The Hickok 752A tube tester is widely recognized as one of the very best Hickok testers made. This unit is in great condition electrically and cosmetically. The case doesn't look great but the tester itself is very clean. All of the functions I checked work as they should. I cleaned and retensioned all of the tube sockets. This tester is ready to be put into service.
I checked all of the basic voltages and they are as they should be, including:
- plate voltage - screen voltage - bias voltage - heater voltage - signal voltage
Most of the calibration process involves getting these voltages right. So, this unit appears to be within calibration. I also checked the leakage test by inserting a 200k resistor across a couple of pins on a socket. The shorts test is measured in leakage and the meter read 200k on the appropriate test. So that is in calibration as well.
I also tested a variety of tubes (6L6GC, 12AX7, EL84/6BQ5, 6SN7) of known quality as verified on our Amplitrex AT1000. This 752A identified each tube's quality correctly. That's impressive to me for a vintage tester.
The 752A has a few very nice features not common on other testers. It has the ability to easily check dual triodes without having to reset the entire tester. It's just a second button to push to test the second section. It measures actual leakage on the meter rather than a simple pass/fail indicator light. It has a fuse built in to protect the bias circuit. There are many more reasons this is a highly regarded tester. Do some research online. There's a lot of good info out there.
I do not have the test lead for top caps on some tubes. This tester has test points for this. It should be noted that these test points are NOT standard banana sized. They are tip jack sized. I found that a typical probe from a multimeter fits snuggly in the test jacks, so a lead could easily be built to use those jacks if you needed to test tubes with a top cap.
Some features of the Hickok 752A include:
- The ability to test two sections of a tube without having to reset the switches—very nice for testing dual triodes and full wave rectifiers. - Sockets for nearly all of the desirable tube types from old 4 pin tubes like 45, 2A3, and 300B triodes all the way up to more modern compactron and pencil tubes. Of course, it also tests the most popular audio tubes like 6SN7, 12AX7, 12AU7, etc. - Leakage is measured on the meter so it’s not just a pass/fail reading. An informed user can make a better decision about how serious the leakage is and whether it is acceptable for that tube type and the intended application. - Terminals are offered so that a cathode bias resistor can be inserted into the circuit. This is very helpful for circuit design or for testing tubes that only really behave correctly with a cathode resistor in circuit. - The 752A provides AC signal voltages that are more appropriate than most of the older simpler Hickok designs. These voltages are 0.25vac, 0.5vac, 1.25vac and 2.5vac depending on the type of tube to be tested. This available range is SO much better than the older testers that had only one AC signal voltage available—typically either 5v or 2.5v, both of which are way too high to correctly test many tube types.