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Post by Espen Skog on Nov 21, 2009 9:35:54 GMT -5
Just wondering. I keep reading that I should re-use the LED that came with the DTV and use it as a regulator for the supplied 5v input. However -- I am feeding my DTV with plain 5v from the USB from a PC and have never had any problems with this.
Can someone let me know why this works nice -- and why I should keep the LED when both solutions seems to work fine.
Regs Espen
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Post by spiff on Nov 23, 2009 4:45:39 GMT -5
The LED is part of the regulator for 3.3V, used everywhere on the DTV board. Feeding the 3.3V regulator 5V is fine. Also, this provides a nice 5V, which can be used for a PS/2 keyboard and such.
If you remove the regulator circuit, some other way of providing 3.3V is needed. I would not recommend supplying 5V to the 3.3V circuit, as the parts are not rated for 5V operation.
Personally, I use a 5V regulated supply on the battery terminals. This is a very common way to do it, but you need to keep the LED in place.
Other option is to remove the regulator circuit and put in a new 3.3V regulator. A few people have been doing this, but the benefits are minimal.
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Post by racob on Nov 23, 2009 7:48:48 GMT -5
I just received a DTV2 (to hack) from UK and noticed the following: 1. That the negative wire is the one being switched. I was testing it (to combine) to a display unit so I used a common 5V from the host circuit..wired the neg (-) AND connected the composite out (both cvbs and gnd)...this is when I noticed that I cannot switch it off. I took out the GND wire from my Video out and is now OK. 2. Compared to the hummer (am I imagining?) but the Regulator seems HOT TER during operation. I am thinking of replacing it with a much higher rated regulator. 3. I read somewhere that the LED circuit drains whatever voltage is left when it is switched off.
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Post by Espen Skog on Nov 27, 2009 8:56:10 GMT -5
I now measured the ouputvoltage of the regulator circuit and it was 3,9v without the diode in place. I did this over C31 which is according to the 3,3v regulator schematic. Then I soldered a red diode with about 2 v forward voltage and there was still 3,9v output from the regulator. So my quiestion is: Can someone verify this ? To measure the output of the regulator on the DTV board, I hooked up my voltmeter to the pins as seen here: picobay.com/dtv_wiki/index.php?title=Image:Dtv2_power_circuit.pngSo my big question is: Why is the output 3,9v with and without the LED in place between "LED+" and "BAT-" Can someone measure the voltage drop over C31 for me where they have the LED in place ? I wonder if 3,9V to the DTV works okay-ish as it is close-enough to 3,3. Anyone ? Regs, Espen
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