Various diagram: tv

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Thursday, November 6, 2014

TV Muter Circuit

Many households are still graced by tube-type television sets. If you want to connect one of these large tellies to your stereo system to improve the sound quality, this is usually not a problem because there are plenty of SCART to Cinch adapters available in accessory shops. However, with some sets your pleasure is spoiled by the fact that the audio outputs of the SCART connector are not muted during channel switching. This can sometimes lead to nasty signal spikes, which can cause the loudspeakers of your stereo system to emit irritating popping and cracking noises. In such cases it is a good idea to fit your system with a mute circuit.

Fortunately, the right time to activate the mute circuit is defined by the fact that the happy zapper presses buttons on the remote control to switch channels, and the remote control emits IR signals. There are even inexpensive ready-made IR receiver modules available, such as the TSOP1136 used here, which produce trains of active-low pulses in response to such signals. About the circuit: when no IR signal is present, a capacitor is charged via P2 and a diode. IC1 is a comparator that compares this IR voltage (applied to its non-inverting input on pin 3) to a voltage applied to its other input on pin 2.

TV Muter Circuit diagram :

This reference voltage, which can be adjusted with P1, determines the switching threshold of the comparator. If IC2 receives an IR signal, T2 conducts, and as a result the voltage on C1 drops rapidly below the threshold level set by P1. This causes T1 to change from its previous ‘on’ state to the ‘off’ state. As a result, the relay drops out and the audio link to the stereo system is interrupted for the duration of the noise interval. It’s all quite simple, as you can see. If you do not have a stabilized 5-V supply voltage available, you can use the circuit at the of the schematic diagram (with a 5-V voltage regulator) together with a simple (unstabilised) AC mains adapter that supplies a voltage in the range of 9 V to 12 V to the 7805 (IC3).

You can also use a relay with normally-closed contacts instead of normally-open contacts. In this case, simply swap the signals on pins 2 and 3 of IC1 so the relay pulls in when an IR signal is received instead of dropping out. This saves a bit of power because the relay is only energized during zapping. If you can’t find any worthwhile use for the second comparator of IC1, it’s a good idea to connect pin 6 to +5 V and pin 5 to ground. To improve noise immunity, you should shield the IR sensor so it is not exposed directly to light from a fluorescent fixture.

Tuesday, November 4, 2014

VGA to TV Converter Circuit

This converter circuit basically takes VGA signals and converts it to RGB + composite sync signal which can be fed to TV via SCART connector. VGA card picture components RED, GREEN and BLUE are already at the correct voltage level (0.7Vpp) and has correct impedance (75 ohm) for direct connection to correspondign inputs in the TV.

VGA to TV Converter Ciruit

VGA to TV Converter Printed Circuit Board (PCB)

For combining separate horizonal and vertical sync signal from VGA card to one composite sync signal needs a sync signal conversion which is feed to TV video in pin in SCART connector. The tv converter circuit has also sends correct level signal to the TV RGB input enabling control pin in the SCART connector (pin 16).

The circuit is simply based on one TTL chip with four XOR ports, two resistors and two capacitors. TTL chip was logical choise because VGA sync signals are TTL level signals.

The sync signal combiner has a system to adjust to different sync polarities so that it always makes correct composite sync signals. VGA card uses different sync signal polarities to tell the monitor which resolution is used. This circuit adjusts to sync signal polarity changes in less than 200 milliseconds, which is faster than setting time of a normal VGA monitor in the display mode change. The tv converter circuit needs well regulates +5V (+/-5%) power supply and takes about 120 mA current.

VGA to TV converter parts list are as follow:

Main circuit

U1 74LS86 (74HC86 or 74HCT86 can also be used)

C1 22 microfarads 16V electrolytic capacitor

C2 use 47 uF 16V electrolytic for more reliable operation (22 uF listed schematic can cause problems in some cases)

R1,R2 2.2 kohm, 1/4 W

R3,R4,R5 2.2 kohm, 1/4 W

R6,R7,R9 47 ohm, 1/2 W

R8 120 ohm, 1/2 W

T1,T2 BC547B (2N2222 should also work but note the different pinout)

P1 15 pin SUB-D connector (DE-15)

Output connector

21 pin EURO/SCART connector

Wiring:

Red, Green, Blue and Composite Sync lines should be wired using 75 ohm coaxial cable for best picture quality, but can be replaced with normal shielded wire.

Power supply components

7805 regulator chip

100 uF electrolytic 25V

10 uF electrolytic 16V

100 nF polyester or ceramic condensator

Wall adapter which outputs 8-18V DC and 150 mA or more current

Connector for connecting wall adaptor to circuit

Monday, October 20, 2014

TV Relative Signal Strength Meter

This circuit was designed to assist the installation of TV antennas. The signal is monitored using a small portable TV set and this circuit monitors the output of the TVs FM detector IC via a shielded lead. To initially calibrate the meter, adjust trimpot VR2 to zero the meter. Trimpot VR1 is a sensitivity control and can be set for a preset reading (ie, 0dB) or can be calibrated in millivolts. Rotating the antenna for a minimum reading on the meter (indicating FM quieting) gives the optimum orientation for the antenna.

Circuit diagram:

TV Relative Signal Strength Meter Circuit Diagram

Monday, September 15, 2014

HP LCD TV LT3700 LT4700 LED BLINKING CODES HOTEL MODE PANEL FAULTS

HP LT3200, LT3700, LT4200, LT4700 High-Definition LCD TV - LED Blinking Codes & Panel Faults - Hotel Mode _ Software version

LED indicators

Special condition to watch out for with the following message: Red LED blinking 2 sec interval – Digital Demodulator does not respond.

Error code 003 (digital demodulator does not respond) requires source to be selected as “antenna” before the test is valid. If source is not antenna, it will always give you error code 003 because digital demodulator is not turned on until “antenna” source is selected.

Software version information.

To access the software version information OSD:

1 Turn the TV on.

2 Press the Menu button.

3 From OSD, select Setup => Time.

4 Press the following keys: SAP/MTS => 7 => 7 => 7. The software version information displays on the lower right corner of the TV.

To run diagnostics

1 Power off the TV and pull disconnect the power cord.

2 Plug in the power cord while holding the power button on the TV (not▲on the remote). Hold the power button until a testing message appears. This may take up to 30 seconds.

3 Diagnostic tests begin.

To get back to normal TV operation after running diagnostics

1 After the diagnostic test finishes, power off the TV and disconnect the power cord.

2 Wait for about 30 seconds; and then plug the power cord back in. The TV returns to normal mode.

Installation menu

The installation menu allows you to change default setting values of current input audio and video modes. For example, to change the picture settings for a component input, switch the TV source to component before entering this mode.

To access the Installation menu:

1 Turn the TV on.

2 On the remote, press the Menu button.

3 From the OSD, select Setup => Time.

4 If the TV is NOT in Hotel mode, press the following key sequences: SAP/MTS => 1 => 3 => 5.

5 If the TV is in Hotel mode, change input source to AV2, then press SOURCE=> 1 => 3 => 5.

Color adjustments in this menu apply to ALL modes (Cool, Standard, or Warm). If you want to adjust the color temperature of a single mode, you will need to adjust the White Balance settings in the Factory Menu.

Hotel mode

To access the installation menu:

1 Run the Setup wizard (or channel scan and time setup) through the main menu.

2 Access the install menu and change to HOTEL mode from Normal TV mode.

To access the installation menu:

1 Turn the TV on.

2 On the remote, press the Menu button.

3 From the OSD, select Setup => Time.

4 Press the following key sequences: SAP/MTS => 1 => 3 => 5.

To return to normal mode from Hotel mode:

1 On the remote, press the Menu button.

2 From the OSD, select Setup => Time.

3 Change input source to AV2, and then press SOURCE => 1 => 3 => 5.

Panel faults

Problem: Line

Solution: Change LCD panel.

Problem: Scrape on the LCD panel

Solution: Change LCD panel or change Polarizer

Problem: Mura (cloudiness)

Solution: Change LCD panel

Problem: LCD crack

Solution: Change LCD panel

Problem: Scrape on the LCD panel

Solution: Change LCD panel

Saturday, August 23, 2014

Solving the problem on tv tuner

Tv tuner serves as the catcher signals from the antenna. Damage tuner, among others:

1. Image does not exist and there is no sound, raster speckled thick.

2. No picture no sound, or otherwise.

3. Channel switching the channel itself.

4. Image blocking white or blue.

How to check the tuner and the IF is to remove the tuner from the PCB and connected by cable to the IF path, BM and Ground, then prepared using the pin on the tuner. Then the television was turned on, the antenna is connected to the antenna socket, and RV or potensio rotated slowly to choose the television channel when the tuner is in normal condition, the signal from the antenna to be acceptable, the picture and sound, and the channels do not move themselves. To damage its own channel switch and checked the normal manner stated above, the location of damage on the section of the program.

Monday, August 11, 2014

TV Relative Signal Strength Meter

This schema was designed to assist the installation of TV antennas. The signal is monitored using a small portable TV set and this schema monitors the output of the TVs FM detector IC via a shielded lead. To initially calibrate the meter, adjust trimpot VR2 to zero the meter. Trimpot VR1 is a sensitivity control and can be set for a preset reading (ie, 0dB) or can be calibrated in millivolts. Rotating the antenna for a minimum reading on the meter (indicating FM quieting) gives the optimum orientation for the antenna.

Circuit diagram:

tv-relative-signal-strength-meter-schema diagram1

TV Relative Signal Strength Meter Circuit Diagram