(Translated 2005-11-23)
Source lost in translation.
One of the most frequent questions is: how can i add a BAS video output to my ZX81?
The circuit diagram:
A universal NPN NF transistor is sufficient. Be careful in regard to statical electricity, because the ULA is very damageable by statical dischargements. The input signal can be accessed at pin 16 of the ULA or the modulator input wire.
The photograph shows the inputs of the modulator box. In the middle (left wire) is the video signal and the right wire serves +5V, the modulator's case is connected to GND.
Kio's comment (2005-11-05)
This circuit is simpler than the other but a little bit brute-force. I think that the signal level is too high. (to be verified.)
The other circuit video output II.html has the additional advantage, that the video signal is mixed to the TV UHF signal, so that you can connect the TV output to video-in or antenna of a TV set, whatever is available.