Bias Probe (Current Measuring)
Measures true bias current. For use with octal tubes EL34, E34L, 6CA7, KT66, KT77, 6L6, 6V6, 5881, 6550, KT88, KT90.
The Granger Amp bias probe measures in milliamps by insertion into the cathode connection that conducts the current to the plates of the tube. When using our probe one sets the multimeter to the DC mA (not DC Volts!) setting and selects a range of 200 milliamps if the meter is not auto sensing. Then insert the red plug into the jack labeled mA and the black plug into the common jack. The bias probe is placed into one of the amp's power tube sockets and the tube into the bias probe.
This is the most accurate way of measuring bias current, and only takes a few minutes to properly bias an amp that has a fixed, adjustable bias supply.
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