539B

About the 539B

The Hickok 539B is a late-model transconductance tube tester designed for precise and repeatable testing of vacuum tubes. It features separate bias and AC line voltage meters, which have been upgraded in some units to new, accurate analog meters with added bias fuse and protection diodes. The 539B can test a broad range of tubes, including common audio tubes like 6CA7, 6L6, 6SN7, KT88, and voltage regulator tubes such as 0A2. It is similar to the 539C model, with the main difference being that the 539C includes two additional sockets for compactron tubes. The tester is all solid-state and often comes clean and calibrated, with manuals and tube data available digitally. It is valued for its robust construction, including a well-balanced heater circuit and multiple socket options, and is considered a top-tier tube tester for both hobbyists and professionals. The unit typically weighs about 20 pounds and includes features like an auxiliary on/off switch controlled by the lid. The 539B was also produced in a Western Electric version (KS 15750 or RD1575) with specific tube listings such as 300B tubes. Calibration and maintenance notes include replacing certain resistors for stability and careful zeroing of filamentary noise for accurate readings.