Weston 981 Tube Tester

This is a Weston 981 tube tester that was not functional when I received it for calibration.  An electrolytic capacitor was shorted and blew a fuse when the line adjust was turned up so I had to replace it.  This tube tester uses selenium rectifiers instead of vacuum tube rectifiers.  I try not to replace selenium rectifiers with solid state diodes because this affects the calibration of the tube tester.  The tester was designed for the voltage drop across the selenium rectifier and is difficult to replicate with solid state diodes.  Luckily the selenium rectifier was not affected by the shorted capacitor.  I had to replace the line adjust pot because it was bad.  The line adjust pots in the old tube testers are wire wound pots with around 25 watt handling capability.  They are still available in NOS or as new units.

The Weston 981 tube tester is a mutual conductance tube tester and provides good quality testing of vacuum tubes.

Contact me if you have a tube tester you want calibrated.