Hickok 539A settings

I wanted to test 6550's on this old beast and noticed these weren't listed on any of the scroll or supplementary charts. EL34'S were listed though. I had found the set ups and readings for an EL34,on a newer Hickok, and the set up is OK but meter readings are very different than for 539A. Anyone have a clue? Thanks
After poking around a bit and l came to a general consensus of opinion.First off,the 539A seems to set up a little differently than the B and C models. Tried a recommended set up for them and nothing worked.Found 2 great sites for those of us that have Hickok testers.Both Mr. Straub and Mr. Padgett have much info to share on these really neat pieces of equipment.They're also well built,a joy to operate,and I consider it industrial art.So anyway,what I came up with is: JR-5347-2 1.4v bias and a reading of 6000 on the A scale. This seems to only apply to the 539A.