HP 415E Service manual

MODEL 415E
SWR METER
SERIALS PREFIXED: 719-
See Appendix I and II at rear of manual for:
a) 415E Options 01, 02, and
b) Serials Prefixed 530-, 545-

Model 415E
Lists of Illustrations and Tables
OF ILLUSTtATi
Number Title Page
1- 1 . Model 415E SWR Meter. 1-0
2- 1 . The Combining Case. 2-0
2-2. Steps to Place Instrument in
Combining Case. 2-0
2-3. Adapter Frame Instrument
Combinations. 2-1
2- 4. Two Half Modules in Rack Adapter . . 2-2
3- 1 . Front Panel Operating Controls
and Connector. 3-2
3-2. Rear Panel Operating Controls
and Connectors. 3-2
3-3. Typical SWR Measurement Setup ... 3-3
3-4. General Turn-On Procedure. 3-4
3-5. Expanded Section of Figure 3-6 ... 3-5
3-6. Converting Decibels to SWR. 3-6
3-7. Attenuation Measurement Setup ... 3-6
3-8. Impedance Measurement Rules
Summary. 3-7
3-9. Shift of Minimum with Load and Short . 3-7
3-10. Example for Use of Smith Chart ... 3-8
3-11. 415E Noise Figure Curves .3-10
3-12. Meter Noise Correction Curve .... 3-10
LIST OF
Number Title Page
1-1. Specifications. . . . . 1-0
3-1.
Panel Descriptions.
. . . . 3-3
5-1. Recommended Test Equipment . . . . . . 5-1
5-2. Performance Tests.
. . . . 5-3
5-3. Etched Circuit Soldering
Equipment.
. . . . 5-8
Number Title Page
4- 1 . Block Diagram. 4-1
5- 1 . Test Set Up. ! . '!!!!! 5-3
5-2. Examples of Diode Marking
Methods. 5-9
5-3A. Switch Component Location.5-10
5-3B. Switch Component Location.5-10
5-4. Transistor Biasing and Operating
Characteristics.5-12
5-5. Power Supply Waveforms (AC
Operation Only.5-14
5-6. Power Supply Waveforms (Initial
Battery Operation - Only).5-15
5-7. Signal Flow Waveforms (Input to
Amplifier Output).5-16
5-8. Meter and Output Waveforms .... 5-17
5-9. Schematic Notes.5-18
5-10. Circuit Board Component
Location.5-19
5-11. Power Supply and Input Circuit . . . . 5-19
5-12. Output and Meter Circuit.5-21
1-1. Battery - Cover Assembly. 1-1
I- 2. Connector Assembly. 1-1
II- l. Circuit Board Component Location-
Instruments Prefixed 530 . II-1
Number Title Page
5-4. Out-of-Circuit Transistor Resistance
Measurements. 5-12
5- 5. Ohmmeter Ranges for Transistor
Resistance Measurements. 5-12
6- 1 . Reference Designation Index. 6-2
6-2. Replaceable. 6-8
6-3. Code List of Manufacturers. 6-11
iii
02152-3

Section I Model415E
Figure 1-1 and Table 1-1
Figure 1-1. Model 415E SWR Meter
Table 1-1. Specifications
Sensitivity: 0.15 pv rms at maximum bandwidth
(1 pv rms on high impedance crystal input).
Noise: At least 7.5 db below full scale at rated sen¬
sitivity and maximum bandwidth with input termi¬
nated in optimum source impedance (see Input).
Noise figure less than 4 db.
Range: 70 db in 10 and 2 db steps.
Accuracy: ±0.05 db/10 db step; maximum cumula¬
tive error between any two 10-db steps, ±0.10 db;
maximum cumulative error between any two 2-db
steps, ±0.05 db. Linearity: ±0.02 db on expand
scales, determined by inherent meter resolution on
normal scales.
Input: Unbiased low and high impedance crystal (100
and 5000 ohm optimum source impedance respec¬
tively); biased crystal (1 v into IK); low and high
current bolometer (4.5 and 8.7 ma ±3% into 200 ohms),
positive bolometer protection. Input connector, BNC
female.
Input Frequency: 1000 cps, adjustable 7%. Other
frequencies between 400 and 2500 cps available on
special order.
Bandwidth: Variable, 15 to 130 cps. Typically less
than 0. 5 db change in gain from minimum to maxi¬
mum bandwidth.
Recorder Output: 0 to IV, 1000 ohms source imped¬
ance, BNC female.
Amplifier Output: 0to0.3Vrms (NORM), 0to0,8rms
(EXPAND) into at least 1 OK ohms, dual banana jacks.
Meter Scales: Calibrated for square-law detectors.
SWR: 1 to 4, 3.2 to 10 (NORM); 1 to 1.24 (EXPAND).
DB: 0 to 10 (NORM); 0 to 2.0 (EXPAND). Battery:
charge state.
Meter Movement: 0.25% movement, taut-band sus¬
pension, mirror-backed scale with expanded db and
swr scales greater than 4-1/4 in. (108 mm) long.
Power: 115 or 230 volts ±10%, 50to 400cps, 2watts.
Power line frequency or multiples thereof must not
be at the tuned amplifier frequency. Optional re¬
chargeable battery provides up to 36 hours contin¬
uous operation.
Dimensions: 7-25/32 in. wide, 6-3/32 in. high, llin.
deep from front side rail (190 x 155 x 279 mm).
Weight: Net 7-7/8 lb (3, 5 kg), 9-7/8 lb (4, 4 kg) with
battery.
Options:
01. Rechargeable battery installed.
02. Rear-panel input connector in parallel with the
front-panel connector.
1-0
02152-2

Model 415E
Section I
Paragraphs 1-1 to 1-7
SECTION 1
GENERAL INFORMATION
1-1. INTRODUCTION.
1-2. The Model 415E SWR Meter is a high-gain ampli¬
fier, tuned to an audio frequency, with a square-law
calibrated meter readout. The Model 415E is designed
for use with square-law detectors in the measurement
of SWR and attenuation. In addition, because of the
high-sensitivity and tuned amplifier, it can be used as
a null detector for audio frequency bridges. The Model
415E is shown in Figure 1-1. Operating Specifications
for the Model 415E are given in Table 1-1.
1-3. The Model 415E is a tuned audio amplifier de¬
signed to operate at a mean center frequency of 1000 cps
(Hz), adjustable 7% with a variable bandwidth of from
15 to 130 cps (Hz). Operating center frequency and band¬
width are both variable at instrument front panel.
Tuned amplifier gain is only slightly changed due to
any change in bandwidth and is typically less than 0.5 ab.
In addition to the front panel meter readout provided
by the SWR Meter, two rear panel outputs are also
available: An AC amplifier output is provided to allow
using the 415E as a high-gain (126 db) tuned amplifier;
a DC recorder output providing a convenient means of
obtaining a permanent record of measurement data.
Either or both of these rear panel outputs can be used
without affecting instrument meter operation provided
power line ground is not connected to the instrument
through either rear panel connector.
1-4. INSTRUMENTS COVERED BY MANUAL.
1-5. This manual applies directly to the Model 415E
SWR Meters having serial numbers prefixed 719 (first
three numbers of serial number). If the serial prefix
on your instrument is other than 719, there are differ¬
ences between the manual and your instrument which
are described in a Manual Changes sheet included with
the manual. If the manual changes sheet is missing,
the information can be supplied by your nearest Hewlett-
Packard Sales and Service Office (see lists at the rear
of this manual). The manual change sheet may also
include an "ERRATA” section which describes manual
correction information which applies to the manual for
all instruments including instruments prefixed 719.
1-6. INSTRUMENT OPTIONS.
1-7. This manual provides operating and servicing
information for the standard Model 415E. In addition,
operating and servicing information for Model 415E
instruments with Options 01 and/or 02, described be¬
low, is also included.
a. Option 01: Factory installed, 24-volt recharge¬
able battery capable of supplying up to 36 hours con¬
tinuous operation of the Model 415E. If not initially
installed as an option, the same battery is available
on order from Hewlett-Packard (see Paragraph 2-17).
b. Option 02: Additional input connector on rear
panel wired in parallel with the front panel INPUT con¬
nector. If not initially installed as an option, the con¬
nector - cable assembly is available on order from
Hewlett-Packard (see Paragraph 2-17).
02152-4
1-1

Section II
Figures 2-1 and 2-2
Model 415E
Figure 2-1. The Combining Case
[twist divider to vertical
POSITION
INSERT DIVIDER, ENGAGING
TABS IN TOP AND BOTTOM
MOUNTING SLOTS
©
GING
TOM
-OTS
©
PUSH IN TO LIMIT
©
SLIDE LATCH TO LOCK
DIVIDER
n—.
. *
/ g”T asL~" CE
,L=S===1
\\
=> aS> t ™ . \
PUSH RETAINER DOWN
TO RELEASE
©
TO SET RETAINER BACK IN
PLACE, ENGAGE HOOKS FIRST
ON ONE SIDE OF DIVIDER,
THEN ON OTHER
®
PUSH RETAINER UP TO LOCK
Figure 2-2. Steps to Place Instrument in Combining’Case
2-0
02152-1

Model 415E
Section II
Paragraphs 2-1 to 2-16
SECTION II
PREPARATION FOR USE
2-1. INCOMING INSPECTION.
2-2. This instrument was inspected both mechanically
and electrically before shipment. To confirm this, the
instrument should be inspected for physical damage in
transit. Also check for supplied accessories, and test
the electrical performance of the instrument, using
the procedure outlined in Paragraph 5-3. If there is
damage or deficiency, see the warranty on the inside
front cover of this manual.
2-3. INSTALLATION.
2-4. The Model 415E is fully transistorized; therefore
no special cooling is required. However, the instru¬
ment should not be operated where the ambient tem¬
perature exceeds 55 °C (140°F).
2-5. RACK MOUNTING.
2-6. The Model 415E is a submodular unit that when
used alone can be bench mounted only. However, when
used in combination with other submodular units it can
be bench and/or rack mounted. The hp combining case
and adapter frame are designed specifically for this
purpose.
2-7. COMBINING CASE. The combining case is a
full-module unit which accepts varying combinations
of submodular units. Being a full-module unit, it can
be bench or rack mounted analogous to any full-module
instrument. An illustration of the combining case is
shown in Figure 2-1. Instructions for installing the
Model 415E in a combining case are given graphically
in Figure 2-2.
2-8. ADAPTER FRAME. The adapter frame is arack
frame that accepts any combination of sub-modular
units. It can be rack mounted only. An illustration of
the adapter frame is given in Figure 2-3. Instructions
are given below:
a. Place the adapter frame on edge of bench as shown
in step 1, Figure 2-4.
b. Stack the sub-modular units in the frame as shown
in step 2, Figure 2-4. Place the spacer clamps be¬
tween instruments as shown in step 3, Figure 2-4.
c. Place spacer clamps on the two end instruments
(see step 4, Figure 2-4) and push the combination into
the frame.
d. Insert screws on either side of frame, and tighten
until sub-modular instruments are tight in the frame.
e. The complete assembly is ready for rack mounting.
2-9. THREE-CONDUCTOR POWER CABLE.
2-10. To protect operating personnel, the National
Electrical Manufacturers’ Association (NEMA) rec¬
ommends that the instrument panel and cabinet be
grounded. All Hewlett-Packard instruments are
equipped with a three-conductor power cable which,
when plugged into an appropriate receptacle, grounds
the instrument. The offest pin on the power cable
three-prong connector is the ground wire.
2-11. To preserve the protection feature when oper¬
ating the instrument from a two-contact outlet, use a
three -prong to two-prong adapter and connect the green
pigtail on the adapter to ground.
2-12, PRIMARY POWER REQUIREMENTS.
2-13. The Model 415E can be operated from an AC or
DC primary power source. The AC source can be either
115 or 230 volts, 50 to 400 cps. The DC source is a
24-volt rechargeable battery. The rechargeable bat¬
tery is supplied with option 01 instruments only.
2-14. For operation from AC primary power, the in¬
strument can be easily converted from 115- to 230-
volt operation. The LINE VOLTAGE switch, SI, a
two-position slide switch located at the rear of the in¬
strument, selects the mode of AC operation. The line
voltage for which the instrument is set to operate ap¬
pears on the slider of the switch. A 1/16-ampere, 250
volt fuse is used for both 115- and 230-volt operation.
CAUTION
DO NOT CHANGE THE SETTING OF THE
LINE VOLTAGE SWITCH WHEN THE IN¬
STRUMENT IS OPERATING.
2-15. INITIAL BATTERY CHECK.
2-16. The following applies to option 01 instruments
or instruments that have field - installed batteries.
When the battery is used as the power source for the
first time, perform the following steps:
Figure 2-3. Adapter Frame Instrument Combinations
02152-1
2-1

Section II
Paragraphs 2-17 to 2-20
Model 415E
©
ADAPTER
FRAME
Figure 2-4. Two Half Modules in Rack Adapter
a. Connect Model 415E to AC source. Set POWER
switch to CHARGE and charge battery for a minimum
of 16 hours or overnight. Note: the battery can be
maintained in the charging state indefinitely without
damaging the battery. It will assume its full capacity,
1.25 ampere hour, and no more.
b. Set POWER switch to TEST position, the meter
needle indication should be within the”BAT. CHARGED”
area (see Figure 3-1).
2-17. INSTALLING BATTERY AND INPUT
CONNECTOR.
2-18. Available from Hewlett-Packard are parts re¬
quired for modifying any Model 415E to correspond to
those instruments with Option 01 and/or Option 02. A
rechargeable Battery Installation Kit, hp Part Number
00415-606, contains the battery and necessary hard¬
ware for installation (corresponds to Option 01). In¬
stallation instructions are detailed in Appendix at rear
of this manual. To obtain the parts required for an
input connector on the rear panel (corresponding to
Option 02), order by hp Part Number as found in Table
6-1 (listed under Option 02). Instructions for instal¬
lation of this additional connector are detailed in Ap¬
pendix at rear of this manual.
2-19. REPACKAGING FOR SHIPMENT.
2-20. When returning an instrument to the Hewlett-
Packard Company, use the original packing material
(if foam type) if available or contact an authorized hp
Sales Office for assistance. If this is not possible, first
protect the instrument surfaces by wrapping in heavy
Kraft paper or with sheets of cardboard flat against
the instrument. Then protect the instrument on all
sides (use approximately 4 inches of packing material
designed specifically for package cushioning), pack in
a durable container, mark container clearly for proper
handling, and insure adequately before shipping.
Note
When an instrument is being returned to the
Hewlett-Packard Company for service or re¬
pair, attach a tag to the instrument specifying
the owner and desired action. All correspon¬
dence should identify the instrument by model
number and the full (eight-digit) serial number.
2-2
02152-1

Model 451E Section III
Paragraphs 3-1 to 3-14
SECTION I!!
OPERATING INSTRUCTIONS
3-1. INTRODUCTION,
3-2. This section contains information and procedures
for operation of the Model 415E (from either AC or bat¬
tery power source) in making swr and attenuation
measurements. Also included is information on slotted
line techniques, instruction in the use of a Smith Chart
for plotting load impedance, and discussion of Model
415E noise performance with various source imped¬
ances and noise effect on meter indication.
3-3. FRONT AND REAR PANEL FIXTURES.
3-4. Figures 3-1 and 3-2 identify by number the front
and rear panel fixtures of the Model 415E. The des¬
criptions in Table 3-1 are keyed by number (1-12 for
front, 13-18 for rear) to the figures. Further infor¬
mation regarding the various settings and uses of the
controls, indicators, connections, and adjustments is
included in the procedures of this section. Information
on battery is found in Paragraph 3-6.
3-5. GENERAL OPERATING AND
MEASUREMENT CONSIDERATIONS.
3-6. BATTERY OPERATION.
3-7. The Model 415E may be operated from a battery
instead of the 115 or 230 volt AC supply (see Paragraph
2- 13). Battery operation requires some slightly dif¬
ferent procedures to prolong battery life and to ensure
proper results. The rechargeable nickel - cadmium
battery is factory installed if ordered as Option 01 (see
Paragraph 1-7). The same battery may be ordered
and installed later. To obtain this, order hp Stock
Number 00415-606, Rechargeable Battery Installation
Kit.
3- 8. INITIAL BATTERY USE. When the Model 415E
is to be battery operated for the first time, perform
the following steps:
a. Switch the Model 415E POWER switch to BAT-
TERY/TEST position and note meter pointer indication:
A meter pointer indication in the "BAT. CHARGED"
area indicates the internally battery properly charged
and ready for use: A meter pointer indication to the
left of the "BAT. CHARGED" area means that the
battery must be charged as described below.
b. Connect the Model 415E to AC power source. Set
POWER switch to BATTERY/CHARGE and charge the
battery for a minimum of 16 hours or overnight.
c. After at least 16 hours of recharge time, switch
POWER switch to BATTERY/TEST position and check
battery charge. If the battery charge indication is still
unsatisfactory, see Paragraph 5-35.
3-9. OPTIMUM BATTERY USAGE. It is recommended
that the Model 415E be operated by the battery for up
to 8 hours, followed by 16 hours of recharge. If con¬
tinuous battery operation is required for more than 8
hours, the recharge time should be double the oper¬
ating time. Continuous battery operation is possible
for up to 36 hours but this must be followed by a pro¬
longed recharge period.
3-10. BATTERY STORAGE. Storage of the battery at
or below room temperature is best. Extended storage
at high temperatures will reduce the cell charge but
not damage the battery if the storage temperature is
less than 140°F. It is suggested that the battery be
charged after removal from storage and before using
the Model 415E for battery operation.
3-11. GROUNDLOOP CURRENTS .
3-12. The 415E SWR Meter audio amplifier has high
sensitivity to low level signals. To reduce ground loop
currents, the 415E grounds are isolated by a 46.4 ohm
resistor. Ground loops occur when instruments are
connected to415E outputs and grounded through power
cords or rack mountings. Ground loops can be min¬
imized in the following ways:
a. Connect the 415E to instruments with floating-
inputs;
b. Connect the 415E to instruments with high input
impedance; Connect only the signal wire between in¬
strument and the 415E;
c. Operation at higher signal levels;
d. An Adapter on the power cord to float the instru¬
ment ground where not prohibited by safety regulations.
3- 13 . BANDWIDTH AND FREQUENCY SELECTION.
3-14. Two front panel adjustments are provided to op¬
timize operation of the Model 415E tuned amplifier.
The FREQ (frequency) control allows a total variation
of 7% of the center tuned frequency. When more than
one Model 415E is included in the same measurement
setup, the variable tuned frequency is used to set all
the instruments to the exact frequency modulating the
source. The high sensitivity and narrow bandwidth
of the amplifier make the Model 415E valuable as a
meter-indicating null detector for audio frequency
bridges. The BANDWIDTH adjustment varies the tuned
filter bandwidth from 15 to 130 cps. A narrow band¬
width is best for low level signals as this improves
the signal to noise ratio. A wide bandwidth would find
more use in fast sweep rate measurements.
02152-4
3-1

Section HI
Figures 3-1 and 3-2
Model 415E
4I5E-A-9
Figure 3-1. Front Panel Operating Controls and Connector
Figure 3-2. Rear Panel Operating Controls and Connectors
3-2
02152-1

Model 415E
Section in
Paragraphs 3-15 to 3-21
Table 3-1. Panel Descriptions
1. Selects desired 415E power source:BATTERY/
CHARGE position allows internal battery re¬
charge when power cord is connected to AC line,
2. Indicator lights when power switch is in LINE/
ON or BATTERY/CHARGE position.
3. Female BNC INPUT connector.
4. Set input of Model 415E for use with a bolom¬
eter or crystal detector mount. See Paragraph
3-53.
5. Adjustment allows center frequency variation
by 70 cps.
6. Attenuator adjusts gain in 10 db steps.
7. Allows full scale expansion of any 2.0 db portion
of the 10-db scale.
8. Changes bandwidth from 15 to 130 cps.
9. Allows initial meter reference setting with a
control range of at least 10-db.
10. Provides fine adjustment of GAIN control meter
settings.
11. Mechanical zero adjustment allows exact sett¬
ing of meter needle to 2.0 db calibration mark.
12. With POWER switch set to BATTERY/TEST, a
meter needle indication within the ’’BATTERY
CHARGE” area on the meter face (indicated by
12A) shows that internal battery is charged suf¬
ficiently for proper 415E operation; if needle
indicator is to left (area 12B) of "BATTERY
CHARGED” area, then battery is not charged
sufficiently for proper instrument operation
(option 01 - ONLY).
13. Additional input connector (wired in parallel
with front panel connector); supplied as Option
02 for 415E only upon request.
14. DC output for recorder use (0 to 1 volt into open
circuit or 1000 ohms).
15. AC output for use as tuned amplifier output.
16. Three-conductor AC power cord receptacle
(NEMA-type).
17. Contains power line fuse.
18. Slide switch to allow 115- or 230-volt AC
operation.
3-15. SWR MEASUREMENT EQUIPMENT
AND TECHNIQUES.
3-16. EQUIPMENT .
3-17. A typical setup of equipment used in SWR meas¬
urements is shown in Figure 3-3. The signal source is
usually square-wave modulated at 1000 cps since other
modulating waveforms often cause undesirable fre¬
quency modulation of the source. Harmonics from the
source sometimes cause trouble and can be eliminated
with a low-pass filter.
3-18. The detector should be a square-law device (out¬
put voltage proportional to RF power input) such as a
barretter or a crystal diode operated at low signal
levels. The meter of the 415E is calibrated for square-
law detectors. Crystal diodes are normally more sen¬
sitive than barretters but barretters are square-law
over a wider dynamic range. Both types of detector
normally maintain accurate square-law response up to
at least full scale deflection with the RANGE-DB switch
set to 30 position and coarse GAIN at maximum. (1 mv
RMS sine wave or 2.2 mv peak-to-peak square wave
causes full scale deflection on HIGH XTAL IMPED
position. On other positions of INPUT switch, 0.15 mv
RMS sine wave or 0.33 mv peak-to-peak square wave
causes full scale deflection.) Above this level these
detectors should be individually checked for departure
from square-law behaviour or manufacturer’s data
should be consulted.
02152-3
3-19. A short circuit termination is useful in establish¬
ing reference positions along the transmission line and
is measuring transmission line wavelengths.
3-20. SLOTTED LINE PROBE PENETRATION .
3-21. A general rule in slotted line measurement is to
use minimum probe penetration that still picks up ad¬
equate signal to measure. The probe couples to the
Figure 3-3. Typical SWR Measurement Setup
3-3