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CUPS TO DEFLECT ON PLATE P NS
NOTE:
TO AVO D GROUND NG
LEADS USE NSULATED
SLEEV NG WHERE
NECESSARY.
Fig. 2-13. Typical circuit for ac coupling to the crt deflection plates.
coupling is shown in Figure 2-13. Here, the leads from the
oscilloscope amplifier are removed and a resistor is con
nected between each lead and its respective crt pin.
good value for this resistor in most cases is 1 megohm. The
vertical deflection plate pins are located on the sides of
the crt neck and the horizontal deflection plate pins are
located on the top of the neck.
convenient
method
for
the crt pins is to use clips removed from standard miniature
®1
4=0. 1
nt
TO S GNAL
SOURCE
connecting
the
resistors
to
Operating
tube sockets.
Before connecting the resistors to the leads
from the amplifier, slip a piece of insulated sleeving (spa
ghetti) over the wire.
Then, after making the connections,
draw the sleeving back over the insulated resistor pigtail.
This will prevent the leads from accidentally shorting to the
chassis. The crt pins are easily bent and you must exercise
care when making these connections to avoid breaking the
glass seal.
C UTION
Do not allow the leads from the oscilloscope am
plifiers to touch the chassis when the power is on.
short circuit of this type can damage the ampli
fier circuits.
If it is desired t o couple the signal directly to the crt plates
(d c coupling), it will be necessary to supply positioning volt
ages from the signal source. These voltages must also satisfy
the
requirement
of
an
average
mentioned previously. To d c couple the signal to the deflec
tion plates, remove the leads from the crt pins and fold them
back, out of the way.
Taping the ends of the wires will
prevent accidental shorting to the chassis. Connect the exter
nal signal source to the pins of the crt.
The vertical deflection factor of the crt is approximately
13 volts per centimeter.
The horizontal deflection factor is
approximately 17 volts per centimeter.
nstructions — Type 502A
level
of +225
volts,
2-11
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