Leader LTC-905 User manual

LTC-905
CURVE TRACER
SERVICE MANUAL
Leader Instruments Corporation
6484 Commerce Drive, Cypress, California 90630 Tel; [phone] Fax: [phone]
Regional Offices: Atlanta, Boston, Chicago, Cleveland, Dallas, Los Angeles, New York

CONTENTS
Page
1.Test Equipment Required 2
2. Calibration Procedure 2
3. Troubleshooting Procedure 4
4- Printed Circuit Board &
Location of Adjustment 5
5. Block Diagram 6
6. Schematic Diagram 7
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NOTE
These servicing Instructions are for use by
qualified personnel only. To avoid electrical
shock, do not perform any servicing other than
that contained in the service manual unless
you are qualified to do so.
_1 _
LTG-9,05

1.Test Equipment Required
The following test equipment is required for calibration
and servicing of the Model LTC-905. The suggested
specifications are the minimum necessary for proper calib-
ration of this instrument.
Test Equipment Minimum Spec,
oMultimeter Accuracy <±1^
oOscilloscope lOmV sensitivity
1MHz band width
2. Calibration Procedure
»Calibration should be performed after a30 minute warm-up
period. It should also be confirmed that the unit is
connected to the rated power line voltage.
*All adjustment should be completed in the given order,
because some adjustments interact with others.
*During the adjustment procedure, remove the case only
when necessary and replace immediately after making an
adjustment. This will maintain all circuit at constant
operating temperature.
1) Initial Control Settings
The initial control settings to be used for each check and
adjustment are listed below. Any variations from these
settings sre stated in the applicable procedure.
oPOLARITY
oCURRENT LIMIT
BASE ,GATE
°CURRENT"^ VOLTAGE
COLLECTOR/DRAIN
°SWEEP VOLTAGE
oTRANS. -FET
oSELECTOR
NPN
SIGNAL
0.1mA
10V
TRANS.
A
-2-
LTC-901

2) Power Supply
a) Connect DC voltmeter between the test point and chassis.
b) Check the voltage according to Table-1
Test point Voltage Tolerance
D106 +5V +4.5V to +5.5V
D105 +9V +8.2V to +10. 5V
D107 -9V -8.2V to -10.5V
Table-1
3) Staircase Generator
a) 0Level Adjustment
oConnect the DC oscilloscope to BASE/ GATE jack.
oAdjust STEP 0ADJ (VR101) for minimum base line shift when
POLARITY is switched between NPN and PNP as shown in Figure-1
line=0V
Figure -1
b) Amplitude Adjustment
oConnect the oscilloscope to BASE/GATE jack.
oAdjust NPN STEP ADJ (VR102) for amplitude of 3.5Vp-p with
seven steps as shown in Figure-2.
Figure-2
-3-
LTC-905

oSet the POLARITY switch to PNP.
oAdjust PNP STEP ADJ (VR103) for amplitude of 3-5Vp-p with
seven steps as shown in Figure-3
Figure-3
oRepeat a) and b) if necessary.
3. Troubleshooting Procedure
1)
Check all control settings, because an incorrect setting can
make agood unit appear defective.
2)
Some trouble can be solved with proper adjustment.
3)
Check the DC voltage and waveform as shown in the schematic
diagram to locate the defective circuit.
Start with the power supply.
4)
Check all circuit for visual defects such as broken components,
loose connections and poor soldering which could be acause
of trouble.
5) Troubleshooting Chart
-4“
LTC-905

4. Printed Circuit Board &
Location of Adjustment
-5-
LTG-905

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