inner air pipette valve was conducting. at first diagnosed as leaking bellows on Y. but further investigation with helium revealed that Z was actually conducting. Most evidence at first pointed to leaking bellows on Y (blank was greater than a normal air shot) but a few tests conclusively proved that Y was leak tight and Z was conducting.
replaced valve driver for manual valve above air tank
inner air pipette valve was conducting. at first diagnosed as leaking bellows on Y. but further investigation with helium revealed that Z was actually conducting. Most evidence at first pointed to leaking bellows on Y (blank was greater than a normal air shot) but a few tests conclusively proved that Y was leak tight and Z was conducting.
replaced valve driver for manual valve above air tank