Jackson 648 tube testers

Anyone have any experience with the Jackson 648 tube testers? I am looking to test 6DJ8/6922/12AX7/6CA4/6SN7/7024/ tubes, etc. I read the recommendations on Hickok and B&K testers but there was no info on the Jackson tester. I want to get testing results and not spend to much on a tester. I see the Jackson testers for $100 with manuals and calibration instructions.

I have 2 ...actually 3 testers.They are good enough to test those tubes mentioned above. As long as your 648 is calibrated.I checked and tested all of my tubes with my Jackson 648A.Hope this help.pescolar
Thanks for responding.
I just came across an ebay listing for a calibration tube for the 648 tester. Not sure if you need one but If you are interested the listing number is 160828299076
Good luck.