EG&G ORTEC 113 Manual de operação e serviço - Página 7
Procurar online ou descarregar pdf Manual de operação e serviço para Amplificador EG&G ORTEC 113. EG&G ORTEC 113 9 páginas. Scintillation preamplifier
Imprimir página5. CIRCUIT DESCRIPTION
Switch 81 permits adjustment of the input capacity of the
113 for reasons discussed in the preceding section. Diodes
D1 and D2 protect Q1 by preventing the excursions of the
base of Q1 from exceeding ±12 V when a positive or
negative high voltage is abruptly applied to the input
connector. Q1 and Q3 make up an emitter white follower
with a gain of (R9 + R4)/R4.
Q2 has been added to increase the current gain for negative
pulses. C8 bootstraps R2 to produce a high input resistance.
Resistors R20 through R23 set a fall time constant of 50
jusec for the output pulse, assuming a driving source
impedance of 1 x 10® J2. The output impedance of the
amplifier section is approximately 2J2; therefore the output
impedance at connector CN3 is equal to R16 plus R24 for
all practical purposes. R24 should be adjusted so that R24
plus R16 is equal to the characteristic impedance of the
cable connected to the output CN3, unless the cable is
terminated at the receiving end.
6. MAINTENANCE INSTRUCTIONS
6.1. TESTING PERFORMANCE
Insert a voltage pulse in the Input connector and monitor
the output with an oscilloscope. The output pulse should be
equal to the input pulse when the output is not loaded and
equal to one-half the input pulse when it is loaded with
93J2 and R16 plus R24 is equal to 93^2. Perform this test
with both positive and negative input pulses.
Insert a voltage pulse into the Test Pulse input connector
and monitor the output pulse with an oscilloscope. For each
volt input an output voltage of approximately 135 mV
should be obtained when an input capacity of 100 pF is
selected by SI. The output pulse should decrease in am
plitude as the input capacity is increased.
6.2. SUGGESTIONS FOR TROUBLESHOOTING
Perform the tests outlined in Section 6.1. If an output pulse
of the proper magnitude is not obtained, check all dc
voltagesand compare them with the values tabulated below.
6.3. DC VOLTAGES
The voltages listed below will help to locate defective
components. All voltages are measured with respect to
ground.
Typical dc Voltages
LOCATION
DC VOLTAGES
+24 V Supply
-24 V Supply
Qle
Qlb
QIC
Q2e
Q2c
Q3e
Q3b
+24
-24
-1.0
-0.5
+ 13.3
+ 13.8
-1.65
-13.2
-12.6
6.4. 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
checkout that are used for a new instrument. Always
contact Customer Services at ORTEC, (615) 482-4411,
before sending in an instrument for repair to obtain ship
ping instructions and so that the required Return Authori
zation Number can be assigned to the unit. Write this num
ber on the address label and on the package to ensure
prompt attention when it reaches the ORTEC factory.