How To Restore A 17" Monitor CRT Image Tube
The first part of the article talked about about how you can tap from the secondary diode to get the need output by the 7808 voltage regulator. The weakness of this circuit is that it will probably't energy up the 17" Monitor as a result of the power provide have some limitation in delivering present to the larger CRT tube. The ability supply will either shut itself off or power blink. To be able to counter this problem, we've got to tap voltage from some other places in the Monitor. Sadly there were no more locations (level) within the Monitor the place you can faucet the voltage to power up the bigger CRT tube. Attributable to we couldn't find the purpose then we've got to create (design) our own circuit. The most effective is to use the Monitor flyback transformer ferrite core and with wire loop around the core will produce excessive pulse ac. This high pulse ac can't be measure by your normal meter.
With few turning at the core (external loop), you will get a higher ac output voltage to energy up the CRT heater. This technique only applies if you want to brighten up a Tv picture tube. You'll be able to't use this manner on Monitor CRT because as mentioned earlier within the first a part of the article, Monitor runs on totally different resolution. The higher the decision, the upper the B+ voltage provide to the primary winding of the flyback transformer. The higher the B+ voltage, the higher is the voltage output on the secondary aspect making the output voltage (ac) produced by the external loop even higher. Thus this can make a sudden enhance in the filament voltage inflicting an prompt brilliant within the Monitor raster. Some monitor designed will shutdown if it detect a sudden brightness in the raster.
Even when the monitor didn't shutdown and if the consumer determine to lower the Monitor decision, the raster will suddenly turn out to be too dim on account of decrease B+ voltage. You might ask your self why computer Monitor has its personal 6.three vdc output and why not like TV, the heater voltage comes from the secondary winding of TV flyback transformer? The reply is because the Monitor designer needs a steady 6.three volt for filament and don't desire the raster to be affected by a altering in Monitor resolution. So as to remedy this drawback, after making about 7 to 10 loops across the flyback transformer core, it's a must to convert this high pulse ac into DC voltage. You'll be able to't simply use any diodes for this purpose. A normal purpose diode like the well-known 1N5401-1N5408 would not be able to work in this circuit. The high pulse ac voltage will immediately kill the diode once the Monitor is switched "on". You must use an extremely quick restoration diode to do the job.
On your data, not all ultra quick recovery diode can efficiently run on this circuit. It's a must to select the diode type that has a faster velocity time like a 50 nanosecond and below. I had tried a seventy five nanosecond ultra quick restoration diode and it blown at 800 by 600 resolutions but work well within the 640 by 480 resolution. After performed some R & D, I found that the very best part number to make use of is the UF5404. This diode has the specification of 400V, 3A and 50ns. After you have related the ac voltage to the diode, you now have to make use of a filter capacitor to filter off the ripple. You should utilize a value of 220 to 1000 microfarad 50V. Measure the output DC voltage and make sure it must have about no less than 15 to twenty over volts before you solder to pin 1 of 7808 voltage regulatorYou can even attempt to use a 7809 if the show isn't bright enough. Do not use any voltage regulator that's increased than 7809 otherwise the heater filament will get too hot and burn.
Pin three of the voltage regulator is the output and it should joint to the heater pin at the CRT board as shown in the photo. Fastidiously place all of the wires in a strategic location and attach the voltage regulator at the warmth sink beside the flyback transformer. You are now ready to modify on the Monitor and examine if there's enchancment within the display. If it okay then burn in test the Monitor for couples of days to test if the display is still vibrant and clear. In case you are not glad with the sharpness, you possibly can try to improve one other volt by altering the voltage regulator half number to 7809. Some technicians prefer to make use of a variable voltage regulator such because the LM317T with a variable resistor in order that they will alter to the need voltage. If the picture tube continues to be dim and no way you could enhance the display, I guess the time is up for the CRT tube. You either substitute a used tube or return the Monitor again to the customer. I hope you take pleasure in studying this article. If that's the case, please be at liberty to share this article with your folks or simply forward this text to anybody you would like! There is no limit on the number of individuals you may share this with! You probably have a question or remark about something on this article, drop me an email. Your feedback is welcome!
How To Restore A 17" Monitor CRT Image Tube
The first part of the article talked about about how you can tap from the secondary diode to get the need output by the 7808 voltage regulator. The weakness of this circuit is that it will probably't energy up the 17" Monitor as a result of the power provide have some limitation in delivering present to the larger CRT tube. The ability supply will either shut itself off or power blink. To be able to counter this problem, we've got to tap voltage from some other places in the Monitor. Sadly there were no more locations (level) within the Monitor the place you can faucet the voltage to power up the bigger CRT tube. Attributable to we couldn't find the purpose then we've got to create (design) our own circuit. The most effective is to use the Monitor flyback transformer ferrite core and with wire loop around the core will produce excessive pulse ac. This high pulse ac can't be measure by your normal meter.
With few turning at the core (external loop), you will get a higher ac output voltage to energy up the CRT heater. This technique only applies if you want to brighten up a Tv picture tube. You'll be able to't use this manner on Monitor CRT because as mentioned earlier within the first a part of the article, Monitor runs on totally different resolution. The higher the decision, the upper the B+ voltage provide to the primary winding of the flyback transformer. The higher the B+ voltage, the higher is the voltage output on the secondary aspect making the output voltage (ac) produced by the external loop even higher. Thus this can make a sudden enhance in the filament voltage inflicting an prompt brilliant within the Monitor raster. Some monitor designed will shutdown if it detect a sudden brightness in the raster.
Even when the monitor didn't shutdown and if the consumer determine to lower the Monitor decision, the raster will suddenly turn out to be too dim on account of decrease B+ voltage. You might ask your self why computer Monitor has its personal 6.three vdc output and why not like TV, the heater voltage comes from the secondary winding of TV flyback transformer? The reply is because the Monitor designer needs a steady 6.three volt for filament and don't desire the raster to be affected by a altering in Monitor resolution. So as to remedy this drawback, after making about 7 to 10 loops across the flyback transformer core, it's a must to convert this high pulse ac into DC voltage. You'll be able to't simply use any diodes for this purpose. A normal purpose diode like the well-known 1N5401-1N5408 would not be able to work in this circuit. The high pulse ac voltage will immediately kill the diode once the Monitor is switched "on". You must use an extremely quick restoration diode to do the job.
On your data, not all ultra quick recovery diode can efficiently run on this circuit. It's a must to select the diode type that has a faster velocity time like a 50 nanosecond and below. I had tried a seventy five nanosecond ultra quick restoration diode and it blown at 800 by 600 resolutions but work well within the 640 by 480 resolution. After performed some R & D, I found that the very best part number to make use of is the UF5404. This diode has the specification of 400V, 3A and 50ns. After you have related the ac voltage to the diode, you now have to make use of a filter capacitor to filter off the ripple. You should utilize a value of 220 to 1000 microfarad 50V. Measure the output DC voltage and make sure it must have about no less than 15 to twenty over volts before you solder to pin 1 of 7808 voltage regulatorYou can even attempt to use a 7809 if the show isn't bright enough. Do not use any voltage regulator that's increased than 7809 otherwise the heater filament will get too hot and burn.
Pin three of the voltage regulator is the output and it should joint to the heater pin at the CRT board as shown in the photo. Fastidiously place all of the wires in a strategic location and attach the voltage regulator at the warmth sink beside the flyback transformer. You are now ready to modify on the Monitor and examine if there's enchancment within the display. If it okay then burn in test the Monitor for couples of days to test if the display is still vibrant and clear. In case you are not glad with the sharpness, you possibly can try to improve one other volt by altering the voltage regulator half number to 7809. Some technicians prefer to make use of a variable voltage regulator such because the LM317T with a variable resistor in order that they will alter to the need voltage. If the picture tube continues to be dim and no way you could enhance the display, I guess the time is up for the CRT tube. You either substitute a used tube or return the Monitor again to the customer. I hope you take pleasure in studying this article. If that's the case, please be at liberty to share this article with your folks or simply forward this text to anybody you would like! There is no limit on the number of individuals you may share this with! You probably have a question or remark about something on this article, drop me an email. Your feedback is welcome!
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