EG&G ORTEC 426 Manual de funcionamiento y servicio - Página 12
Navegue en línea o descargue pdf Manual de funcionamiento y servicio para Unidad de control EG&G ORTEC 426. EG&G ORTEC 426 16 páginas. Linear gate
Imprimir página8. Remove the All Output from the linear Input on the
426. Rotate the Gate Width control over its entire range and
measure the resultant gating period. The' minimum should be
0.3 jjsec or less and the maximum should be 4 jusec or
greater.
6.2. ADJUSTMENT OF LINEAR GATING DURATION
The linear gating period is continuously variable from
approximately 0.3 jusec to 4 ixsec. The pulse width is
controlled by capacitor C8 and resistors R34 and R35. To
change the gating duration, simply adjust the control R35,
which is recess-mounted on the front panel.
In the event that gating durations different from 0.3 to
4 jusec are desirable, the capacitor C8 may be replaced with a
capacitor of different value to change the range of gating
duration. R35 will provide continuously adjustable pulse
width within the new range.
6.3. ADJUSTMENT OF LINEAR GATE PEDESTAL
The Linear Gate has a trim potentiometer, R11, to allow the
pedestal on the Linear Gate Output to be reduced to a
negligible value, typically 1 mV. R11 is located near the top
of the etched circuit board. To adjust the pedestal it is
necessary to open the Linear Gate, with no input signal
feeding into the Linear Gate input CN1 while observing
with an oscilloscope the output of the Linear Gate.
Observing the Linear Gate output, adjust the pedestal trim
potentiometer until the pedestal is reduced to a negligible
amount.
6.4. TABULATED TEST POINT VOLTAGES
The following voltages are intended to indicate the typical
dc voltages measured on the etched circuit board. In some
cases the circuit wil l perform satisfactorily even though, due
to component variations, some voltages may measure out
side the given limits. Therefore the voltages given should
not be taken as absolute values, but rather as an aid in
troubleshooting.
6.5. SUGGESTIONS FOR TROUBLESHOOTING
In situations where the 426 is suspected of malfunction, it
Table 6.1.
Pin No.
Test Point
Voltage (V)
1
Q7e
-1-
0.2
2
Q4b
- 0.61
3
Q5b
-
1.7
4
Q9c
-r
10.9
5
Q12c
-f-
11 .4
6
Q13B
+
0.6
Note: All voltages were measured from ground with vtvm having
input impedance of 10 mf2 or greater. Voltages are dc values with
no input pulses.
is essential to verify such malfunction in terms of simple
pulse generator impulses at the input and output. In
consideration of this, the 426 must be disconnected from
its position in any system, and routine diagnostic analysis
performed with a test pulse generator and oscilloscope. It
is imperative that testing not be performed with a source
and detector until the amplifier-Linear Gate system and the
logic system perform satisfactorily with the test pulse
generator.
The testing instructions in Section 6.1 of this manual and
the circuit descriptions in Section 5 should provide assist
ance in locating the region of trouble and repairing the
malfunction. The guide plate and shield cover can be
completely removed from the module to enable oscillo
scope and voltmeter observations with a minimal chance of
accidentally short circuiting portions of the etched board.
6.6. FACTORY REPAIR
This instrument can be returned to the ORTEC factory for
service and repair at a nominal cost. Our standard proce
dure for repair ensures the same quality control and check
out that are used for a new instrument. Always contact
Customer Services at ORTEC, (615) 482-4411, before send
ing in an instrument for repair to obtain shipping instruc
tions and so that the required Return Authorization Num
ber can be assigned to the unit. Write this number on the
address label and on the package to ensure prompt atten
tion when it reaches the ORTEC factory.