Wiring & diagram Info: tv

Monday, November 17, 2014

TV Vertical Protectors

Vertical Protectors (another term surge protector or Vertical CRT Neck Guard or protector) . If the vertical deflection does not work, then the raster will glow a horizontal line. This can cause the picture tube phosphor layer was destroyed by fire when the aircraft be kept alive in the long term.

There are several types of system protectors, vertical relationships:

Protector surge protector is connected with x-ray to the horizontal which will trigger the horizontal oscillator is not working
Protectors gets connected to microcontrol that will trigger the "power off" so that the plane will turn off automatically or plane alive but raster becomes dark (brightnes level down).

Vertical Protect

The workings of the system-vertical surge protector that can be found there are several kinds:

Using sampling pulses from vertical-out IC which is connected to microcontrol . If microcontrol not receive these pulses the surge protector will work.
Using a sampling of the voltage supply Vcc-vertical IC connected to the IC microcontrol using a diode. In the normal kondidi no voltage on the pin-IC microcontrol protection. If the supply voltage Vcc or a short break then the voltage on the pin-microcontrol protection will come short to ground through the diode and trigger protection to actively work
Using the IC supply current sampling vertical-out that will actively work if the current exceeds supply. As the sensor protector installed here a series resistor and a transistor in the supply line where it works similar to the OCP.

Problems or possibilities that may cause the protector of vertically-active work:

Vertical IC-out short (broken)
No voltage supply to the vertical IC-out.
Vertical lines of the IC pulse-out to any part microcontrol broken or damaged
Vertical deflection section does not work (damage to the IC)

Thursday, November 13, 2014

VHF UHF TV Modulator

The electronic circuit is a TV modulator that is really no more than a transmitter. It is a very small transmitter, admittedly, but none the less that is what it is. What does a modulator actually do? In general -and this design is no exception to the rule - it is a simple oscillator that generates a frequency somewhere in the VHF or UHF region. The oscillator is modulated with the video signal and the modulated carrier wave thus generated is fed into the TV sets aerial input via a cable. Then all that remains to do is tune the TV to the correct frequency.

Circuit Schematic
The crystal oscillator is based on a very fast HF transistor, Tl (BFR91), which performs the amplitude modulation. Apart from this there is little to be said about the oscillator except, perhaps, that it is essential to use the correct values for the components surrounding Tl. This is, of course, simply common sense in this sort of HF circuit.

The harmonics generator is formed by two Schottky diodes, Dl and D2. These diodes must switch very quickly in time with the 27 MHz signal so they provide strong harmonics up into the gigahertz range. The modulation depth can be set with Pl, while the oscillators d.c. value can be varied by means of P2. The combination of these two presets enables either positive or negative amplitude modulation to be selected.

This is essential as the harmonics produced vary in this respect. We will discuss the calibration of Pl and P2 later in this article. The power for the circuit can be provided by either an unstabilized 8...30 V or a stabilized 5 V. The latter could be taken from a computers power supply and in this case ICI is not needed.

The printed circuit board for the modulator is only single-sided. The largecopper surface acts as a ground plain.

Parts list
Resistors:
R1, R2 = 4k7
R3, R4 = 56ohm
P1 = 100 ohm preset
P2 = 500 ohm preset
Capacitors:
C1 = 4mf7/16 V
C2= 10p
C3 = 220p
C4 = 47p
C5 = 47n, ceramic
C6 = 100n*
C7 = 330n*
Inductors:
L1, L2 = 3.5 turns of 0.2 mm (SWG 35 or 36) CuL on a ferrite bead of about 3.5 x 3.5 mm
L3 = 1 microH
L4 = 1 turn of 0.8. . .1 mm (SWG 19...21) CuL, air wound with a diameter of 8 mm
Semiconductors:
D1, D2 = 1N6263 (Ambit/Cirkit)
D3 = lN4148
T1 = BFR91 (Ambit/Cirkit)
IC1 = 7805*
Miscellaneous:
X1 = crystal, 27 MHzd(3rd overtone) or other 3rd overtone crystal between 25 and 30 MHz

*= not needed if the circuit is powered from a stabilised 5 V supply

Sunday, September 14, 2014

Video IF circuit TV

Video IF circuit

The main function of the video IF is to change the 38.0 MHz IF signal into the CVBS signal which later fed into the sound and video to the chroma.

VIF section consists of a series as follows:

IF amplifier

This section serves to strengthen the signal until the signal level is required. IF amplifier is equipped with AGC (Automatic Gain Controller) which controls the strengthening of the IF amplifier so that a constant amplitude output video. Amplifier frequency range from 32 ~ 60 MHz makes this amplifier suitable for applications multistandar.

PLL demodulator and VCO (voltage control oscillator)

IF signal is separated with the help of PLL detector. PLL detector produces a phase reference signal with the IF signal carrier and about 60 KHz bandwidth is determined by PLL loopfilter pin 37. Obtained by comparing the frequency demodulation reference signal with the incoming IF signal. Are required reference frequency (38.0 MHz) generated by the VCO. Appropriate VCO frequency is determined by system calibration using the crystal as a reference. PLL can detect the IF frequency up to ± 1 MHz based on FPLL (Frequency Phase Lock Loop System) which will provide an output signal to the PLL loopfilter for the difference frequency is obtained. If the phase IF signal with a reference signal, the signal is transmitted to the demodulator. Demodulator to control the positive and negative modulation, the selection made by the IIC bus. Low pass filter after the output signal demodulator eliminates the demodulation is not required to process the video.

Video Buffer

Video buffer to produce a video output with an amplitude of the right and keep the video output from the noise peak occurring. The bandwidth of the video buffer at least 6 MHz. In the video there are White spot clamp buffer (for positive modulation) and the noise inverter Clamp (for negative modulation) which keeps the amplitude of the video does not exceed the typical price.

Saturday, September 13, 2014

Simple TV Transmitter circuit diagram VHF

Most of people ask TV transmitters.So Today Im going to give you a very useful schema diagram.By using this schema you can send your signals 75m to 100m.This schema diagram is not my own schema one of my friends gave me this.I suppose you guys also can send your own schema diagrams for us.Then we can publish them through our website.Here They have used common transistor BC 108 If you are unable to find this transistor you can use equal transistors like Bc337 2n2222 Bc 546

Note

# To make L1 wound 6 turns of #24 enameled wire on a 10mm air former for frequency 60 - 80 MHz For 150 - 180 MHz wound 4 turns and for 180 - 200MHz wound 2 turns.

# This schema operates with 9V power supply

# When you build this schema you have to build this on a little space.

# The power of this schema is 80mW

# use a pcb to build this schema diagram.

# This is only for educational purpose.We can bear any responsibility of this If you misused this.

# This schema transmit only video signals .If you want to send sound signals you can use an audio transmitter

Thursday, August 7, 2014

TV Transmitter circuit diagram VHF

Most of people ask TV transmitters.So Today Im going to give you a very useful circuit diagram.By using this circuit you can send your signals 75m to 100m.This circuit diagram is not my own circuit one of my friends gave me this.I suppose you guys also can send your own circuit diagrams for us.Then we can publish them through our website.Here They have used common transistor BC 108 If you are unable to find this transistor you can use equal transistors like Bc337 2n2222 Bc 546

Note

# To make L1 wound 6 turns of #24 enameled wire on a 10mm air former for frequency 60 - 80 MHz For 150 - 180 MHz wound 4 turns and for 180 - 200MHz wound 2 turns.

# This circuit operates with 9V power supply

# When you build this circuit you have to build this on a little space.

# The power of this circuit is 80mW

# use a pcb to build this circuit diagram.

# This is only for educational purpose.We can bear any responsibility of this If you misused this.

# This circuit transmit only video signals .If you want to send sound signals you can use an audio transmitter