The primary a part of this text is about tips on how to contact the secondary diode to get the craving by the 7808 Voltage Regulator. "monitor as a result of the ability provide has some limitations on the ability provide of the bigger CRT pipe. The facility provide will both flip off or blink. So as to overcome this downside, we should contact the voltage on different places within the Monitor. Sadly, there aren’t any extra locations (factors) within the monitor the place you may contact the voltage to activate the bigger CRT tube. Since we couldn’t discover the purpose, we have to create (design) your personal circuit. It’s best to make use of the Monitor flyback transformer to make use of ferrite core and the wire loop across the core ends in a excessive pulse present. This excessive pulse AC cannot be measured utilizing the usual meter.
On the central unit (exterior loop) at some flip, the output voltage is larger for CRT heating. This methodology applies solely if you wish to scan a tv image tube. This mode cannot be used on Monitor CRT as a result of, as talked about within the first a part of this text, the monitor operates at completely different resolutions. The upper the decision, the upper the B + voltage provide to the first winding of the flyback transformer. The upper the B + voltage, the upper the secondary output voltage, which will increase the output voltage (ac) generated by the exterior loop even larger. So out of the blue the incandescent lamp rises, leading to fast lighting within the Monitor raster. Some screens are scheduled to cease should you discover the sudden brightness within the raster.
Even when the monitor doesn’t cease and if the consumer decides to cut back the monitor's decision, the raster out of the blue drops an excessive amount of, B + voltage. You would possibly ask your self why the monitor's personal 6.three Vdc output on the pc and why it doesn’t resemble the TV, is the heating voltage coming from the secondary winding of the TV flyback transformer? The reply is as a result of the Monitor designer needs 6.3V for the filament and doesn’t need the raster to have an effect on the Monitor decision. To unravel this downside, after we now have made round 7 to 10 loops across the flyback transformer core, we have to convert this excessive pulse AC DC voltage. For this function, you merely cannot use diodes. A basic function diode, such because the well-known 1N5401-1N5408, couldn’t function on this circuit. The excessive pulse voltage voltage instantly kills the diode after the monitor is switched on. Use an extremely quick reset diode to carry out this process.
Not all your extremely quick reset diodes can effectively run on this circuit to your data. It’s important to select the kind of diode that has a sooner velocity than a 50 nanosecond and under it. I attempted a 75 nanometer ultra-fast restoration diode and blew 800 at 800, but it surely works effectively at 640 and 480. After ending some R & D, I discovered that the very best half quantity is the UF5404. This diode has the 400V, 3A and 50ns specs. After connecting the AC voltage to the diode, you must now use a filter capacitor to filter the ripple. You should utilize the 220-1000 microfarad 50V. Measure the output DC voltage and guarantee that it have to be no less than 15-20 above the supply earlier than solder of the 7808 voltage regulator terminal 1. It’s also possible to strive utilizing 7809 if the show shouldn’t be clear sufficient. Don’t use a voltage regulator that’s larger than 7809, in any other case the heater is just too sizzling and sizzling.
Voltage regulator terminal three is the output and have to be linked to the heater on the CRT board as proven. Rigorously place the wires in a strategic location and join the voltage regulator to the warmth sink on the flyback transformer. You are actually able to activate the monitor and test if there may be any enchancment on the show. If that is superb, enter Monitor for each day pairs to ensure the show continues to be clear and clear. If you’re not happy with the sharpness, you may attempt to improve one other voltage by altering the voltage regulator part to 7809. Some technicians desire a variable voltage regulator, eg. The LM317T is used with variable resistors to regulate the need voltage. If the tube tube continues to be blurry and cannot enhance the show in any manner, I suppose time goes to the CRT tube. Exchange the tube you might be utilizing or convey the monitor again to the shopper. I hope you want studying this text. In that case, please share this text with your mates or just ahead this text to anybody you need! There isn’t any restrict to how many individuals you may share this. When you have any questions or feedback about something on this article, please ship me an e-mail. Your suggestions is welcome!
Supply by Jestine Yong