What are you doing exactly?
Did you see
http://cpcwiki.eu/index.php/TV_SCART_cable ?
Are you using the same connection, but still get problems?
Of course, the batteries in above schematics aren't that optimal. Using a resistor to 5V to produce 1V-3V would be better than batteries. But it with different TVs you may need different resistors. Maybe best would be using two 1K Ohm resistors:
GND ------1K-------x------1K------5V
In the middle (x) you should get perfect 2.5V. And even if the TV drags it down a little, you should still be in the 1V-3V range. Btw. you don't have a multimeter to verify what voltage you have, or do you?