detect current flow (a meter or neon lamp) in series with the voltage
source will then indicate whether a short exists.
Switches on the
tube tester allow connection of the voltage source across any two
suspected electrodes.
3-8.
FILAMENT CONTINUITY TEST
Frequently a tube's filament burns out, leaving an open circuit
between the filament electrodes.
A filament continuity test is
performed in the same manner as a short test.
A voltage source is
connected across the filament electrode, and current flow indicates
the filament is "good," that is, not open-circuited.
3-9.
USING A TUBE TESTER
Most tube testers will perform a variation of some or all of the
tests discussed.
The transconductance (gm ) and emission tests are
the basic tests performed on most tube testers.
It should be
remembered, however, that a tube tester only provides an estimate of
the condition of a tube. Many tubes will pass all tube tester tests
and yet not operate properly in a certain circuit.
The ultimate
check on a tube's operation is to ascertain whether is does its job
in the circuit in which it is said to be used.
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