VIDEO CIRCUIT

Video Distibution Amplifier with Five Outputs

noreply@blogger.com (Go2Media) — Thu, 16 Jul 2009 09:51:00 +0000

Video fans and professionals in the field will find in this small signal distributor-amplifier an excellent ally when it’s necessary to distribute a single video signal across several equipments. The circuit shown here should have a lot of applications.

Basically, the distribution amplifier takes the composite video signal from a video player (VCR) or a video generator (analogue output) and buffers it in such a way that it can be simultaneously applied to up to five different video equipment inputs, like monitors, TV sets, other VCRs and so on. For example, in a hall, the image produced by a central DVD player can be shown on five different TV screens with the sound reproduced through a separate amplifier.

The circuit is based on the type EL2020 (or similar) operational amplifier which is marled by large bandwidth. The LL2020 amplifies the video signal applied to the input stage, with a gain adjustment range of ±6 dB. Output transistor Q1, a 2N3866, applies the video signal to the five outputs designed to drive loads with 75-Ω impedance.

The circuit requires a ±12 V symmetrical supply voltage, which can be obtained from a conventional power supply as shown by the schematic.

S-video Converter Circuit

noreply@blogger.com (Go2Media) — Mon, 13 Jul 2009 03:20:00 +0000

With the astonishingly rapid growth in the market for flat-screen TVs and high-definition TV, many CRT television sets have been consigned to the attic, even though many of them were still working perfectly and could have been used as spare sets in a bedroom or another room, for example. Although all current flat-screen receivers have very comprehensive facilities and include digital inputs via DVI or HDMI connectors and analogue inputs in S-video format, this was unfortunately not the case with the CRT televisions that were being sold only a few short years ago, which were more often than not fitted with only composite video inputs, either directly or via their SCART socket.

The s-video converter we are suggesting building, very simple since it only uses two transistor, lets you convert any S-amplivideo signal into a composite signal and so will perhaps enable you to give a new lease of life to your old CRT television.

The principle of S-video is very simple, as it merely consists of carrying the chrominance and luminance information, which form the basis of all colour video signals, over separate channels. In composite video, by contrast, both these signals are combined over a single path, and the resulting inevitable interferences between them degrade the appearance of the image being reproduced. Fortunately, the components of an S-video signal, whether in the SECAM, PAL, or even NTSC standards, are almost the same as the ones found in a composite signal of the same standard.

So it’s going to be relatively simple to combine them in order to reconstitute the composite video signal that our CRT television is expecting to see. In order for this recombination to be correct, there is just one constraining factor to be taken into account, concerning the respective levels of the components, as the chrominance one is only half the amplitude of the luminance one.

Our circuit picks up the component signals on the two standardised pins of the 4-pin mini-DIN socket normally used for S-video (also known as an Ushiden socket), taking care to maintain the 75 Ω impedance via R1 and R2. The mixing of the two signals is then taken care of by R3, R4, and P1; the latter lets you adjust the respective levels of the two component signals exactly.

The two transistors that come next are wired in such a way as to create a wideband amplifier, the gain of which is set to 3 by t0he ratio between R8 and R9. Combining the input components has had the effect of dividing the overall amplitude of the video signal by a factor of 1.5, and the output impedance matching resistor is going to divide the signal in half again (once the signal is terminated at the input of the destination equipment), all of which adds up to a total attenuation of 2×1.5, corresponding to the make-up gain we have designed into our amplifier. In this way, inserting our converter into a video chain will have no effect on the level of the signals passing through it.

The composite video output passes via 75 Ω resistor R11 in order to match the circuit’s output impedance to the input impedance of the composite video input on the device to which it is connected. At both input and output, note the parallel combinations of C1 / C2 and C3 / C4, so that the video signals, with a frequency range extending from a few tens of Hz to several MHz, can pass through these capacitors under the best possible conditions.

If we want to avoid unwanted colour or brightness variations, it is vital to power the circuit from a stabilized supply, achieved here by using a standard 3-pin regulator IC to provide a 5 V rail for the circuit. So the project can be powered from a ‘plug-top’ mains unit that gives 9 to 12 V at 100 mA or so. Diode D1 is there just to protect against any accidental inversion of the PSU polarity that might possibly occur.

The circuit itself is very easy and construction shouldn’t present any difficulties. It can be built on the PCB we suggest [1] or on a piece of prototyping board, but in either case, we recommend using fibreglass board, because of the high frequencies involved in the video signals.

If you want your converter to follow the proper standard in terms of connectors, you’ll want to use a female 4-pin mini DIN S-video socket for the input and a female phono socket (a yellow one, for the purists!) for the output. As for the power supply, all you’ll need is a simple jack to suit the mains unit you’ve chosen.

The circuit should work right away, and all that you then have to do is to adjust the preset P1 so as to obtain a composite video signal that gives correct contrast and saturation on the TV receiver you are using. Author : Christian Tavernier (France), Elektor Magazine 2009

AM Video Modulator

noreply@blogger.com (Go2Media) — Wed, 21 Jan 2009 14:25:00 +0000

Here's the simple design allows ATV to be transmitted from a low-power (up to about 3W) FM or CW transmitter. Ideally the transmitter should use CW mode and have its 'key' down but an FM rig will work just as well if the microphone is disconnected and the PTT switch is closed. The only reason for disconnecting the microphone is to prevent sounds from it frequency modulating the carrier.

All the design does is interrupt the supply current to the power amplifier and possibly also the driver stage of the transmitter. It allows the depth of modulation to be set and the quiescent PA current. Setting the current is important because almost all small transmitters run their output stages flat out but for AM, the power needs to both decrease and increase above mean level.

As the unit only requires three connections to the transmitter, it can be mounted outside the rig if preferred. Connections A and B are the video input and should be fed through a screened 75R impedance cable. Connection C goes to the existing PA supply line and connection E goes to the PA stage(s). If SW1 is closed the rig essentially returns to its previous functionality. Connection D is the 0V ground to the negative side of the rig's supply.
Setting up is quite easy:

With the switch closed, make sure the rig behaves normally. Open the switch and check that adjusting RV2 makes the rig's output power vary. It should go from near normal down to almost nothing.

Apply a standard 1 Volt p-p video signal across A and B, a camera can be used if one is to hand. Start with RV1 set to mid-position and while monitoring on a TV receiver, adjust RV2 until a locked picture can be seen. Adjusting too far one way will cause the sync pulses to compress and the picture will tear or roll, going too far the other way will cause white areas to smear, looking rather like an over-exposed photograph. Set it half way between these points.

Now adjust RV1 for optimum contrast, you will find the controls interact slightly so it might be necessary to adjust RV2 again to clean the picture up. When set correctly a solid, fully contrasted picture should be seen.

AM Video Modulator Parts List:
R1 270R
R2 1K5
R3 820R
R4 82R
C1 10uF
C2 47pF
C3 220uF
C4 100nF
TR1 2N2222
TR2 BD131
VR1 100R
VR2 470R
D1 1N4148
SW1 see text
SW1 can be any single-pole switch capable of carrying the PA stage current, normally this is less than 1 Amp. TR2 will require a small heat sink, the PCB has room to fit one.

Note: If possible cut the existing PA supply feed AFTER any large (>470pF) decoupling or filter capacitors so they they are connected on the "C" side of the schematic rather than the "E" side.

Download PCB Files More AM Video Modulator

Video Mixer Using the GT4123 and GT4123A

noreply@blogger.com (Go2Media) — Wed, 21 Jan 2009 14:01:00 +0000

The GT4123 and GT4123A are the first dedicated single device, two input video mixer ICs available to the professional video and multimedia. Read more for description and circuit diagram.

A PC board which uses two GT4123 mixers, two GB4551 back-porch clamps and a GX4314, 4x1 video switch is available from GENNUM. This board can be used to gain experience in using these devices in a simple Effects Generator application.

Figure 5 shows the circuit of this board which contains the video signal paths but does not include the control circuitry needed to perform the various functions such as a KEY, WIPE, RAMP or FADE. These control signals are generated from other circuitry using standard logic gates, monostable multivibrators and comparators.

The two video signals (VIDEO 1 and VIDEO 2) are applied to the GB4551 back-porch clamps via 0.1 mF capacitors C1 and C2. These inputs must be suitably terminated with 75 W resistors. The VIDEO 2 signal must also be applied to a sync separator
circuit in order to produce a negative going back-porch pulse used by the GB4551s.

The clamped output from the first GB4551 feeds the V INA input (pin 5) of the first GT4123 mixer. It is also used to drive a comparator in order to produce a luminance key signal. The V INB input (pin 7) of this mixer is fed from the second GB4551.
Both of these clamped video signals are applied to inputs of the GX4314, 4x1 video switch.

By linearly varying the voltage on pin 3 of the GT4123, a smooth A/B mix can be achieved and a resultant signal appears at the output (pin 1). The voltage on pin 3 can also be controlled by a chroma or luminance key signal or by an appropriate horizontal or vertical wipe waveform.

The only restriction on the control signal is that the peak to peak amplitude should be 1 volt centred around 0.5 volts.

More detail Video Mixer Using the GT4123 and GT4123A

Video Signal Amplifier

noreply@blogger.com (Go2Media) — Sat, 25 Oct 2008 12:31:00 +0000

This electronic circuit is a video signal amplifier that offers a broad band amplifier with a bandwidth of 5 MHz which will take the video signals from your VCR and will amplify them sufficiently to drive up to 3 monitors, TV sets (provided that they can accept direct video signals), or other VCR's for recording from one video to up to three others.

The video signal amplifier will also make possible to record from one video to two others and at the same time have a monitor connected to check what you are recording. The amplifier is also very useful if the video recorder is far from the monitor.

The circuit needs a 12 VDC power supply and it is much better if it is a stabilised one like the circuit printed elsewhere in the instructions.

Video Signal Amplifier Construction

PIC16F84 Video Generator

noreply@blogger.com (Go2Media) — Thu, 09 Oct 2008 03:29:00 +0000

Here's the project was to construct a Composite Video Pattern Generator, which can be used as a teaching tool in the video field as well as a laboratory instrument, useful for repairing and adjusting television receptors.

This video generator instrument is in no way intended to be a commercial set, because I cannot guarantee all the specifications that a professional tool must have. However, the result is a high quality video equipment.

Download PIC16F84 Video Generator for ASM-HEX Code and Schematic

Sync-Tip Clamp/Restorer with AGC and De-Emphasis

noreply@blogger.com (Go2Media) — Wed, 24 Sep 2008 07:40:00 +0000

This video circuit is Sync-tip Clamp/Restorer with AGC and De-emphasis. The active component used IC MAX7450.

Below video clamp/restorer with layout and PCB

Source : http://www.g8ajn.tv/

Monitor Test Program

noreply@blogger.com (Go2Media) — Thu, 10 Jul 2008 17:14:00 +0000

The Monitor Test program is a Windows application which comes in the help of electronics technicians for adjusting computer monitors and for general users for testing the quality of their monitors.

It displays different patterns on the screen and it also allows to change the resolution from 640x480 to 1600x1200. These patterns are useful for checking or adjusting the convergency, focus, brightness, contrast, dynamic convergency, geometry and the overall quality of CRT monitors (CRT means cathode ray tube).

This software is provided AS IS and WITHOUT ANY WARRANTY! E-Leader doesn't assume the responsibility in any way for loss or damage of any kind resulting from the use of the program including, but not limited to, loss of goodwill, work stoppage, computer failure or malfunction, data loss, data corruption or any and all other commercial damages or losses.

Download the program: DOWNLOAD ZIP ARCHIVE

Source

Video-Based Motion Sensor

noreply@blogger.com (Go2Media) — Thu, 03 Jul 2008 16:45:00 +0000

The design is primarily based on an analog integrator circuit. The circuit integrates (i.e., sums) the input-voltage signal over a defined period of time. Based on an op-amp, the ideal circuit is shown in Figure 3. The factor –(1/RC) is constant, so the resulting output is inverted and proportional to the sum of the integrated values (i.e., proportional to the average of the signal in the integrated period of time). This is all it takes to “compress” the analog video signal.

Although it seems complicated at first sight, it should be fairly simple by now (see Figure 4). The integrator is implemented by a National Semiconductor LM6134B, a fast, rail-to-rail, single-power supply op-amp (U3). The output should then be quickly converted to digital because the input changes very fast. Analog Devices’s AD9280 ADC (U1) with 32 Msps was selected so a 50-ns capture could be performed. The AD9280 was configured for 1 to 2 V of input to use the internal 2-V reference. A 1-V reference was obtained with U3:D. To prepare the input for this range, the signal was inverted with the op-amp U3:A and clamped just less than 1 V with U3:B (see Figure 2). Just before the integration, the video was inverted under 1 V. The integrator was designed to output a 1-V signal when a ground-referenced, fully saturated video signal was input in 4.3-µs intervals. Note that the integrator is offset at 1 V. So, after signal integration, the ADC will receive a signal that is from 1 to 2 V as required. The integration capacitor C12 is a low-leakage metalized polyester film type. R8 is a metal film resistor, also a 1% part. To reset the integrator, a 74HC4066 analog switch (U4) is used. It is controlled by the ATmega88 through the INT_ENABLE signal.

The video frame start is detected through the INT0 interrupt when the odd/even output of U2 changes. By using the odd/even output instead of the vertical synchronization output, the same pin can be used to determine if it is an even or odd frame. The video-line start is detected using the composite synchronization output of U2, which is connected to the AVR’s INT1 input.

The video output block performs the video highlighting. It is a transistor-based video amplifier that increases the gain when its enable signal is asserted low. Highlighting is used to show where a movement has occurred in the previous frame. It also gives you feedback on the blocks that will be ignored while executing the masking commands.

The only digital components in the design are the ATmega88 (U5), which has 8 KB of flash memory and 1 KB of RAM, a 20-MHz clock, and an RS-232-level converter (U6). The ATmega88, with its versatile instruction set, was key to developing this project. The generous 32 registers, bit-manipulation instructions, and word-pointer registers allowed the integration algorithm to fit in 4.7 µs, where the next sample should be captured. The software was developed in assembler to achieve the large optimizations required. I used AVR Studio 4 as the developing and testing environment.

The circuit requires a regulated 5-V power supply for the analog and digital circuits. A single regulator can be used for both the analog and digital parts, provided that the signals are well filtered, and there is a single point of contact between the ground rails. Take a look at the motion-sensor prototype in Photo 2.

Source: Copyright Naubert Aparicio

Triple Video Buffer with Filter TSH173

noreply@blogger.com (Go2Media) — Sat, 28 Jun 2008 17:08:00 +0000

This Triple Video Buffer with filter is designed to aid in the evaluation of the TSH173, a single supply triple video buffer featuring an internal gain of 6 dB and an internal low pass filter with an 8.2 MHz cut-off frequency for each channel, in compliance with standard-definition requirements for video line interfaces.

Features

4.5 V to 5.5 V single supply operation
R-G-B, Y-Pb-Pr, Y-C-CVBS driving
3 channels with 6 dB gain buffer
3 video reconstruction filters for SD (standarddefinition)
3 internal input DC level shifter
Very low harmonic distortion
Each output (datasheet)

Video Buffer and Filter with SAG Correction Based on The TSH120

noreply@blogger.com (Go2Media) — Sat, 28 Jun 2008 16:41:00 +0000

This evaluation board Video Buffer and Filter circuit is based on the TSH120 video buffer. The TSH120 includes a voltage feedback amplifier with an internal gain of 6 dB, rail-to-rail output, internal input biasing and SAG correction. A power-down function provides a sleep mode with ultra low power consumption.

Features

Very low consumption in active and standby mode
Internal reconstruction filter
Internal gain of 6 dB
Rail-to-rail output
Operating supply voltage from +2.2 V to +5.5 V
SAG correction
Excellent video performance

Differential gain: 0.5 %
Differential phase: 0.5°

Group delay=10 ns
Specified for 150 Ω load
Input DC level shifter (datasheet)

Video Modulator Circuit TDA6800(T)

noreply@blogger.com (Go2Media) — Sun, 22 Jun 2008 14:58:00 +0000

The TDA6800 is a modulator circuit for modulation of video signals on a VHF/UHF carrier. The circuit requires a 5 V power supply and few external components for the negative modulation mode. For positive modulation an external clamp circuit is required. This circuit can be used as a general purpose modulator without additional external components.

Features
· Balanced modulator
· Symmetrical oscillator
· Video clamp circuit for negative modulation
· Frequency range 50 to 800 MHz

Output impedance 75 Ohm (datasheet)

The Difference Between a RF Modulator and Video Switcher

noreply@blogger.com (Go2Media) — Sun, 22 Jun 2008 14:43:00 +0000

RF modulators make it possible to connect devices to televisions where it would otherwise be impossible to. Video switchers make it possible to connect more than one device to the same input without the need for changing out the wires every time you want to switch equipment.

RF Modulators
RF modulators are useful devices for people who own televisions with RF/coaxial-only inputs because without the RF modulator there would be no way to connect a DVD player or video game console to the television. All RF modulators require an external power supply.

With rare exception, DVD players and video game consoles connect to televisions via S-video or composite video cables. They also require an additional audio connection, usually a RCA stereo cable. Obviously, these types of connections are not possible on a television that only supports a coaxial cable. When plugging these devices into a RF modulator, the end result is a conversion of the S-Video or composite and audio signal into one RF signal, which means your DVD player and video game console will now work on your RF-only television.

Video Switchers
A video switcher is a great product for people who own a television that has only one composite video or S-Video input, but want to connect more than one device to it. Usually, people without a video switcher would have to disconnect one device and connect the other to get use of the device of choice.

But, those owning a video switcher could plug both devices into the video switcher, which would then plug into the television. The video switcher has buttons on the front that are married to the connection ports on the back. By plugging both devices into the video switcher, a person would only have to press a button to open the signal path for the device of choice.

This is a great tool for people who own a products like a DVD player, video game console and digital camcorder. Most video switchers are passive, which means they don't require external power. From Matthew Torres

AM Video Modulator

noreply@blogger.com (Go2Media) — Sun, 22 Jun 2008 14:21:00 +0000

The first section of the video modulator performs a video level clamping function. The high input impedance Darlington amplifier and the small series coupling capacitor combine to achieve an excellent low-frequency response and a clamping function with very rapid response time. A three terminal voltage regulator sets the clamping level to 8 volts.

The clamped video is then level shifted through a zener diode and applied to a single video amplifier stage. A PNP transistor in the collector circuit functions as a constant current source for the video amplifier. The use of a constant current source rather than a collector load resistor in the video amplifier results in very high voltage gain with nearly rail-to-rail output voltage capability. Negative feedback around the video amplifier reduces the gain to the amount required, while it increases the bandwidth, flattens the frequency response, increases the linearity, and reduces any distortion products to extremely low levels.

A 2N3904 in the base circuit sets the `Q' point of the amplifier. FM subcarrier audio at 4.5 MHz is also injected at this point through a 3300 ohm resistor and a DC blocking capacitor. A high frequency 5-watt RF power transistor (2SC1909) serves as the last stage of the modulator. An NTE-235, NTE-236, or equivalent is suitable in this application.

Clamped video is also fed into an LM311 voltage comparator that serves as a video sync detector. Some builders have used an LM1881 sync separator chip for this stage. Either way, sync pulses detected by this circuit trigger a CD4016B silicon bilateral switch that lowers the negative feedback around the video amplifier and voltage follower at sync time to compensate for high power gain compression in any solid-state linear power amplifiers that may follow the video modulated stages. This method of sync expansion is unique in that it also compensates for audio subcarrier compression at sync time, resulting in a clean output signal with no sync buzz in the transmitted audio.

R1 is a video gain control. It is used to set the white modulation level. R2 is a video bias control. It is used to set the black modulation level. R3 is adjusted so that the LM311 delivers clean sync pulses to the CD4016B with an input signal present. R4 adjusts the sync modulation level. Up to 9 dB of sync expansion is possible with this circuit.

Video Modulator Performance
The following graphs show the results of a computer simulation of the video modulator when adjusted for a voltage gain of 20 dB. This simulation was performed using MicroCAP IV software, an electronic circuit analysis program by Spectrum Software.

Conclusion
Feedback received from others who have duplicated this modulator and used it in their own ATV transmitters and repeaters confirm its excellent performance. This modulator has also been used in a completely new exciter that has recently replaced the PC Electronics exciter originally used in the Brookdale ATV Repeater System.

Source: http://www.qsl.net/kd2bd/modulator.html

Video Amplifier with Sync Stripper and DC Restore EL8102

noreply@blogger.com (Go2Media) — Tue, 17 Jun 2008 05:31:00 +0000

The circuit transmits 200MHz (-3dB bandwidth) video signals while stripping off the sync pulse and performing DC restoration. It is configured for a typical video cable driver application driving a double-terminated 75Ω load, where the EL8102 (IC3) is configured for a gain of +2 to ensure unity gain throughout.

Sync Stripping
In component video systems it is frequently necessary to remove the sync pulse from an RGB signal. Sync is often combined with one or more of the red, green, and blue video signals in video distribution amplifiers, routers and switchers to decrease the number of input and output channels required in a switching network. In many applications, however, as the video signals exit the switching network the sync pulse must be removed.
The EL8102 video op amp is specially designed to perform sync stripping. Its open emitter NPN output forms an emitter-follower with the load resistor, and passes the active video signal while virtually eliminating the negative sync pulse (see Figure 2). Residual sync of the EL8102, defined as the remainder of the original -300mV sync pulse, referenced to ground, is only 8mV at the cable output. A particular advantage of sync stripping with the EL8102 is the resultant larger (by 0.7V) output voltage swing, compared to simply using a wideband video op amp with an external emitter-follower.

Because the EL8102 contains no active pull-down, output linearity degrades as the signal approaches ground. To deal with this a 6.8kΩ pull-up resistor (R8) and a 75Ω pull down resistor (R10) on the output ensure a fixed positive voltage offset, in this case +50mV. This offset was arbitrarily chosen as a good compromise between linearity near the DC level and minimum residual sync. Increasing R8 decreases residual sync, at the expense of linearity. Conversely, decreasing R8 decreases linearity error, but increases residual sync.Other applications benefitting from sync removal are HDTV systems and video digitizing circuits. Consider a typical 1VP-P RGB video signal with a -300mV sync pulse and +700mV video data. By stripping off the unwanted sync pulse and digitizing only the active video, designers can use the full dynamic range of the A/D converter for the +700mV video data. This results in a 30% increase in resolution using the same A/D converter.

DC Restore
Another common video function is DC restoration, used when AC coupled signals have lost their DC reference and must have it periodically reset in order to retain brightness information.
This circuit accomplishes DC restoration using a CA5260 dual op amp (IC1a, IC1b) coupled with a sample-and-hold circuit based on the 74HC4053 switch (IC2). VIN, consisting of the input video signal and a DC offset (VDC), is routed to the non-inverting input of the EL8102 (IC3). The EL8102 is configured in a gain of +2 (to compensate for the attenuation resulting from double terminating the cable), which would result in an output of 2 x VIN. (datasheet)

Video Amplifier LH0032

noreply@blogger.com (Go2Media) — Tue, 17 Jun 2008 05:04:00 +0000

This electronic circuit is Video Amplifier Application using Integrated Circuit (IC) LH0032, High Speed Op Amp Applications.

Circuit Schematic

Typical Response

Part List
R1= 15Kohm+15Kohm
R12= 100ohm trimmer
C3=4.7pF ceramic
R2-3-4= 10Kohm
R13-15= 47ohm
IC1= LH0032 (datasheet)
R5.....9= 1Kohm
R14= 10Kohm
S1= 1X2 mini switch
R10= 820ohm
C1= 10uF 63V MKT
S2= 1X6 sel.
R11= 1Mohm
C2-4= 100nF 63V
J1-2= BNC connector

Connecting your Computer to a Television

noreply@blogger.com (Go2Media) — Sun, 15 Jun 2008 14:15:00 +0000

It is a nasty surprise when you switch your monitor on and nothing appears on screen after a patient wait. Even though the resolution is much low, a television may help you to conduct basic procedures (copying your files for example) in such an emergency. You may think that this is only possible through expensive VGA cards but it's not true. A simple circuit can combine the VGA synchronization signals into composite TV synchronization signal. Following circuit by Tomi Engdahl carries out this job successfully without any problems. It utilizes a TTL IC, two transistors and a few resistors.

By putting all of the components on a PCB makes it easier to prepare a portable VGA to TV adapter. You'll need a male VGA connector to be connected to your PC and a Scart connector for your TV. Six lines of cable goes from VGA Card to TV without any alteration, only three of them is needed to be connected to the PCB board. Here is a PCB design I suggest using.

You'll need VGA connector's and Scart's pinouts also, so here they are.

Pinouts for VGA Connector

Pinouts for SCART Connector

Since circuit does not utilizes high currents, a very thin PCB plate would be enough. After drawing and etching processes, drill the holes and solder the components. Attach wires to the proper connection points and apply +5V supply voltage. If there's nothing wrong, you should measure nearly 75 mA current drag for a 74LS86 low power Schottky TTL type IC and again nearly 100 mA current drag for a 74S86 type IC.

Since sweeping frequencies of the VGA boards are higher than the TV's, a software is needed to alter it. Here is one called Television Eyes which both enables you to use circuit in DOS and Microsoft Windows (at 640 x 480 resolution). Just start your PC in DOS mode and run 'te.com' to install it as a TSR. If you press ALT - Left SHIFT - E keys simultaneously, the sweeping frequency of the VGA board will be changed and your TV will be able to sync the signal it receives.

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noreply@blogger.com (Go2Media) — Tue, 10 Jun 2008 12:11:00 +0000

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