321,
Great suggestion ! Yes, when I bypass the gyro, it tests out just fine. However....

The problem is still not cured because when I fire up the heli in HH mode, the gyro is not working properly. It rotates slowly (nose right) and the red light double-blinks which indicates that "... the rudder signal from the transmitter in the AVCS mode is different from the neutral signal memorized in the gyro ..." (according to the gyro manual). It initializes fine but starts to blink once throttle is applied. When I switch to non-HH, it works OK (albeit I probably need to adjust the mix a little). I have always kept the gain at 100% in the past and it doesn't make a difference what I set the gain to now.
Any ideas

Another issue I have is with the main rotor head. It wobbles. I have replaced the main shaft and bearings and the head itself. W/o the head the shaft rotates dead center perfect but when I put the head on (no grips, no links, just the head), it wobbles. I have tried putting it on several times. When I start the heli, it shakes a little until I get close to lift-off speed and then it's solid.
Any ideas on how the install the head so it doesn't wobble ?

TIA