I just installed a complete different head, from the swash up, on my CP that wouldn't take off. The blades would not go into positive pitch.
The new head.. removed from another crashed plane.. the thing wants to go up!
Links from the servo to the swash were the same.
The only visible difference is the lifting head shows more thread in the pitch links than the non-lifting head... both were set up the same pitch wise.
Beats me what's going on.
The small thread gap indicates too much negative pitch.. but it wasn't detectable with my pitch checking setup.