Post by SimonMan, Just look at them. It's kind of obvious which is better. My understanding is that the only Hickok that can go toe-to-toe with an AVO from the same era is the military grade TV-7 and it's derivatives.
Yes, 20 years later, but NO, the TV-7 is nowhere near as adept as its reputation. That it is a military tester accounts for its ruggedness, but not for much of anything else. It was designed to do go/no-go tests of tubes in military equipment under field conditions, quickly, and with some ability to distinguish quality - one tube relative to another of the same type. But it is not designed for matching, one cannot measure plate or filament current, anode current, nor any other parameters required to 'match' tubes without considerable additional adaptors and other equipment. One cannot set bias internally, nor supply bias current from the outside.
For any of that, the 539-series is required, with specific reference to the B & the C, which have points built in where all of that may be measured or set.
The AVO may be a bit fussy and complicated, but it is (at least) three times the tester as the 752 - which, put simply, is a non-ruggedized TV-7 in terms of complexity and capacity. That TV-7 testers command insane prices is more a reflection of the ignorance of their buyers than the quality and utility of the tester as it relates to actual function.
NOTE: I keep a Hickok 539B and a Simpson 555 tube tester. For 90% of my work, the 555 does just fine. Only when I need to match will I trot out the 539B.
Peter Wieck
Melrose Park, PA