Racal Instruments 9915 User manual

9915
UHF Frequency Meter
Service Manual
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G0RSQ
29th June 2015
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Frequency Meter 9915
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CONTENTS
Page
SECTION 1TECHNICAL SPECiFiCATION
AND
SUPPLEMENTARY DATA
SECTION 2DESCRIPTION OPERATION
AND MAINTENANCE
CHAPTER 1GENERAL DESCRIPTION 1-1
CHAPTER 2 OPERA TING INSTRUCTIONS
OperaH
ng Instructions
2-1
Carrying Handle
2-3
Description of Controls 2-4
Indicators 2-5
Rear Panel Items 2-6
CHAPTER 3PRINCIPLES OF OPERATION
The CDI Chip
3-1
Basi cCounter Diagram
3-1
General Circuit Functions 3-2
Dynamic Display System
3-2
Mul tiplex Readout 3-3
Decimal Point 3-4
Control Codes 3-4
Resistor Arrays 3-4
CHAPTER 4TECHN ICAL DESCRIPTION
Introducti on
4-1
'A' Channel Input
4-1
Signal Path
4-1
'A IChannel Overload Protection 4-2
P. I. N. Diode Attenuator
4-2
Counter Enable Circuit
4-3
Automatic Gain Control 4-3
'B' Channel Input 4-3
Signal Input 4-3
'B 'Channel Amplifier
4-4
Input Selection 4-4
Channel Switching 4-4
24V Generator
4...:4
Input Signal Steering 4-4
Ancillary Steering Functions 4-6
One-Second Gate
4-6
Segment Check 4-6
9915 Vol. 2Contents (1)
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CHAPTER 5
9915 Vol. 2
Hold/Reset
Burst Mode
Summary
Burst Circuit
Function of Q21 and Q22
Data Output and Display System
Data Output Format
Multiplex Readout and Display
Decimal Point Selection
Overflow Indi cator LP1
Gate/Charging Indicator LP3
Power Supply
AC Supply
+5V Switching
Standby Indi cator
+5 and -5V Stabilization
Battery Economy Operation
Battery Charging
Charge Indicator
Battery Powered Operation
Battery Low Indi cator
Over-Discharge Protection
Frequency Standard
Standard
Osci "ator 19-0834
Frequency Doubler
1 MHz Reference Output
External Standard Input
LF Multiplier Assembly (Option)
MAINTENANCE
List of Test Equipment
Removal of Covers
Transformer Voltage Selection
Fuses
Power Lead
Power Supply Check
Performance Tests and Cal ibration
Segment, Decimal Point and Self Check
Sensitivity Check: Input 'B
I
Sensitivity Check: Input 'A'
AGC Output Check
Overload Indicator Check
Standby (Battery Economy) Check
Battery Charging Checks
Frequency Standard Ca I ibrati on
Dismantling
Removal
of Display PCB
Removal of Main PCB
4-6
4-6
4-6
4-7
4-8
4-8
4-8
4-8
4-8
4-9
4-9
4-10
4-10
4-10
4-10
4-11
4-11
4-12
4-13
4-13
4-14
4-14
4-14
4-14
4-15
4-15
4-15
4-15
5-1
5-2
5-2
5-4
5-4
5-4
5-5
5-5
5-6
5-8
5-9
5-9
5-10
5-10
5-12
5-13
5-13
5-13
Contents (2)
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Fig. No.
Page
Replacement of Main PCB 5-14
Fitting Optional Frequency Standard Unit 5-15
Fi tti ng Battery Pock (Opti on) 5-16
Fitting LF Frequency Multiplier
Assembly (Option) 5-17
IN TEXT ILLUSTRATIONS
Page
Al
3.1
3.2
3.3
3.4
4.1
4.2
4.3
4.4
5. 1
Table No.
1
2
3
4
5
6
7
8
9915
Vol. 2
Data Sequence Diagram
Basic Frequency Meter
Mul tiplex Display System
D.
1. L. Resi stor Array
Control Sequence Diagram
Theoretical P. I. N. Diode Attenuator
-5V Stabilizer
Battery Charging Circuit
Battery Power System
Mains Voltage Selection
LIST OF TABLES
Title
Data Output Connector
Time Base Selection Code
Signal Gating Paths
Test Equipment Required
Segment Check
Self Check Readout
'B' Input
Sensitivity Check
'A' Input Sensitivity Check
Tech. Spec. (8)
3-1
3-3
3-4
3-5
4-3
4-11
4-12
4-13
5-3
Page
Tech. Spec. (6)
T ech. Spec. (7)
4-5
5-1
5-5
5-6
5-7
5-8
Contents (3)
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SECTION 3
PARTS LISTS, COMPONENT LAYOUTS AN D CIRCUIT DIAGRAMS
Component Layout: Display Assembly
Parts List 1: Display Assembly'
Circuit and Layout: Oscillator PCB Assembly
Parts List 2: Oscillator PCB Assembly
Parts List 3: Chassis, Front and Rear
Panel Assemblies
Fig. 1
Fig. 2
SECTION 4
9915 Vol. 2
Parts List 40 and 4b: Main PCB Assembly
Component Layout: Main PCB Assembly Fig. 3
Circuit: 'A' Input Amplifier Fig. 4
Circuit: Main PCB and Display Assemblies Fig. 5
Parts List 5: LF Multiplier Assembly
Circuit and Layout: LF Multiplier Assembly (Option) Fig. 6
APPEND'CES AND CHANGE INFORMATION
APPENDIX 1: 0 PTION 01
SERIAL- TO- PARALLEL IN TERFACE UN IT
Contents (4)
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DISPlA Y
Format:
Latch:
Display Time:
Reset:
Check
Gate/Charging
Indi eator:
Overflow /Standby
Indicator:
Eight digit in-line LED 7 segment numerical display
pI
us overflow i nd: cator. Deci ma I pei nt posi ti oned
automati eally.
Previous measurement is displayed during period
required
to complete new measurement. Display is
updated automati col Iy at end of each measurement.
Approximately equal
to gate time plus 1 ms.
A biased Check/Operate/Reset Swi tch resets the
reodi ng to zero when pressed to Reset cnd re leased.
With Check/Operate/Reset Switch in Check position
display reads:-
Channel A - Al Idigi ts set to 8 to check all segments.
Channel B - Counter reads 1 MHz to check operation.
LE Dill um i noted when gate is open or batteri es are
being charged.
LED ill umi nates on overflow or when standby is
selected,
Battery Low Indi cator:
Overload Indi cator:
INPUT 'A'
Frequency Range:
Sensitivity:
Signal Range:
Input Impedance:
9915Vol. 2
LED indicates when botteries require recharging.
LED indicates when 'A' channel input exceeds about
5V r.m,s.
40 MHz to 520 MHz.
Better than 10 mV.
10 mV to
5V r.m.s. with automatic gain control.
500 nominal.
Tech. Spec. (1)
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IN PUT 'A' (Cont'd.)
Overload Protection:
P re$ca ling:
AGe:
Frequency Range:
Sens iti vi ty:
Input Impedance:
Maximum Input Levels:
(Damage Overload
Levels)
FREQUi:NCY MEASUREMENT
Range:
Accuracy:
Gate Times:
Resolution:
Burst Mode:
LF Multiplier Facility:
9915 Vol. 2
Up to 35V r. m. s. maximum by p. j . n. diode anenuotor
and reed relay.
Input frequencies are prescaled by a factor of ten.
50 dB minimum range. AGe output is available at
two pins on rear panel.
10 Hz to 60 MHz.
Better than 10 m V. Ad justable by front ponel control.
1
MD in parallel with 25 pF.
250V r.m.s. up to 10 kHz.
50V r. m. s. up to 100 kHz.
lOV r. m, s. above 100 kHz.
400V d.e.
Channel 'A' 4{) MHz to 520 MHz (prescaled by 10).
Channel 'B' 10 Hz to 60 MHz (direct).
±1 count ± frequency standord accuracy.
o.01 s, O. 1s, 1. Os I1 Os .
Channel 'A': 1kHz, 100 Hz, 10 Hz, 1Hz.
Channel '13': 100 Hz, la Hz, 1 Hz, O. 1Hz.
In the Burst Mode the gate remains closed until
tri ggered by i ncomi ng signal. After measurement
the display is held until manually reset.
The minimum signal duratIon is 30 ms plus gate time.
See Option 09.
T ech. Spec. (2)
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FREQUENCY STANDARD
Frequency:
Ageing Rate;
Temperature Stabi Ii ty:
AI ternative Standards:
STANDARD FREQUENCY
OUTPUT
Frequency
Level:
Waveform:
EXT ER NAL 5T AND ARD I NP LIT
Frequency
Minimum Level:
Maximum Ll~vel:
I:nput Impedance:
DATA OUTPUTS
Display:
POWER REQUIREMENTS.
Supply:
Vo I toge Ranges (a. c .) :
5 MHz.
±1 part in 10
6
per month .
±8 parts in 1 O~ over temperature range 00C to +55
0C.
±3 parts in 10 over temperature range +20
0C
to +40
0C.
See Options 04A and O,~,B.
1 MHz.
Standard TTL output.
Approximatel y rectongul ar.
1MHz.
500 mV r. m.S •
1 av r. m. s. 400 Vd. c .
Approximately 2000(0.c. coupled).
Serial BeD output is provided at stondard TTL logic
levels giving 8 digits and decimal points. Static
timebose and overflow output with timing controls
ore provided. Refer to Table 1 on page Tech Spec.
(6) .
94V to 265\/ r. m.s. I 45 to 450 Hz a.c. or optiona I
battery pack.
Eight ranges selected by transformer connection and
link:-
Consumption;
9915 Vol. 2.
94V to l06V
106V to 119V
118V to 132V
188V to 212V
19VA opproximal·ely.
200V to 225V
212V to 239V
223V to 251V
235V to 265V
Tech.Spec. (3).
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