I need help setting bias

I'm having a problem trying to set the bias on an Audio Research CA50 integrated. The optimal setting is 65ma, but the highest setting I can get using the bias adjustment is 50-52. The output tubes are 6550, and the input and drivers are 6922. I swapped the 6550's for newer ones but it made no difference. What would be the reasons for not getting a higher bias setting? Thanks in advance
I'd check the driver tubes for good measure.
Thanks Detlof, I didn't think the driver tubes could affect an output tubes bias. I can't check the driver tubes, but I can replace them with spares.
Audiojerry, I am not sure, not knowing your configuration, but I had a similar case years ago with an ARC D-79 and checking the driver tubes solved the problem if I recall right.
I learned that I was trying to measure using mA setting instead of mV setting. I should have been measuring in millivolts. Everything is great now. Thanks for your help.
So glad for you, should have thought of that eventuality, also happened to me before to my utter confusion. One lives and learns. Cheers,