Before adjusting one of these be certain that;
1. It needs adjustment !
2. You have a really good monitor, you can rely on.
3. A vector scope is really required doing it by eye is a waste of time and a scope
is the minimum you can use.
VRa-g are repeated for each input channel and only affect the digitised quad output results.
VRh-u only effect the overall quad output.
Selecting an input channel for direct display bypasses all circuitry other than the output buffer.