horizontal axis. Once set, you should not have to
The 1000 is used on boards and systems with
adjust these controls during normal operation.
ALL voltage sources in a power-off condition. A
0.25 ampere signal fuse (F1) connects in series with
Turn the power off by pushing the power
the channel A and B test terminals. Accidentally
switch in. When you turn the power on again, the
contacting test leads to active voltage sources
same intensity setting will be present.
(e.g., line voltage, powered-up boards or systems,
charged high voltage capacitors, etc.) may cause
The 1000 has three impedance ranges--low,
this fuse to open, making replacement necessary.
medium, and high. To select these ranges, press
When the signal fuse blows, the display shows
the appropriate button on the front panel. Always
open circuit signatures, even with the test leads
start with the medium range; then you can adjust
shorted together.
for other ranges. If the signature on the CRT is
close to an open (horizontal trace), try the next
higher range for a more descriptive signature. If
CAUTION
the signature is close to a short (vertical trace),
try the next lower range.
The device to be tested must have all power
turned off and have all high-voltage
There are two channels (channel A and
capacitors discharged before connecting
channel B) that you can select by moving the
the 1000 to the device.
toggle switch to the desired position. When using
a single channel, plug the red probe into the
The line fuse (F2) should only open when there
corresponding channel test terminal. Then plug
the black probe into the common test terminal.
is an internal failure inside the instrument.
When testing, connect the red probe to the
Therefore, you should always locate and correct
positive terminal of the device (i.e., anode, +V,
the problem before replacing F2.
etc.). Connect the black probe to the negative
The front panel of the 1000 makes function
terminal of the device (i.e., cathode, ground, etc.).
selection easy. The 1000 uses interlocking push-
By following this procedure, the signature will
button switches for range selection. A toggle
appear in the correct position on the CRT display.
switch is used for channel selection, and integral
LED indicators show the active functions.
The alternate mode of the 1000 provides
automatic switching back and forth between
The CRT displays the signatures of the parts
channel A and channel B. This allows easy
under test. The display has a graticule consisting
comparison between two devices or the same point
of a horizontal axis that represents voltage, and
on two circuit boards. You select the alternate
a vertical axis that represents current. The
mode by moving the toggle switch to the ALT
horizontal axis is divided into eight divisions,
position. The alternate mode is useful when
which lets you estimate the voltage at which
comparing a known good device with the same
signature changes occur. This is mainly useful in
device whose quality is unknown.
determining semiconductor junction voltages
under either forward or reverse bias.
The signal section applies the test signal across
Push in the power on/off switch. The 1000
two terminals of the device under test. The test
should come on line with the power LED
signal causes current to flow through the device
illuminated.
and a voltage drop across its terminals. The
current flow causes a vertical deflection of the
Before you can analyze signatures on the
signature on the CRT display. The voltage across
CRT, you must focus the 1000. To do this, turn
the device causes a horizontal deflection of the
the intensity control to a comfortable level. Now,
signature on the CRT display. The combined
adjust the focus control (back panel) for the
effect produces the current-voltage signature of
narrowest possible trace. Aligning the trace is
the device on the CRT display.
important in determining the voltages at which
changes in the signature occur. With a short circuit
An open circuit has zero current flowing
on channel A, adjust the horizontal control until
through the terminals and a maximum voltage
the vertical trace is even with the vertical axis.
across the terminals. In the LOW range, a
Open channel A, and adjust the vertical control
diagonal signature from the upper right to the
until the horizontal trace is even with the
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