory)
• 5.PRESET ...........................For setting the values of the preset.
• 6. AUDIO .............................For entering/adjusting the setting values (adjustment values) of the multiplicity sound circuit.
• 7.PLUG & PLAY (OFF). ......This is not used for service 

Selection of SUB MENU SCREEN
Press one of the keys 1 to 7 on the remote control unit, and select the SUB MENU SCREEN from the SERVICE MENU. (See Fig.1 on the
next page.)
SERVICE MENU → SUB MENU 1. IF
2. VC
3. DEF
4. VSM PRESET
5. PRESET
6. AUDIO
7. PLUG & PLAY (OFF)

Method of Setting

*Once the setting values are set, they are memorized automatically.
*It must not adjust without inputting a signal.
1) 1. IF
[1.VCO ]
(a) 1 Key......................... Select 1.IF.
(b) 1 Key......................... Select 1.VCO.
(c) DISPLAY Key ............ When this pressed twice, you will return to the SERVICE MENU.
• Under normal conditions, no adjustment is required.

[2.DELAY POINT ]
(a) 1 Key......................... Select 1. IF.
(b) 2 Key......................... Select 2.DELAY POINT.
(c) MENU –/+Key ........... Adjust the setting value.
(d) DISPLAY Key ........... When this is pressed twice, you will return to the SERVICE MENU.

2) 2. VC, 3. DEF, 4. VSM PRESET, 5. PRESET and 6. AUDIO
(a) 2 ~5 Keys .................. Select one from 2. VC, 3. DEF, 4. VSM PRESET, 5. PRESET and 6. AUDIO.
(b) MENU &/^ key ....... Select setting items.
(c) MENU –/+Key ........... Adjust the setting values of the setting items.
• Use the number keys on the remote control unit for setting of WHITE BALANCE.
For the setting, refer to each item concerned.
(d) DISPLAY Key ........... When this is pressed, you will return to the SERVICE MENU.

3) 7. PLUG & PLAY (OFF)
This is not used for service.

(4) 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.

PURITY ADJUSTMENT

1. Demagnetize CRT with the demagnetizer.
2. Loosen the retainer screw of the deflection yoke.
3. Remove the wedges.
4. Input a green raster signal from the signal generator, and turn the screen to green raster.
5. Move the deflection yoke backward.
6. Bring the long lug of the purity magnets on the short lug and position them horizontally.
7. Adjust the gap between two lugs so that the GREEN RASTER will come into the centre of the screen.
8. Move the deflection yoke forward, and fix the position of the deflection yoke so that the whole screen will become green.
9. Insert the wedge to the top side of the deflection yoke so that it will not move.
10. Input a crosshatch signal.
11. Verify that the screen is horizontal.
12. Input red and blue raster signals, and make sure that purity is properly adjusted.

SELF-CHECK FUNCTIONS

Over-current protection

An over-current on the low B line is detected.

The main microcomputer detects the possible abnormality at 30- msec.intervals and judges the results in every 16 time. Of the 16 times, if NG is detected more than 9 times, it is judged that there is an abnormality.

When an abnormality has been detected, the SUB-POWER is turned off. While the SUBPOWER is being turned off, the POWER key on the remote control unit is not operational until the power cord is taken out and put in again.

Self check indicating function

When an abnormality has been detected at about 5 seconds after the power is turned on,the SUB POWER is turned off immediately and the LEDs flash.

Over-current protection------------At 0.2-second intervals

CRT NECK protection………………At 1-second intervals

POWER SUPPLY CIRCUIT