Simpson 1000 - Page 24

OPERATING INSTRUCTIONS
commercial standards. However, if there is a dead short,
with zero ohms, or a leakage resistance with less than
250K ohms of resistance, the indication will be in the red
marked area of the dial, indicating a condition which is not
normally acceptable.
There are some cases when a leakage resistance with a
relatively low value may be used in a circuit which has low
impedance; on the other hand, a very high value of leakage
resistance may cause trouble in high impedance applica-
tions. It is possible for you to identify which elements are
involved in a leakage circuit if you need to evaluate the
tube usability with these special considerations. See Sec-
tion VI, Special Applications, for this information. Do not
test any unsatisfactory tube beyond this point.
CONTROL-GRID, SCREEN-GRID, PLATE VOLTAGE
When the short tests are finished, and the tube is consid-
ered satisfactory for further checking, press the push but-
ton, or buttons, listed under VALUE on the chart, and then
press the LINE TEST button. Up to this point, the filament
of the tube has had voltage applied across it, but all the
other elements have been connected to ground. When you
press the LINE TEST button, you apply control grid,
screen grid, and plate voltage to the tube and it begins to
conduct current.
The amount of current does not register on the meter, but it
will load the transformer the same as it will during the
value test which follows, so you can reset the LINE AD-
JUSTMENT control when it is necessary to correct for the
loading effect.
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