LM1881 Sync Separator
A lot of consoles do not offer composite sync, only composite video. C-video carries the C-sync information, along with a lot of extra crap many monitors don't need, and the result is an unstable display or a completely blank display. The LM1881 is a cheap ($3) chip that takes a C-vid signal and strips out the unecessary video data, resulting in a clean composite sync signal suitable for most monitors.
There's not much to it. Simply connect the chip as shown.
- You can safely ignore pins 3, 5 and 7.
- All the parts are small enough to fit in a DB9 connector.
- The LM1881 circuit is useful to generate a composite sync signal from a composite video signal. Connecting a c-sync signal to the input of an LM1881 may cause problems and should be avoided.
- It should include a 75 ohm (or thereabouts, the value isn't critical) resistor between the input and ground, before the coupling capacitor. This sets the optimum video level and combined with the lower line impedance and reduced noise, give the LM1881 a much better chance of seperating the sync from a video signal which is changing from bright to dark rapidly.