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A curious low voltage problem

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A curious low voltage problem

Postby zimjam » Sun May 06, 2012 2:19 am

Hello fellow EZ'ers =)

I am new here and I thought I would say Hello, and also present a problem I am facing.

So a big hello! I look forward to reviewing the site in depth and who know's I may even be able to help =)

Now onto this curious problem

I am building a Video SCART cable - absolutely nothing clever going on here - however for the RGB selection source it requires a voltage between 1 and 3 volts. The device being connected via SCART has 12volts output - however before the output the device has an inline 1Kohm resistor - this resticts the +12v from the coupling end to 0.84 volts when connected to the TV set - Sadly 0.84 volts happens to be just under the threshold of the required 1volt - and it would seem the tollerance of my TV.

So I need a way to increase the voltage upto atleast 1volt - without changing the device - only by adding / modifying the SCART cable.

here is what I have

+12v
Ground
Audio Out (200mV pk-pk)
Composite Sync (0.48v)
Red (1.6v)
Green (1.6v)
Blue (1.6v)

As mentioned before the +12v output has a 1Kohm inline resistor before the video connector. By running the 12v straight into Pin 16 of the Video Input Selection Source - I only get 0.84volts - which is a just under the tollerance of the minimum 1volt required to select RGB input.

The Red, Green and Blue signals are connected to the SCART with an inline 330 Ohm Resistor to bring the SCART input within the 0.7vpp tollerance (in fact its 0.67vpp)

So is there a way by say adding a capactior or other discrete that could negate some of that internal 1Kohm resistance of the +12v from the motherboard?

Thanks for reading.
zimjam
 
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Joined: Sun May 06, 2012 1:49 am

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