[Findm-Keepm]

Most emission-only testers have limited means of calibration. The Heathkit and Eico probably have some alignment instructions in the assembly manual. The B&K has an adjustment procedure for alignment - not sure of the details, but one of my B&K's required a "select at test" resistor.

The TV-7, and most Hickok testers are mutual conductance testers, and are calibrated in micro or milli-mhos. The calibration often is by a precision resistance, a voltage, or a "standard" tube. Each calibration procedure is different - I've only calibrated TV-7D/U's (while I was a Navy calibration technician) and one B&K 747 tester, both conductance testers. The 747 calibration put many known-good tubes in the questionable or bad category, so even calibration doesn't assure an accurate test.

There are some "purists" out there that insist that their tubes only be checked on a Hickok tester. The real world is the best tester of all. Many here have seen it - a tube that checks great on the tester, but fails in the circuit (RCA 3.58 MHz oscillator or burst amplifier, anyone??) All too often, you'll see eBay sellers touting tubes that read "110" or some other meaningless number. Worse yet is the "matching" of tubes on a tester. The real world circuits have different bias and plate voltages, different impedances, and different frequency characteristics, so the tube tester matching is often irrelevant.

Just my 2c. Over on AK you'll probably get a whole dollars worth of answers.

Cheers,