The Hickok 750 is a Mutual Conductance tube tester. Mutual Conductance tube testers are the best for true vacuum tube performance. When matching tubes, this is the best type of tester to use.
The meter movement on this tester has been replaced. The original meter movement developed a mechanical problem. The needle came unglued from the movement coil. A quick fix got it going for the short term, but a new replacement meter was installed.
This tube tester is in pretty good shape. A lot of the old Hickok tube testers were work horses and were used daily. This resulted in a lot of wear on most of them. The case on this particular unit is not too badly beat up. There are a few nicks and scratches; overall the tester is in good condition.
There is no calibration procedure available for the 750, but several other models of Hickok tube testers are very similar and the calibration procedure can be used from these other testers. I calibrated this tube tester using what information was available. The shorts testing circuitry was pretty far off. Most every tube I tested before calibration showed a short. It now works properly following the calibration.
What I particularly like about this tester is that I can check for overall tube quality and also check Mutual Conductance.
I have found a lot of tubes that will check good on an emission tester will test bad on the 750.
Hickok tube testers command a premium price these days, but overall this 750 is a nice tube tester and well worth the investment.