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oxxyfx

Max 4217

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Hello,

I have the MAX4217 in a circuit as shown in the picture below. The Video In is coming from an Airvawe receiver, and verified right at the input pins there is video signal, however on the output the video is black. What is the problem?

Thanks,

post-6-1182611206_thumb.jpg

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I also tried to disconnect the 75 ohm resistors from the outputs and connect them in series with the output, that is black video as well.

What am I doing wrong?

Thanks,

Ox

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Begin with this list.

1. Delete the A/C coupling cap (C3) on the input.

2. Install the two 75 ohm output resistors (R4,R5) in-series with the output signal (not as shown).

3. In addition to the 75 ohm output resistors, install two 470uF caps in-series with them too. The Plus side towards the MAX chip.

4. Go back and verify all other connections. Have a new set of eyes check it for you.

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With C3 you're getting rid of the RX's DC bias. But your amp requires it, because otherwise it will receive a negative voltage on the input. It can't handle that with only a positive supply. That's why you put the caps on the outputs :)

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Thank you. So if I compiled all what I read correctly then the schematics should be like the picture below.

Is this correct?

Thanks, Ox.

post-6-1182622183_thumb.jpg

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Looks correct to me. Don't forget the usual bypass caps on the IC's power leads (see page 9 of the data sheet).

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