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How To Test CRT Anode Voltage With Your
VA62A Digital Meter And The HP200
One of the most critical voltages in a television
set is the second anode high voltage. In order for
the CRT to emit the proper amount of light, the
high voltage must be at the correct level. If the
high voltage is low, the CRT will have a dim
picture or no picture at all. If the high voltage is
too high, the picture will become distorted, the
set may go into shutdown, or permanent dam-
age to the high voltage circuits may occur.
Using the HP200 50kV High Voltage Probe with
the V A62A digital meter allows you to measure
these high voltages up to 50,000 volts. When
measuring high voltages, however, proper steps
and precautions must be taken to insure accu-
rate and safe
readings.
v
Figure 1: Simply multiply the VA62A 's digital
meter reading by 100 to obtain the value of
the voltage being measured. For the example
shown, the reading of 244 volts represents a
circuit voltage of 24,400 volts.
HP200 Extends The VA62A
Impedance Range
The VA62A's digital DC meter has an input im-
pedance of 15
megohms.
This high
input
imped-
ance lets you make measurements up to 2000
volts, with a direct
probe,
in virtually every circuit
without loading them down.
The HP200 extends the VA62A's impedance to
1500 megohm, 100 times the original imped-
ance. This high impedance divides the voltage
down by a factor of 100 before the voltage
reaches the VA62A's circuits.
Since the voltage is being divided by 100 by the
HP200, the voltage reading on the VA62A's
digital display will be smaller by a factor of 100.
To obtain the value of the voltage being meas-
ured, the reading must be multiplied by
100,
or
simply move the decimal two places to the right.
For example,
if
you get a reading of 244 volts on
the VA62A's digital meter using the HP200, the
actual voltage would be 24,400.
Setting Up The VA62A And HP200
Using the HP200 and VA62A to make a high-
voltage measurement is similar to making
nor-
mal DC measurements except for the
100
times
multiplication factor. You start by setting
the
VA62A's DIGITAL METER switch to the EXT
DCV 2KV DIRECT position. The supplied meter
probe and ground lead are inserted
in
the EXT
PPV & DCV and ground jacks,
respectively.
Then you slip the probe into the special connec-
tor on the rear of the HP200 as shown in Figure
2 and you're ready to test.
Safety Precautions
Measuring voltages above 2000 volts with the
HP200 and the VA62A presents possible shock
hazards. Be sure to read the following
warnings
and instructions before attempting to make any
kind of high
voltage
measurement:
Discharging the CRT anode
Modern CRTs may retain a high
voltage
charge
for a substantial period after power is
removed.
Before working in the high voltage section, or
attempting high voltage measurements, the CRT
must be discharged.
Figure 2: The HP200 fits over the end of the regular test probe and increases the measuring
capabilities to 50,000 volts.
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