Master Electronics Repair !

Welcome to Master Electronics Repair! website.Here you will find:Service Modes, Circuit Diagrams,Service manuals, Firmware Update procedure, Disassemble procedure, Universal remote control setup codes, Troubleshooting, Diagnosing, Measuring, and more.... of many of LCD/LED TV/Displays,others various electronic apparates,trough many technical notes and tips/tricks to help repairing/fixing Troubles/ faults,for electrical technicians.This site helps you to save the Earth from electronic waste!

Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and technical information about Service Modes, Circuit Diagrams, Firmware Update procedure, Disassemble procedure, Universal remote control set-up codes, Troubleshooting and more....

If you go into the profession, you will obtain or have access to a variety of tech tips databases HERE IT IS Master Electronics Repair !.

These are an excellent investment where the saying: 'time-is-money' rules. However, to learn, you need to develop a general troubleshooting approach - a logical, methodical, method of narrowing down the problem. A tech tip database might suggest: 'Replace C536' for a particular symptom. This is good advice for a specific problem on one model. However, what you really want to understand is why C536 was the cause and how to pinpoint the culprit in general even if you don't have a service manual or schematic and your tech tip database doesn't have an entry for your sick TV or VCR.

While schematics are nice, you won't always have them or be able to justify the purchase for a one-of repair. Therefore, in many cases, some reverse engineering will be necessary. The time will be well spent since even if you don't see another instance of the same model in your entire lifetime, you will have learned something in the process that can be applied to other equipment problems.
As always, when you get stuck, checking out a tech-tips database may quickly identify your problem and solution.In that case, you can greatly simplify your troubleshooting or at least confirm a diagnosis before ordering parts.

Happy repairing!

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

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Tuesday 4 August 2020

JVC AV20F703 COLOR TV HOW TO ENTER THE SERVICE MODE FOR ADJUSTMENTS - FULL SCHEMATIC

How to enter the service mode of JVC AV-20F703 color TV, service mode adjustments, full schematic

JVC AV20F703 color television service mode, adjustments, schematic

[Use one among the following instructions to enter the service mode to JVC TVs]

Press the muting key and the recall key of the remote control unit at the same time to display the service menu. To exit the service menu, turn off the power.

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.

Use the Channel UP/DOWN button or Channel button (0-9) on the remote control to select the options.

Press the MENU button on the remote control to end the adjustments.

Basic adjustments

Constant voltage
Set condition is AV MODE without signal.
Connect the digital voltmeter to the TP002.
Adjust the VR502 until the DC voltage is 116 +/-1V. RF AGC

Place the set with Aging Test for more than 15 minutes.
Receive the VHF HIGH (63dB).
Connect the digital voltmeter between the pin 5 of CP101 and the pin 1 (GND) of CP101.
Activate the adjustment mode display and press the channel button (02) on the remote control to select “RF AGC”.
Press the VOL. UP/DOWN button on the remote control until the digital voltmeter is 2.1 +/- 05V

Cut off

Adjust the unit to the following settings.
G. DRIVE=64, B. DRIVE=64, R. BIAS=64, G. BIAS=64, B. BIAS=64
Place the set with Aging Test for more than 15 minutes.
Activate the adjustment mode display and press the channel button (01) on the remote control to select “CUT OFF”.
Adjust the Screen Volume until a dim raster is obtained.

White balance. [Adjust after performing cut off adjustment.]

Place the set with Aging Test for more than 10 minutes.
Receive the gray scale pattern from the Pattern Generator. Using the remote control, set the brightness and contrast to normal position.
Activate the adjustment mode display and press the channel button (13) on the remote control to select “R. BIAS”.
Press the CH. UP/DOWN button on the remote control to select the “R. BIAS”, “G. BIAS”, “B. BIAS”, “B. DRIVE” or “G. DRIVE”.
Adjust the VOL. UP/DOWN button on the remote control to whiten the R. BIAS, G. BIAS, B. BIAS, B. DRIVE, and G. DRIVE at each step tone sections equally.
Perform the above adjustments 5 and 6 until the white color is looked like a white.

Focus

Receive the monoscope pattern.
Turn the Focus Volume fully counterclockwise once.
Adjust the Focus Volume until picture is distinct.

Horizontal position

Receive the monoscope pattern.
Using the remote control, set the brightness and contrast to normal position.
Activate the adjustment mode display and press the channel button (04) on the remote control to select “H. POSI”.
Press the VOL. UP/DOWN button on the remote control until the SHIFT quantity of the OVER SCAN on right and left becomes minimum.

Vertical position

Receive the monoscope pattern.
Using the remote control, set the brightness and contrast to normal position.
Activate the adjustment mode display and press the channel button (05) on the remote control to select “V. POSI”.
Press the VOL. UP/DOWN button on the remote control until the horizontal line becomes fit to the notch of the shadow mask.

Vertical size

Receive the monoscope pattern.
Using the remote control, set the brightness and contrast to normal position.
Activate the adjustment mode display and press the channel button (07) on the remote control to select “V. SIZE”.
Press the VOL. UP/DOWN button on the remote control until the SHIFT quantity of the OVER SCAN on upside and downside becomes 9 +/- 2%.

Vertical linearity [Adjust after performing adjustments in section 2-8. After the adjustment of Vertical Linearity, reconfirm the Vertical Position and Vertical Size adjustments.]

Receive the monoscope pattern.
Using the remote control, set the brightness and contrast to normal position.
Activate the adjustment mode display and press the channel button (09) on the remote control to select “V. LIN”.
Press the VOL. UP/DOWN button on the remote control until the SHIFT quantity of the OVER SCAN on upside and downside becomes minimum.

Level

Receive the monoscope pattern (70dB).
Connect the AC voltmeter to pin 6 of CP101 and the pin 1 (GND) of CP101.
Activate the adjustment mode display and press the channel button (36) on the remote control to select “LEVEL”.
Press the VOL. UP/DOWN button on the remote control until the AC voltmeter is 75 +/-2mV.

Sub brightness

Activate the adjustment mode display and press the channel button (16) on the remote control to select “BRI. CENT”.
Press the VOL. UP/DOWN button on the remote control until the brightness step No. becomes “50”.
Receive a broadcast and check if the picture is normal.
Press the INPUT button on the remote control to set to the AV mode. Then perform the above adjustments 1~3.
Press the INPUT button on the remote control to set to the CS mode. Then perform the above adjustments 1~3

TINT/color cent

Receive the color bar pattern. (RF Input)
Connect the oscilloscope to TP806.
Using the remote control, set the brightness, contrast, color and tint to normal position.
Activate the adjustment mode display and press the channel button (26) on the remote control to select “TINT”.
Press the VOL. UP/DOWN button on the remote control until the section “A” becomes a straight line
Connect the oscilloscope to TP804.
Press the channel button (24) on the remote control to select “COL. CENT”.
Adjust the VOLTS RANGE VARIABLE knob of the oscilloscope until the range between white 100% and 0% is set to 4.4 scales on the screen of the oscilloscope.
Press the VOL. UP/DOWN button on the remote control until the red color level is adjusted to 115 +/-10% of the
white level.
Receive the color bar pattern. (Audio Video Input)
Press the INPUT button on the remote control to set to the AV mode. Then perform the above adjustments 2~9.
Press the INPUT button on the remote control to set to the CS mode.
Activate the adjustment mode display and press the channel button (26) on the remote control to select “TINT”.
Press the VOL. UP/DOWN button on the remote control until the tint step No. becomes “50”.
Press the channel button (24) on the remote control to select “COL. CENT”.
Press the VOL. UP/DOWN button on the remote control until the color step No. becomes “62”.
Receive a broadcast and check if the picture is normal.

Contrast max manual

Activate the adjustment mode display of and press the channel button (18) on the remote control to select “CONT. MAX”.
Press the VOL. UP/DOWN button on the remote control until the contrast step No. becomes “85”.
Receive a broadcast and check if the picture is normal.
Press the INPUT button on the remote control to set to the AV mode. Then perform the above adjustments 1~3.
Press the INPUT button on the remote control to set to the CS mode. Then perform the above adjustments 1~3.

OSD horizontal

Activate the adjustment mode display.
Press the VOL. UP/DOWN button on the remote control until the difference of A and B becomes minimum.

Confirmation of Fixed Value (step No.)

Check if the fixed values of the each adjustment items are set correctly referring below.