[Coco] Barry Nelsons SCART to HDMI (again)

[Barry Nelson]

> Paulo Garcia
> Thu Mar 1 23:00:34 EST 2018
> >From one of the comments in the hackaday page, it was mentioned that the
> PIN 16 should measure around 3V, but mine shows 5V.
> 
> The only difference I have is that I am using a 100ogm 1/2 watt resistor
> instead of the 1/4 watt, but as far I can understand that is only related
> to the amount of current the resistor can take, so using a 1/2 doesn't make
> any difference.
> 
> I wonder if someone can explain to me how the pin 16 gets 3V instead of the
> 5V I am connecting to input on pin 16? I am measuring the pin 16 from the
> scart pin so it is disconnected from the SCART to HDMI adapter (as you can
> imagine).
For the voltage to be about 3V it must be measured with the HDMI adapter connected. The circuitry inside the HMI adapter forms the other half of a voltage divider circuit with the 100 ohm resistor and causes the voltage to drop to 3V (or close to it). If you are not getting any video at all, make sure the wires connecting to the CoCo 3’s composite output are connected properly. For a simple test, you can connect only the composite output of the CoCo to the SCART input, leave the 5V supply disconnected, and you should see a composite video picture. Also, please note this circuit only works with a US NTSC CoCo, you don’t have a foreign PAL video CoCo do you? Richard Lorbieski builds and sells prebuilt cables as well.

https://www.facebook.com/rlorbieski <https://www.facebook.com/rlorbieski>