Hickok 539C - Further Control Functions and Tests; Heater Cathode Leakage Detection; Noise Test Procedure; Leakage Resistance Meter Test

KIND OF SHORT
I 2 3
4
5
HEATER
-
CATHODE X
HEATER
- GRID
X
X
HEATER
-
SCREEN
X X
X
HEATER
-
PLATE
X X X X
HEATER
-
SUPPRESSOR X X
X X
X
CATHODE -
GRID
X
CATHODE -
SCREEN X
X
CATHODE -
PLATE
X
X
X
CATHODE -
SUPPRESSO~ X
'X
X
X
GRID
-
SCREEN
X
GRID
-
PLATE
X
X
GRID
-
SUPPRESSOR X X
X
SCREEN
-
PLATE X
SCREEN
-
SUPPRESSOR X
X
PLATE
-
SUPPRESSOR
X
6a~ Heater Cathode Leakage: A particularly troublesome defect in tubes, especially
those used in television, is a leakage between heater and cathode. This leakage
may be quite high, somet.imes running to several megohms. It may be too high to
cause the neon lamp to glow in the ordinary way. However, these leaks may be de-
tected on your new 539C.
You will note that a heater-cathode short will cause the neon lamp to glow on posi-
tion 1 (one). While the short switch is resting on position 1 (one), during short test
operation a condenser will be charging through the leak. If the switch is turned
from position 1 (one) to position 2 (two), a sharp flash of the neon lamp will be seen.
This will not repeat until the switch is again turned to position 1 (one) allowing the
condenser to recharge through the leakage. Many baffling cases of trouble can be
located in this way.
It has been established that heater cathode leakage as high as 30 megohms will cause
"noise" in repeater circuits in television service on coaxial lines.
6b. Noise Test: The short test circuit is also used in making noise tests on vacuum
tubes. Connections are made from the nOise test jacks to the antenna and ground
posts of any radio receiver. The tube under test is tapped with the finger as the
SHORTS switch is turned through positions 1-2-3-4-5.
Intermittent disturbances which are too brief to register on the neon lamp will be re-
produced by the loud speaker as static.
7. Leakage Test on Meter: An added feature in the Model 539C is its ability to measure
element leakage up to 50 megohms on the dial of the large Gm meter. The research
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