Hickok 6000A - Mutual Conductance Test; Rectifiers, Diodes, and Thyratrons; Gas (Grid Current) Test; Life Test

condition of tube, If the vacuum tube is good, the needle onthe test meter
will remainin the area marked LINE TEST, or move into the GOOD area.
If the tube is faulty, the needle on the test meter will move into the RE-
PLACE area. Disregard the MICROMHOS scale.
d. MUTUAL CONDUCTANCE TEST
The SHUNT setting listed on the roll chart is used to read the
condition of the tube being tested on the REPLACE-GOOD scale. The
number listed on the roll chart under the heading of FUNCT. AND MUT.
COND, indicates the Mutual Conductance of the tube. The SHUNT control
has three red dots stamped into the metal and marked 3000, 6000, and
15,000. These numbers correspond with the meter scale to be used. The
red dots indicate the exact setting of the shunt control for the separate
scales. The scale to use is determined by the roll chart data. For ex-
ample: If the mutual conduction of a particular tube is listed as 5400.
(5400 micromhos). Set the SHUNT control to the red dotvat 87 and read
the value of mutual conductance on the 0-6000 micromho scale.
e. RECTIFIERS, DIODES AND THYRATRONS
Rectifier tubes, including diode tubes and diode sections of mul-
tiple element tubes, having no mutual conductance are tested for emission
only. When the red button marked TEST is depressed, good rectifier and
diode tubes will cause the needle on the meter to move above the point
marked DIODES OK. In checkingthyratrons, such as the 884 and the 885,
the BIAS control should be set at 100 which is the highest negative value.
Depress the TEST button, and hold down while the BIAS control is gradu-
ally turned counterclockwise until the tube strikes, that is, begins to
conduct, which is indicated by a sudden deflection ofthe needle on the test
meter.- The NOTATIONS-column of the roll chart indicates the approxi-
mate point at which the tube STRIKES. After the tube STRIKES, or be-
gins to conduct, it should produce a steady meter reading in the GOOD
area of the scale.
f. GAS (GRID CURRENT) TEST
= Some tubes develop gas after being heated for a period of time.
When a tube has a gas condition, the grid current will increase and cause
the tube to over-conduct. If a tube is suspected of a gaseous condition,
set all the controls according to the data on the roll chart. Depress the
red button marked TEST and the button marked GAS. Test meter will now
indicate the grid current up to 100 microamps. Grid currentin excess of
two microamps is undesirable. If the tube being tested causes the needle
onthe test meter to move more than two small divisions, it should be dis-
carded.
с, LIFE TEST
The purpose of a life test is to determine how long the tube may
be expected to perform satisfactorily. Ascertain that all of the controls
are set as indicated on the roll chart. Depress the red button marked