Philips PM 6671 - 4. Performance Check; Oscillator and Frequency Response Checks; Input C and Trigger Level Checks

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4. Performance Check
Required Test Equipment
• Voltmeter, e.g. Philips PM 2517
• Frequency counter, e.g. Philips PM 6650
• Oscilloscope, e.g. Philips PM 321 5
• Sampling oscilloscope, e.g. Philips PM 3400
• Pulse generator, e.g. Philips PM 5771
• Function generator, e.g. Philips PM 5131
• HF signal generator, e.g. Wavetek 2002A
• Probe, lOMohm, 120MHz
• FET probe, e.g. PM 9354
• T-piece, BNC-type
• Temination, 50ohm, BNC-type
Initial set-up
All pushbuttons should be in a realeased position.
Set MEASURING TIME to 10ms (fully anticlockwise)
and HOLD OFF (PM 6671) to 0 (off). Pull both
TRIGGER LEVEL/SENSITIVITY potentiometers (i.e. AC
mode) and turn them fully clockwise. Select FREDA.
The slide switches on the rear panel should be set
to INT STD and EXT RESET (not applicable to
PM6670). Set the line voltage slide switch on the rear
panel to the local line voltage. Connect the counter
to the line and press POWER ON.
Check of the oscillator
The /01 version of PM 6670...72 can be checked
by connecting the 10 MHz OUT from a counter, e.g. a
PM 6650 or a PM 6673 equipped with at least a
calibrated TCXO, to connector D on the rear panel via
a 10 Mohm probe. The frequency should be 10 MHz
± 10Hz.For/02.../05 versions, please referto Section,
Optional Oscillators in the service manual.
Check of the sensitivity and
frequency response
• Connect a signal generator and an oscilloscope via
a T-piece to input A.
J O C)
I g i O g ; o ig j
• Check the sensitivity at the following frequencies:
50Hz...75MHz : 25mVpp
75...120MHz : 50mVpp
Check of Input C (PM 6672 only)
• Connect a RF signal generator and a sampling
oscilloscope via a T-piece to input C. Use a FET
probe on the oscilloscope.
• Set the amplitude to 1 5mVRMS ( — 24 dB) and
vary the frequency between 70 MHz and 800 MHz.
The counter should measure correctly.
• Set the generator to 1GHz with 25mVRivis
(-1 9dB) amplitude. Check that the counter displays
a correct value.
• Push CHECK.
• Adjust the measuring time and check the display
read-out as follows.
Measuring time
1 0ms
100ms
Is
1.5s
' Release CHECK.
Display read-out
0.25600GHz
256.000MHz
256.0000MHz
256.00000MHz
Check of TRIGGER LEVEL
(PM 6671 and PM 6672)
• Push both TRIGGER LEVEL potentiometers.
• Connect a DMM to the trigger level output
connector for input A on the front panel.
• Vary the trigger level between both end positions.
• Check that the voltage can be adjusted between
-2.5 and -F 2.5V with a tolerance of 0.1 5V.
• Repeat the procedure for input B.
• Pull both TRIGGER LEVEL potentiometers and set
them fully clockwise.
• Use short 50ohm coaxial cables. If the signal
generator has a 50ohm output impedance, a
50ohm termination has to be used at the oscillo
scope. The termination should not be used with
a sampling oscilloscope (above approx 25MHz).
Check of COUNT A MANUAL
•Push CHECK.
• Select COUNT A MANUAL.
• Push DISPL HOLD and then RESET. Check that
the display read-out is 0 and the GATE LED is off.
• Release DISPL HOLD. The counter should start
counting and the GATE LED start blinking.