Serial No.
THIS DOCUMENT CONTAINS INFORMATION PROPRIETARY TO WAVETEK. THE INFORMATION IN THIS DOCUMENT IS NOT TO BE USED OR DUPLICATED IN ANY MANNER WITHOUT THE PRIOR APPROVAL, IN WRITING OF WAVETEK.
66 N. 1ST AVENUE, P.O. BOX 190 BEECH GROVE, INDIANA 46107 317-783-3221
1/80
SECTION GENERAL INFORMATION
1.1 INTRODUCTION
The WAVETEK MODEL 2000 Sweep/Signal Generator offers programming, versatility and an exceptionally wide frequency range (1 to 1400 MHz) in a rugged, compact instrument. It is well adapted to both sophisticated laboratory applications and automatic production testing.
Each of its three frequency ranges (1-500 MHz, 450-950 MHz, and 900-1400 MHz) may be used in either △F or CW mode of operation. It can be swept at any rate from 50 sweeps per second to 1 sweep every 100 seconds. Sweep width ranges from 200 kHz to 500 MHz. Manual, triggered, or recurring sweeps are provided, and the center frequency, sweep width, and output level may all be controlled by external voltages.
Up to six crystal-controlled birdy marker modules (single frequency or harmonic type) may be plugged into the Model 2000. Each module has its own front-panel on/off switch. Front-panel amplitude and width controls enable optimum adjustment of the marker display. In application.
the markers may be tilted up to 90° for easy viewing when displayed with steep transition signals, or rectified for X-Y plotter applications by an internal switch. An optional 1 kHz modulator provides square wave modulation of the RF output for low-level recovery applications.
Most optional features, as well as the functional circuits for the basic sweep generator, have modular plug-in construction. This allows optional features to be factory installed at the time of purchase, or customer installed at a later date. This concept offers protection against obsolesence, since updated and additional features can be simply and economically added as new test procedures dictate.
Maintenance problems can be greatly simplified by stocking several modules instead of hundreds of discrete components. Servicing time of a defective instrument can be cut to a fraction of the time previously required, and can be performed by relatively inexperienced technicians. Modules for the Model 2000 are stocked in Wavetek service centers around the world.
1.2 SPECIFICATIONS
1.2.1 RF OUTPUT
Frequency Range -
Frequency Dial Calibration – Accuracy –
Vernier Frequency Control -
Spurious Signals –
Residual FM --
Drift -
Blanking –
Amplitude -
Flatness at +10 dBm -
Impedance –
1.2.2 SWEEP SPECIFICATIONS
Operating Modes -
Sweep Modes -
Sweep Time -
Sweep Width -
Display Linearity -
Horizontal Output -
1 to 1400 MHz in three overlapping bands: 1 to 500 MHz, 450 to 950 MHz, 900 to 1400 MHz
10 MHz intervals ±10 MHz or 2% of selected frequency, whichever is greater
±5 MHz
≥ -26 dBc from 10 to 1400 MHz
<15 kHz peak to peak
< 100 kHz/5 minutes; 2 MHz/8 hours (after 1/2 hour warm-up at a constant ambient, and allowing a 5 minute stabilizing period after a frequency change).
Retrace blanking of the RF output provided for sweep operation. Removed for CW operation.
Continuously adjustable from +10 to -80 dBm 70 dB in 10 dB steps 20 dB vernier - calibrated in 1 dB steps
Step Attenuator Accuracy ±0.5 dB to 500 MHz ±1 dB to 1000 MHz ±2 dB to 1400 MHz
Vernier Accuracy ±0.5 dB to 500 MHz ±1 dB to 1000 MHz ±2 dB to 1400 MHz
±0.5 dB from 1 to 1400 MHz when read with negative detector. ±0.75 dB from 20 to 1400 MHz when read with RF power meter.
50 ohms standard, 75 ohms optional
NOTE: Slight degradation of Amplitude Accuracy and Flatness specifications may occur at frequencies above 1000 MHz on 75 ohm instruments. Output controls are calibrated in dBmV with maximum output being +57 dBmV.
CW, ∆F
Repetitive sweep, single sweep, externally triggered sweep, manual sweep, line-lock sweep.
Continuously variable from less than 10 ms to more than 100 seconds in 4 decade steps, plus vernier.
200 kHz to 500 MHz
2%
16 Vpp (symmetrical about ground)
1.2.3 REMOTE PROGRAMMING
Frequency -
Sweep Width -
0-20 dB Output -
External FM -
External AM -
1.2.4 EXTERNAL LEVELING
External Monitor (ALC) -
1.2.5 MARKERS
Туре —
Accuracy -
External Marker Input -
Marker Width -
Marker Size -
Rectified Birdy -
Marker Tilt -
The rear-panel REMOTE jack provides necessary connections for remote control of frequency, sweep width and the 0 to 20 dB OUTPUT vernier range. This jack also provides connections for external amplitude and frequency modulation.
May be remotely programmed by a ±16 volt signal (-16 volts corresponds to low frequency band end and +16 volts to high frequency band end).
May be controlled by a remote potentiometer.
May be remotely programmed over a 20 dB range with a 0 to -18 volt signal (-18 volts corresponds to maximum output).
The full frequency range can be swept at rates up to 4 kHz. With reduced deviation and linearity, modulation rates up to 100 kHz are possible.
External AM signals are applied to the same connections as for 0-20 dB Output control; therefore, OUTPUT vernier range must be restricted so the 0 to -18 volt range is not exceeded or distortion will occur. With average voltage set to mid-range, 100% modulation is obtainable up to a 1 kHz rate, 40% modulation is obtainable up to a 40 kHz rate.
An external negative signal, between 0.2 and 2 volts, may be used to level the RF output. The front-panel ALC input jack mates with a 9/64" dia. x 9/16" long miniature phone plug (Switchcraft 750 or equivalent). When the external monitor plug is installed, the internal ALC loop is disabled.
Birdy by-pass. Provision for 6 plug-in marker modules plus rear-panel external marker input. Markers may be either single frequency or harmonic (comb) type. (See Options A-1 and A-2.)
0.005%
Rear-panel BNC connector accepts external CW signal for conversion to a birdy marker, Input level: 100 mV into 50 ohms.
Adjustable from ~15 to 400 kHz in four steps.
Adjustable from ~1 Vpp to 1 mVpp.
Internal switch removes the negative portion of the birdy marker for use with X-Y recorders. Size varies with detector's impedance. Adjustable from ~ 6 volts to 1 mV with detector impedance of 1 megohm, or from ~0.5 V to 1 mV with detector impedance of 0 ohms.
Provides horizontal markers with size equal to approximately 10% of horizontal display. Adjustment of MARKER SIZE control vectorily adds the normal vertical marker to the horizontal marker, causing the resulting marker to vary from a horizontal position toward a vertical position.
1.2.6 GENERAL
| Power Requirements | 115/230 VAC ±10% (approximately 20 W) 50-60 Hz. | |
|---|---|---|
|
Dimensions (including screw heads,
knobs, and feet) |
14.3 cm (5 5/8 in.) high
34.9 cm (13 3/4 in.) deep 20.9 cm (8 1/4 in.) wide |
|
| Weight |
20 lbs. net
25 lbs. shipping |
|
| 1.3 | OPTIONS | |
| A-1 | Single Frequency Marker at any frequency between 1 and 1400 MHz. | |
| A-2 | Harmonic Marker at 1, 10, or 50 MHz (other frequencies available on special order) intervals. | |
| A-4 | Square Wave Modulator provides blanking of RF output at 1 kHz rate. | |
| A-5 | Pen Lift provides contact closure during forward sweep. | |
| 1.4 | ACCESSORIES | |
| 1.4.1 | FURNISHED WITH INSTRUMENT | Instruction Manual |
| Spare plug with pins for remote programming (mates with REMOTE jack). | ||
| 1.4.2 | AVAILABLE AT EXTRA COST |
Wide Band Detectors:
D151 (50 ohms, up to 1000 MHz) D152 (50 ohms, up to 1400 MHz) D171 (75 ohms, up to 1000 MHz) |
| Service Kit (K102) containing module extender and RF extension cables. | ||
| Rack Mount Kit (K103) mounts single instruments into 19 inch rack (see Section 2.2.3). | ||
| Rack Mount Kit (K104) mounts one or two instruments into 19 inch rack (see Section 2.2.4). |
Image Test module (M112B) enables checking the image rejection of a tuner.
SECTION 3 OPERATING INSTRUCTIONS
3.1 INTRODUCTION
This section provides complete functional control description, operating instructions, and programming instructions for the Wavetek Model 2000. In addition, special operating notes cover sweep rate errors, overloading, low-level measurements and operation with networks analyzers and X-Y plotters.
3.2 DESCRIPTION OF FRONT PANEL
Refer to Figure 3-1.
(1) BAND switch selects desired frequency band; 1 to 500 MHz, 450 to 950 MHz or 900 to 1400 MHz.
(2) FREQUENCY controls adjust center frequency of sweep (or CW frequency). Outer dial is coarse adjustment. Inner knob is vernier adjustment, providing ~ ±5 MHz fine tuning about the center frequency set by the coarse control. (Coarse control is calibrated when vernier is aligned with indicator.)
(3) OUTPUT step control provides calibrated adjustment of the RF output in 10 dB increments from +10 dBm to -60 dBm.
(4) OUTPUT vernier provides 20 dB vernier adjustment of the RF output calibrated in 1 dB increments.
(5) MARKER push-button switches activate the various marker options installed in the instrument as indicated on the individual buttons. If Option A-4 is installed, the bottom button will control that option.
(6) POWER switch applies AC power to the Power Supply. Pilot light indicates operation.
(7) SWEEP TIME control provides selection of sweep time, manual sweep control, and triggered sweep. Outer dial selects MANUAL, LINE, and four ranges of variable
sweep time. Inner knob (VAR/MANUAL) provides manual sweep control when outer dial is set to MANUAL, and vernier control of sweep time when outer dial is set to one of the four variable ranges. Triggered sweep may be set (only in the four variable ranges) by pulling the inner knob (PULL/TRIG) out.
(8) TRIGGER push-button manually triggers a single sweep when the SWEEP TIME control is set for triggered sweep operation.
(9) SWEEP WIDTH control logarithmically adjusts the displayed sweep width from less than 200 kHz to more than 500 MHz when the slide switch is in the 500 MHz position. When the switch is in the 100 or 10 MHz position, the maximum sweep width is reduced as indicated. Full counterclockwise rotation of the control will switch the instrument into CW operation.
(10) MARKER WIDTH control adjusts marker display. Outer knob selects one of four marker widths from 15 to 400 kHz in four steps. Inner knob controls marker size, and, when pulled out, activates the marker tilt feature. When the marker tilt is activated, full counterclockwise rotation of the control will provide horizontal markers with an amplitude of approximately 10% of the total horizontal display. Clockwise rotation will produce a varying amount of tilt toward the vertical axis.
(11) RF OUT connector (BNC) provides connection for the RF output signal.
(12) DEMOD IN connector (BNC) accepts the demodulated swept signal from the device under test so that RF markers may be added. (The combined signal is available at the rear-panel SCOPE VERT connector.
(13) EXT ALC IN jack accepts an automatic leveling control signal from a remote monitor and disconnects the internal ALC loop. (See Section 1.2.4.)
Figure 3-1. Front Panel
3.3 DESCRIPTION OF REAR PANEL
Refer to Figure 3-2.
(1) AC LINE SWITCH enables unit to operate from either 115 VAC or 230 VAC supply mains.
(2) AC LINE cord provides connection to AC mains via 3 prong plug.
(3) AC LINE FUSE is time-delay; 0.5 amp for 115 VAC operation, 0.25 amp for 230 VAC operation.
(4) REMOTE jack and plug provide connections for remote control of center frequency, sweep width, external AM, external FM, and RF output level.
(5) SCOPE HORIZ connector (BNC) provides a -8 to +8 V triangle wave for driving the display oscilloscope horizontal channel.
(6) SCOPE VERT connector (BNC) provides the vertical display signal (demodulated signal plus markers if DEMOD IN is used) for the display oscilloscope.
(7) EXT MARKER connector (BNC) accepts an external CW signal to produce a marker at the external frequency on the display.
(8) PEN LIFT (Option A-5) binding posts provide contact closure during forward sweep when the frontpanel SWEEP TIME control is in the 10-100 sec. position. In all other ranges, and during retrace, the contacts are open.
NOTE
In MANUAL sweep, the contacts are continually closed.
3.4 TYPICAL OPERATING SET-UP
When initially setting up the instrument, first check the rear-panel AC LINE SWITCH and FUSE to ensure the instrument is set for operation with the available AC mains.
Make connections between the sweep generator, the device under test, and the oscilloscope as shown in Figure 3-3. Since hum, RF leakage, and spurious signal pick-up must be kept to a minimum, it is essential that good connections and grounds be maintained throughout the entire set-up. Use coaxial cables with BNC connectors wherever possible. The RF output cable is especially critical. It should match the output impedance of the sweep generator and should be kept as short as practical (under 3 feet). If the input impedance of the device under test is not the same as the sweep generator output impedance, a matching network
should be used to ensure a constant amplitude input signal to the device under test (see Figure 3-3).
After the RF signal passes through the RF circuit of the device under test, it must be demodulated before being connected to the sweep generator DEMOD IN connector. If a demodulator is not a part of the device under test, one must be added externally (see Figure 3-3). The input impedance of the demodulator must present the proper load to the RF circuit being tested. The Wavetek Models D151 and D152 RF Detectors are recommended for 50 ohm applications, while the Model D171 is for 75 ohm applications.
Turn the POWER switch on. The pilot light should light, indicating an operating condition.
NOTE
This instrument does not require a warmup period unless it is to be used at the extreme limits of its specifications.
After completing the set-up, adjust the sweep generator controls for the required center frequency, sweep width, output amplitude, and sweep rate. Turn the desired markers on and adjust their size and width.
3.5 SPECIAL OPERATING NOTES
3.5.1 SWEEP RATE EFFECTS
When sweeping RF circuits having rapid amplitude changes, errors may occur, due mainly to detector delays. Decreasing the detector output time constant will minimize this effect. Figure 3-4 illustrates sweep rate effect.
To check for sweep rate effect, first set the sweep width to its lowest practical amount, then reduce the sweep time while closely observing the swept output response. Any change in the response indicates the sweep rate is too fast for a true response. When a further reduction of the sweep time does not change the response, a true response has been obtained.
3.5.2 EFFECTS FROM OVERLOADING
The use of excessive input signals to the device under test can cause overloading. To assure that this condition is not present, and that the response is a true representation of the device under test, set the OUTPUT controls for minimum output amplitude. Gradually increase the output amplitude until a response is obtained. Further increasing the output amplitude should not change the configuration of the response envelope except in amplitude. If the response envelope does change, such as flattening at the top, decrease the output just far enough to restore the proper configuration.
Figure 3-4. Sweep Rate Effects
Figure 3-5. Leveling
Figure 3-6. REMOTE Jack
3.5.3 LOW-LEVEL MEASUREMENTS
When making measurements at low levels, radiation and ground loops become problems. Using double-shielded cables for cables carrying RF signals helps minimize the radiation problems. Ground loops causing hum pick-up can sometimes be eliminated by completing only one ground connection between each instrument. This applies particularly to the scope horizontal input. If the ground connection is made at the vertical input terminal, an additional ground at the horizontal input terminal will often result in hum pick-up.
3.5.4 OPERATION WITH X-Y PLOTTERS
Two features are incorporated into the sweep generator to facilitate operation with X-Y plotters. First, a Plotter switch converts the high-frequency marker signals to lower frequencies which are compatible with the operating speed of the plotter pen. This is an internally operated switch, located directly behind the front-panel DEMOD IN connector, and is accessible by removing the instrument bottom cover.
A second feature, available as Option A-5, provides a contact closure during sweep time to operate the plotter's pen-lift mechanism. This feature operates only when the SWEEP TIME selector switch is set to its slowest (100 to 10 SEC) position and during manual sweep.
3.5.5 OPERATION WITH NETWORK ANALYZERS
To operate properly with certain network analyzers, several modifications might be required. Some analyzers require the removal of the blanking signal during the sweep retrace. This can be accomplished by disconnecting the single wire connected to pin 10 of the M1H module. Another modification sometimes required is to provide a horizontal output ramp that varies from zero to some positive voltage instead of the standard –8 to +8 volt ramp. This can be accomplished by connecting a 56 kohm resistor between pins 2 and 11 of the M1H module. This connection provides a horizontal output signal of approximately 0 to 10 volts.
3.5.6 OPERATION WITH EXTERNAL MONITOR
Operation with an external monitor can produce a flatter (less amplitude variation) input signal to the device under test than is obtainable with the internal monitor. The external monitor point is located at the point where greatest flatness is desired, and is not affected by cable VSWR or the input impedance of the device under test. Another application is to level at the output point of a wide-band power amplifier in order to increase the output power capability of the sweep generator.
To operate with an external monitor, set the output controls for maximum and connect the output from the external monitor to the front-panel ALC IN connector.
The signal from the external monitor must be of negative polarity between 0.2 and 2 volts. If the signal is larger than 2 volts, use a resistive divider to obtain less than 2 volts. While observing the output from the monitor on an oscilloscope, adjust the OUTPUT vernier control until the monitor signal becomes leveled (refer to Figure 3-5).
3.6 PROGRAMMING
Connections for remote control of output amplitude, frequency, and sweep width, plus external AM and FM and triggering of the sweep circuit are provided by a rearpanel REMOTE programming connector. The programming jack is shown in Figure 3-6. The pin functions are listed below.
VOLTAGE AND SIGNAL SOURCES
- Pin 1 Ground
- Pin 2 +16 volts
- Pin 3 -16 volts
- Pin 4 -18 volts
- Pin 10 Ramp for Driving Sweep Width Control
- Pin 15 Same as Pin 10 Except Inverted
CONTROL INPUTS
Pin 6 – Output Level Control (Ext AM)
- Pin 7 Sweep Time Trigger Input
- Pin 9 Frequency Control
- Pin 12 Sweep Width Control (Ext FM)
INTERNAL CONTROL
Pins 5, 8 and 11 are used to program internal operation of amplitude, frequency and sweep width.
UNUSED Pins 13 and 14 are unused.
3.6.1 OUTPUT AMPLITUDE CONTROL (EXT AM)
Normal internal control is provided by a jumper wire connected between pins 5 and 6 of the REMOTE plug.
To provide external control, remove the jumper wire and connect an External Output control as shown in Figure 3-7. The RF OUTPUT is a linear function of the programming voltage as shown in Figure 3-8.
To provide external AM, connect as shown in Figure 3-9. The low frequency modulation will be limited by the reactance of capacitor C1. Lower frequency modulation, down to DC, can be provided with a modulating source having a DC offset. In this case, resistor R1 is omitted. In all cases, the peak modulating voltage plus the DC offset must be within the limits of -18 to +2 volts, as shown in Figure 3-8, or distortion will occur. The modulation frequency limits the maximum useable percentage of modulation as shown in Figure 3-10. This graph was obtained with the DC level set to -8 volts.
Figure 3-9. External AM
3.6.2 FREQUENCY CONTROL
Normal internal control of frequency is provided by a iumper wire between pins 8 and 9 of the REMOTE plug.
To provide external control, remove the jumper and connect pin 9 to an External Frequency control as shown in Figure 3-11. Tuning sensitivity, which is approximately 16 MHz/volt, is shown graphically in Figure 3-12.
3.6.3 SWEEP WIDTH CONTROL (EXT FM)
Normal internal control of sweep width is provided by a jumper wire between pins 11 and 12 of the REMOTE plug.
To provide external control, remove the jumper and connect pin 12 to an External Sweep Width control as shown in Figure 3-13.
To provide external FM, connect as shown in Figure 3-14 and turn the front-panel SWEEP WIDTH control fully ccw. The modulating waveform should have an average potential of 0 V. Frequency sensitivity is shown graphically in Figure 3-15. The maximum modulating frequency, while
still maintaining this sensitivity, varies from approximately 4 kHz at maximum deviation to 20 kHz for 1 MHz deviation (see Figure 3-16). With decreased frequency sensitivity, frequencies up to 200 kHz can be used, as shown in the shaded area of Figure 3-16.
NOTE
The peak amplitude of the modulating signal plus the DC voltage supplied by the External Frequency control (REMOTE plug pin 9) should not exceed ±16 V. To do so would program the instrument to sweep beyond its frequency band limits.
3.6.4 REMOTE TRIGGERING OF SWEEP TIME CIRCUIT
The sweep time circuit can be remotely triggered by applying a 10 volt positive pulse to pin 7 of the REMOTE plug. For proper operation, the front-panel SWEEP TIME selector must be set for one of the four variable sweep time positions, and the PULL TRIG knob pulled out. The repetition rate of the external trigger should be slower than the frequency running rate set by the front-panel SWEEP TIME selector and VAR/MANUAL control.
Figure 3-11. External Frequency Control
Figure 3-13. External Sweep Width Control
Figure 3-14. External FM
Figure 3-15. FM Deviation/Modulation Frequency
SECTION 4 CIRCUIT DESCRIPTION
4.1 INTRODUCTION
This section first presents an overall block diagram analysis followed by a more detailed description of each module.
Before beginning the actual circuit description, it would be well to consider the mechanical arrangement of the instrument. This will enable the following block diagram and circuit description to be associated with its physical position, thereby providing a better understanding of the overall instrument. The mechanical arrangement can be seen by referring to Figure 5-14.
4.2 FUNCTIONAL BLOCK DIAGRAM
The block diagram in Figure 4-1 contains both block and module information. The blocks contained within each module are indicated by the module outline.
The Power Supply provides three regulated voltage sources of +18, -18, and -20 volts for connection to the plug-in modules.
The M1H module generates the sweep ramp, blanking, and scope horizontal voltages.
The M2J module contains three distinct circuits; a -16 volt reference supply, a +16 volt reference supply, and the sweep drive circuits.
The two reference supplies and the sweep ramp voltage provide the signals to the front-panel FREQUENCY and SWEEP WIDTH controls. The signals from these controls are then fed to the M2J Sweep Drive module, where they are combined into a single signal which drives the frequency-determining varactor diodes in the M9H and M19H Sweep Oscillator modules. Necessary level shifting, shaping, and amplitude control are performed in the M2.
The RF signal for band 1 (1 to 500 MHz) is generated in the M9H module where the signals from two sweep oscillators are combined in a diode mixer. The resultant difference signal is fed to a 1-500 MHz preamplifier and then to the M10H Amplifier module. This module contains a voltage-variable attenuator (VVA) and the final 1-500 MHz amplifier. The output from this amplifier is fed to the
M19H module where a PIN diode switch completes the circuit to the RF output.
Leveling of the RF output is accomplished by a monitor diode which measures the RF voltage and compares it to a reference voltage supplied by the OUTPUT vernier control. Any error between the two voltages is amplified in the leveler amplifier located in the M10H module. The error voltage is then connected to the voltage-variable attenuator (VVA) at the input of the final 1 to 500 MHz amplifier. This closed-loop system maintains a constant-amplitude RF signal at the monitor point, which compensates for amplitude variation in the sweep oscillator, mixer, and amplifier circuit, and also creates a zero impedance at the monitor point. In order to create a 50 ohm source impedance, a 50 ohm resistor is connected between the zero impedance point and the RF output system.
The sweep oscillators for bands 2 and 3 are located in the M19H module. The RF output from the appropriate oscillator is fed through a voltage-variable attenuator directly to the RF output circuit without amplification. Leveling for bands 2 and 3 is accomplished in the same manner as for band 1.
The marker circuit is comprised of the M5H Marker Adder module and the individual M6 Marker modules. In addition to the marker adding function of the M5H module, it also provides for selection and leveling of the sweep sample signal in the same manner as the main RF output signal was leveled. This provides a constant-amplitude sweep sample signal to the individual marker modules, which is extremely important for obtaining a "flat comb" output from the harmonic generating marker modules. It also standardizes the sweep sample amplitude in all instruments, ensuring proper operation of field-installed markers.
This constant-amplitude sweep sample signal is fed to the individual M6 Marker modules where it is combined in a mixer with a crystal-controlled CW signal. The resultant difference signal, which is the birdy marker, is then fed back to the Marker Adder module where it is combined with other birdy markers, shaped, and amplified into a single composite signal. This signal is then fed through the MARKER SIZE control and to the rear-panel SCOPE VERT connector.
Figure 4-1. Block Diagram
THE FOLLOWING CIRCUIT DESCRIPTIONS ARE REFERENCED TO THE SCHEMATICS APPEARING IN SECTION 7.
4.3 POWER SUPPLY (PS6)
The PS6 Power Supply provides three regulated voltages and the optional Pen Lift circuit.
AC POWER AND RECTIFIER CIRCUITS
A dual-primary transformer allows operation at a line voltage of either 115 or 230 volts. AC power is supplied through a 4 wire receptacle from the front-panel POWER switch. The transformer is located away from the Sweep Drive module to reduce magnetically-coupled line ripple. Unregulated plus and minus voltages are supplied by two full-wave rectifier circuits and filtered by capacitors C1 and C7. A 12-pin plug, mounted to the printed circuit board, provides access to three unregulated voltages as well as the regulated +18, -18, and -20 V supplies. This plug also accepts a scope horizontal signal for connection to a rear-panel connector. The Pen Lift switching circuit is also enabled through this plug.
PEN LIFT
Installation of K50 and rear-panel jacks provides a contact closure occuring during sweep time. Transistor Q11 is normally conducting from current supplied through pin 9 of the 12-pin plug. When the base drive to transistor Q11 is removed, the relay is energized by the turn-on of transistor Q12. To prevent early failure of the relay contacts, the relay is energized only during slow sweep speeds and in the MANUAL position of the front-panel SWEEP TIME selector.
+18 V SERIES REGULATOR
Regulation is provided by IC1, which contains its own internal reference supply. Resistor R9 provides an adjustment for +18.00 V. An external pass transistor, Q2, boosts the current capability, and transistor Q1 improves the current-limiting characteristics of IC1 by providing amplification before limiting. The +18 V supply is protected against reverse voltage by diode CR7.
-18 V SERIES-SHUNT REGULATOR
The voltage reference for this supply is obtained from the +18 V supply through resistor R20. Resistor R19 provides feedback, applied to IC2, which provides high gain, forcing transistor Q5 to maintain a shunt-regulated voltage across resistor R13. Transistors Q3 and Q4 provide the series-pass element, and are connected as a compound emitter follower so that the voltage across resistor R13 is not loaded heavily. Short-circuit protection of transistor Q5 is provided by diode CR8. Current limiting is provided by transistor Q5 when transistor Q6 conducts sufficiently to forward bias diodes CR9 and CR10. Reverse-voltage protection is provided by diode CR12.
20 V SERIES REGULATOR
The reference voltage for the -20 V supply is applied to a differential amplifier, transistors Q9 and Q10, which controls the conduction of series-pass transistor Q8.
Diode CR17 provides reverse-voltage protection. Current limiting is provided by the shutting down of the -18 V supply by transistor Q7 through diode CR14 to the base of transistor Q5, reducing the reference voltage to the base of transistor Q9. This action is helped along by the conduction of diode CR13 if the -20 V supply drops below -18 V.
4.4 SWEEP RATE (MODULE M1H)
SWEEP RATE GENERATOR
This module generates variable rate square and triangular waveforms. Front-panel switching provides recurring, triggered, or manual modes. The triangular waveform is a 32 Vpp signal with a sweep time variable from 10 msec to 100 seconds in four steps, with retrace time held constant at the fastest sweep time of each range. The triangular waveform is also used to provide the sweep drive and scope horizontal signals.
The square wave output is a -1 to +15 V signal whose -1 V level corresponds to the sweep time and whose +15 V level corresponds to the retrace time. The square wave is used to provide blanking of the RF output during retrace.
The triangular waveform is generated in an integrator, transistors Q1, Q2, Q3, and Q4, by applying positive and negative voltage levels to the integrator input. When the integrator positive ramp output exceeds a threshold voltage, a bi-stable hysteresis switch is switched, reversing the polarity of the integrator input, causing the triangular waveform to start down toward another threshold. If the module is programmed in a recurring mode, the negative ramp will trip the hysteresis switch output is clipped on the negative polarity, and is used for blanking (pin 10).
The symmetrical square wave output from the hysteresis switch (pin 9) is connected, through the front-panel SWEEP TIME VAR/MANUAL control and one of the range determining resistors of the SWEEP TIME selector switch, to the integrator input (pin 7). Since the integrator output voltage change is proportional to the input voltage level, the SWEEP TIME VAR/MANUAL control provides a sweep time increase by reducing the hysteresis switch output if the polarity is negative. If the polarity is positive, full output is retained (a diode opens the VAR/MANUAL ground connection), producing a nearly constant retrace time.
For triggered modes, the negative threshold of the hysteresis switch is shifted out of the way by diode CR5 and resistor R47 connected through transistor Q14, or
through switch S102d, when in LINE position. The integrator will now continue its negative ramp until it is stopped by a clamp circuit turned on by a comparator. The integrator output is now held at this level unless a trigger is applied to the hysteresis switch. A trigger cannot flip the hysteresis switch until this clamp level is reached because the triggers must pass through an amplifier which is gated off until the clamp comparator transistor (Q9) conducts.
Triggers are prevented from reaching the hysteresis switch (pin 6) by +18 V at pin 1, which causes comparator transistor Q8 to open FET switch Q14. The primary function of the voltage at pin 1 is to shift the clamp comparator input out of the way to allow free-running oscillation.
Since the integrator is an inverting amplifier, and both input (pin 7) and output (pin 8) are available, a feedback resistor network allows the SWEEP TIME VAR/MANUAL control, R102, to be used as a DC level shifter in the MANUAL mode. A non-inverting amplifier, consisting of transistors Q6, Q7 and Q19, with a gain of 2, provides a 32 Vpp triangle wave output which is used for sweep drive. This output is divided by resistors R18 and R53 to provide a horizontal drive of 16 Vpp to an impedance of approximately 23 kohms.
A Centering adjustment resistor (R41) provides a DC level adjustment of the integrator and horizontal outputs (pin 8, pin 12, and pin 11) by shifting both positive and negative thresholds of the hysteresis switch. A Size adjustment resistor (R45) provides an amplitude adjustment by effectively varying the size of the hysteresis window. Symmetry of trace and retrace time (for equal positive and negative input voltages to the integrator) is established by adjusting the Integrator Balance control resistor R7. This adjustment also affects the MANUAL mode centering and the sweep period for fully counterclockwise rotations of the SWEEP TIME VAR/MANUAL control.
The five sections of the SWEEP TIME selector switch program the M1H module. The functions of each section are listed below:
Section a - Integrator input selector
Section b — Clamp level shift and routing switch disconnect Section c — Triager source selector
Section d — Line trigger routing and hysteresis switch hold Section e — Pen Lift enable
Circuit operation as modified by the switch positions may be understood by considering the VARIABLE, MANUAL, and LINE positions one at a time.
VARIABLE RATE POSITIONS
Section a – Proper integrator input resistors are selected in decade increments in these positions, R105 – R108. 4-4
Section b – The clamp is disabled and triggers are held off unless the PULL TRIG switch is opened, removing +18 V.
Section c – Two trigger sources are connected to pin 4; an external trigger from REMOTE jack pin 7 and front-panel momentary TRIG switch S103.
Section d – No connection is made in any of the variable rate positions.
Section e – When in the 100-10 SEC position, the negative hysteresis switch output activates the Pen Lift option during forward trace. During retrace, the positive hysteresis switch output biases the circuit off. In the other variable rate positions, +18 V keeps the Pen Lift circuit deactivated.
MANUAL POSITION
Section a – A feedback resistor, R113, is connected from the output (pin 8) to the input (pin 7) of the integrating amplifier, converting it to an inverting DC amplifier. Resistor R114 shifts the amplifier output DC level to -8 V for zero input voltage to resistor R104. When the SWEEP TIME VAR/MANUAL control, R102, is fully clockwise, the negative input voltage to R104 is sufficient to shift the output voltage to +8 VDC.
Section b — The clamp is disabled in this position by applying +18 V to pin 1, causing the hysteresis switch input to be disconnected from any internal source of triggering by opening the routing switch transistor, Q14 (since transistor Q8 is turned off). The shift bias is disconnected when transistor Q14 is open.
Section c - The trigger input point, pin 4, is grounded.
Section d – The hysteresis switch is held in one state by applying -18 V to its input through a 33 kohm resistor, R111. This causes the output to be negative (this bi-stable circuit is a positive feedback amplifier), providing the proper polarity to resistor R102 and preventing blanking of the RF output.
Section e – The negative hysteresis switch output provides base drive for the Pen Lift option through resistor R112.
LINE POSITION
Section a – The proper value integrating resistor is selected, by-passing the SWEEP TIME VAR/MANUAL control, to produce equal sweep and retrace periods.
Section b – Clamping works in this position independent of the PULL TRIG switch.
Section c - The line rate sine wave from the Power Supply (J2 - pin 3) is connected to the trigger input (pin 4).
Section d — Amplified triggers are routed into the hysteresis switch independent of the internal routing transistor, Q14, providing additional line rate reliability.
Section e – In the LINE position, +18 V through resistor R113 keeps the Pen Lift circuit deactivated.
4.5 SWEEP DRIVE (MODULE M2J)
The M2J module provides the correct sweep drive voltage required by each oscillator as programmed by the frontpanel FREQUENCY and SWEEP WIDTH controls and the BAND switch.
These programs are summed to a standard voltage level and fed to shaping circuits for each band which are enabled by the B-1, B-2, and B-3 voltages.
The shaping diodes conduct at levels determined by a variable resistor network driven by a constant current source, transistor Q4.
As each diode conducts, an additional current is fed into the summing junction of the output amplifier consisting of transistors Q8, Q9, and Q10.
The output waveform amplitude is controlled by resistors R42, R44, and R46, which are connected by FET switches Q11, Q12, and Q13 into the feedback path to the summing junction.
This module also provides two regulated voltages (±16 V) for use primarily as programming voltages.
4.6 SWEEP OSCILLATOR, BAND 1 (MODULE M9H)
The RF sweep signal for band 1 is developed by the hetrodyne method which utilizes two UHF sweep oscillators, a diode mixer, and a wide band RF amplifier.
Sweep oscillator transistor Q2 sweeps from approximately 1.4 to 1.65 GHz. The average frequency is adjusted by resistor R2, which controls the average bias on the varactor diodes, CR1, CR2, and CR3. The sweep drive voltage from pin 9 of the module is connected to the opposite side of these diodes, causing the frequency to vary from low to high.
The circuit for sweep oscillator transistor Q5 is similar to the Q2 circuit; however, the varactor diodes have been reversed and the polarity of the bias voltage supplied by Cent adjustments R12 (coarse) and R13 (fine) have been changed. These changes cause the oscillator frequency to vary from high to low. The approximate output frequency is 1.4 to 1.15 GHz. This out-of-phase sweep technique has several advantages. First, larger sweep widths are obtain-
able, and second, the nonlinearity (frequency versus time) of one oscillator is cancelled by the nonlinearity of the second oscillator. Resistor R9, which is a linearity adjustment, optimizes this cancelling process by controlling the sweep drive ratio between the oscillators.
The two sweep signals are combined in a single-balanced diode mixer comprised of inductors L4 and L5 and diodes CR8 and CR9. The resultant difference frequency of 0 to 500 MHz is then amplified in the wide band amplifier consisting of transistors Q11, Q12, and Q13.
Transistors Q6 and Q7 supply the blanking voltage to the wide band amplifier and cause it to be shut off during the sweep retrace. The output from the wide band amplifier is connected to J1, which, in turn, is connected to the M10H Output Amplifier. A second output is also obtained from this amplifier and is coupled, via resistor R45, to a similar wide band amplifier consisting of transistors Q14, Q15, and Q16. The output from this amplifier is connected to J2, which, in turn, is connected to the marker generating circuits.
Transistors Q8, Q9, and Q10 provide a -15 V supply to operate the sweep oscillators. This improves stability and provides isolation between the oscillators and the -18 V supply.
4.7 OUTPUT AMPLIFIER, BAND 1 (MODULE M10H)
The M10H module contains a wide band amplifier, a voltage-variable attenuator, and a leveler amplifier.
WIDE BAND AMPLIFIER
This amplifier provides 2 stages of RF amplification to increase the RF input level present at transistor Q1 by about 40 dB.
The frequency response of this amplifier is reduced for frequencies below 0.5 MHz and above 500 MHz.
The input amplifier stage, consisting of transistors Q1 and Q2, is enabled by the B+1 switching voltage. The output stage, consisting of transistors Q3, Q4, Q5, and Q6, is enabled by -20 V when the front-panel BAND switch is set for band 1. The -20 V also provides current through resistor R30 and the RF output cable to turn on a PIN diode, located in the M19H module, which couples the band 1 RF output into the Output Step Attenuator.
VOLTAGE-VARIABLE ATTENUATOR
Ahead of the first RF amplifier is a voltage-variable attenuator consisting of PIN diodes CR1, CR2, and CR3 which provides variable RF conductance proportional to the positive current supplied through switching transistor Q7.
LEVELER OUTPUT (PIN 6)
Leveler amplifier transistors Q9, Q10, and Q11 provide leveling of the RF output for bands 1, 2, and 3 by supplying a positive current to the voltage-variable attenuator system for each band as directed by band switching voltages B-1, B-2, and B-3. These voltages turn on the correct switching transistor for that band in the M10H or M19H module.
A positively increasing output voltage from the leveler amplifier will increase the RF output level. RF blanking is effected by a positive input voltage (pin 4) to switching transistor Q8 which causes the leveler output (pin 6) to go negative during sweep retrace time, shutting off the voltage-variable attenuator.
LEVELER INPUTS (PINS 5 AND 7)
A monitor diode, located in the M10H, provides a negative DC voltage related to the RF output level present in the output system. This negative voltage is connected to one input of the operational amplifier, consisting of transistors Q9, Q10, and Q11.
Since an increasingly negative voltage at the input will reduce the positive current supplied to each voltage-variable attenuator, the RF output level is held constant, by negative feedback, at a level determined by a reference voltage. This reference voltage varies under control of the level program input voltage at pin 7. The magnitude of this negative voltage is determined by the Level Max control which sets the maximum RF level when the program voltage a small negative reference voltage which determines the minimum RF level when the level program voltage at pin 7 is 0 V.
4.8 SWEEP OSCILLATOR, BANDS 2 AND 3 (MODULE M19H)
This module contains two sweep oscillators with their voltage-variable attenuators and the necessary switching circuitry to connect either band 1, band 2, or band 3 to the common monitor and Output Step Attenuator.
The band 1 output is connected to the RF output circuit by PIN diode CR9. The control current for switching this diode comes from the M10H module.
The band 2 oscillator, consisting of transistor Q6 and its associated circuitry, is a common base oscillator, varactortuned by diodes CR2, CR3, CR4, and CR5.
Biasing of the varactor diodes is provided by transistors Q1 and Q2. Q3 is a switching FET which disconnects the bias voltage from the varactors when the instrument is operated in band 1 and band 3. The B- voltage for the oscillator is modulated by the blanking signal from pin 4
in transistor stages Q4 and Q5. This modulation causes the oscillator to be cut off during the sweep retrace period, thereby providing a zero RF output level during the retrace time. The RF signal from the oscillator is coupled via inductor L9 to a voltage-variable attenuator consisting of diodes CR6, CR7, and CR8. This attenuator is part of the closed-loop leveling system consisting of monitor diode CR20, the leveler amplifier (located in the M10H module), and the voltage-variable attenuator. The operation of this circuit maintains a constant-amplitude RF signal at the monitor point, and also allows adjustment of this signal over a 20 dB range. Since the effective impedance at the output impedance at approximately 50 ohms.
The band 3 oscillator is almost identical to that for band 2. The oscillator tank inductance has been decreased and the oscillator transistor, Q14, is operated at a slightly higher current. The varactor bias is provided by Q9 and Q10 and the B- blanking is provided by Q11 and Q12. Current during the sweep retrace time is not completely removed, but is steered by Q13 through CR12. This current will not cause oscillation since L15 has been bypassed. It does, however, provide better frequency stability in the oscillator. The RF signal from the oscillator is coupled via L20 through the voltage-variable attenuator consisting of CR17, CR18, and CR19 to the Output Step Attenuator.
Q7 and Q8 help provide the proper bias to the shunt diodes in the voltage-variable attenuators in order to maintain a constant load for the oscillators, thus minimizing the frequency-pulling effects of the attenuators.
Switching transistors Q15 and Q16 connect the output of the leveling amplifier to the voltage-variable attenuator associated with the operating band.
4.9 MARKER ADDER (MODULE M5H)
The main function of this module is adding together and amplifying the individual marker signals from the M6 Marker modules. It also contains the external marker mixer circuit and the sweep sample selection and leveling circuits.
The desired sweep sample signal (band 1, 2, or 3) is selected by PIN diode switch CR4 and CR5. The sweep sample signal is then leveled in the same manner as the main RF output signal. The voltage from monitor diode CR7 and the reference voltage from resistor R46 is fed to the leveling amplifier consisting of transistors Q12 and Q13. Transistor Q11 provides blanking of the leveling amplifier. Any error between the two input signals is amplified and fed to voltage-variable attenuator CR6. The operation of this circuit produces a constant-amplitude signal at the monitor point.
The leveled sweep sample signal is connected to the external marker mixer, CR1 and CR2, and to the sweep sample output connector, J4. A 47 ohm resistor, connected between J4 and the monitor point, establishes the source impedance at approximately 50 ohms. The signal is then routed to each M6 Marker module.
The marker output signals from the individual M6 Marker modules are connected to the input pins 1, 2, 3, and 4 of the M5H module. One or two M6 outputs are connected to each input. The signals are then amplified in the input stages, transistors Q2, Q3, Q4, and Q5, and combined in the common collector load. The collector load is an external 10 mH choke (L101) when the front-panel MARKER WIDTH selector is set to WIDE. or a 3.3 kohm resistor (R21) when the selector is set to NARROW. The combined marker signals are then amplified in transistor stages Q6, Q7, and Q8. The front-panel MARKER WIDTH selector also varies the high-frequency gain of the amplifier by connecting capacitance across R27, the feedback resistor. The amplified signal is then fed to the complimentary output stage, transistors Q9 and Q10, which is biased so that input signals less than 0.5 V are not amplified. This eliminates most spurious markers and noise from the output. The output is then connected through the frontpapel MARKER SIZE control to the rear-papel SCOPE VERT connector.
4.10 MARKERS (MODULES M6)
Several types of marker modules are available to cover the frequency range of the Model 2000, and to produce single frequency and harmonic markers. These include:
| M6S | SINGLE FREQUENCY | (Option A1) |
|---|---|---|
| M6H | HARMONIC | (Option A2) |
| M66H | DUAL HARMONIC | (Option A2) |
SINGLE FREQUENCY
Single Frequency Markers produce one birdy marker at any specified frequency of the sweep generator. Each module
contains a crystal oscillator, a mixer and a birdy amplifier. The various crystal oscillators employed can produce CW signals of from 1 to 55 MHz. For marker frequencies greater than 55 MHz, harmonics of the crystal frequency are used.
The output from the crystal oscillator (or harmonic generator, if used) is combined with the mixer. The mixer includes a tuned circuit which selects the frequency from which the birdy is generated. A zero beat occurs when the sweep sample frequency equals that of the CW signal from the crystal oscillator (or harmonic generator). The difference frequency around the zero beat is amplified by the birdy amplifier, which has a bandwidth of less than 800 kHz, thus producing the marker.
INDIVIDUAL AND DUAL HARMONIC
Harmonic Markers produce birdy markers at evenly spaced intervals across the sweep generator frequency range. The crystal oscillator, operating between 1 and 55 MHz, sends a signal to a harmonic generator. The comb produced by the harmonic generator is combined with the instrument sweep sample in the mixer, which is untuned. This produces a series of zero beats at intervals equal to the crystal oscillator frequency. The mixer output is amplified by the birdy amplifier, which has a bandwidth of less than 800 kHz, thus producing the birdy markers.
In the Dual Harmonic Markers, the same process as above is employed to generate the birdy markers, except that a portion of the crystal oscillator output is sent to a countdown divider. The divider output is used to produce markers at 1/N the crystal frequency, where N is the divider factor. Thus two sets of markers (in phase with each other) are produced.
For harmonic markers with a greater-than-55 MHz interval, the crystal oscillator is set up to produce a strong second harmonic of the crystal frequency. The fundamental is filtered out, and the harmonic frequency is sent to the harmonic generator.
section 5 maintenance
5.1 INTRODUCTION
This section provides information for testing, calibrating, and troubleshooting the sweep generator. The performance test is designed for incoming inspection and periodic evaluation. If performance is not to specifications, refer to the calibration and troubleshooting sections.
5.2 SERVICE INFORMATION
5.2.1 DISASSEMBLY INFORMATION
REMOVAL OF BOTTOM COVER – Remove the two rear feet (A) and lift cover off with a slight rearward movement.
REMOVAL OF TOP COVER – Remove the single screw (B) from the top and lift off cover with a slight rearward movement.
REMOVAL OF SIDE PANEL – Either side panel can be removed to provide better access by removing the four screws holding the side panel to the instrument. The frontpanel module section can be removed from the power supply section by removing two screws holding the sections together and by disconnecting the electrical connectors between the two sections.
NOTE
Separation of the two sections performs no useful purpose during normal service procedure.
5.2.2 MODULE SERVICING
SERVICE KIT K102 — This kit contains a module extender and RF extension cables which enable the module to be electrically operated while physically located above the rest of the modules, thereby making all parts easily accessible.
REMOVAL OF MODULES – Modules may be removed by removing any cables attached to the top of the module and removing the hold-down screw (C) from the bottom.
REMOVAL OF MODULE COVER – Remove all nuts and screws from top of module and slide the cover off.
REINSTALLING MODULE – Before reinstalling the module, check the module pins for proper alignment, then carefully seat the module pins into the chassis socket and
replace the hold-down screw (C) to ensure a good ground connection between module and chassis.
MODULE PIN NUMBERING SYSTEM – The module pins are numbered as shown in Figure 5-2. The index stud for each standard module is located off-center to prevent the module's being plugged in backwards. This off-center stud location also provides a method for locating pin 1.
5.3 PERFORMANCE CHECK
The following procedure is intended to ensure that the instrument meets its published specifications. The checks specified assume that the instrument is equipped with Option A-2 Harmonic Markers at 1 MHz, 10 MHz, and 50 MHz. While it is possible to check the instrument's performance without the use of harmonic markers by using suitable external CW sources, a complete check by this method is impractical. The required performance is shown in Section 1.2, Specifications.
5.3.1 TYPICAL SET-UP
Connect as shown in Figure 5-4. Adjust the instrument controls as follows:
| 0 - 500 | |
|---|---|
| 250 MHz | |
| 500 MHz | |
| +10 dBm | |
| LINE | |
| WIDE | |
| 50 HAR on | |
Adjust the scope to operate in an X-Y mode. Set the vertical sensitivity to 0.2 V/division. Adjust the scope vertical position, horizontal position and horizontal sensitivity, and the instrument MARKER SIZE control to obtain a scope pattern as shown in Figure 5-5.
5.3.2 DISPLAY LINEARITY, MAXIMUM SWEEP WIDTH AND FREQUENCY RANGE CHECK
Display linearity is read directly from the display shown in Figure 5-5. Each marker must fall within 0.2 divisions of its graticule line. This is equivalent to a display linearity of 2%. This 2% specification is extremely important since all dial accuracy specifications are directly related to it. Repeat this check on bands 2 and 3.
Figure 5-1. Disassembly
Figure 5-2. Module Pin Numbering
Table 5-1. Recommended Test Equipment
INSTRUMENT
CRITICAL REQUIREMENT
Oscilloscope
Digital Voltmeter
Power Meter
RF Detector
Spectrum Analyzer
Precision Attenuator Pads
Marker Generators
CW Signal Generator
DC Coupled; 1 mV/div Sensitivity
±0.1% Accuracy
Frequency Range 10 to 1400 MHz
50 ohm Impedance; Frequency Range 1 to 1400 MHz
Frequency Range 10 MHz to 3 GHz
10, 20, 40 dB
1, 10, 50 MHz Harmonic Markers
Adjustable to any frequency within the range of the instrument; 0.1 V output; ±10 MHz Accuracy
RECOMMENDED
TEK 5110/5A18N/5B10N
DANA 4200
HP 437A/8485A
WAVETEK D152
HP 8555A/8552A
WEINSCHEL 50-10, 50-20, 50-40
WAVETEK M6H-1, M6H-10, M6H-50
WAVETEK 2001
-
-
-
-
-
1
-
LM723C
Figure 5-3. Component Lead Configuration
To identify the frequencies shown on the display of Figure 5-5, one frequency or marker must be positively identified. All remaining frequencies can be identified by referencing this frequency. For band 1, the low-limit marker is not a marker but the zero lock-in produced by the heterodyne sweep generator technique. The frequency of each marker shown on the display can be identified by referencing the zero lock-in point. For bands 2 and 3, one frequency can be identified by using an external CW generator and the rear-panel MARKER IN connector. By referencing the marker produced by the known external CW signal, the exact frequency of each marker on the display is obtained. This also verifies operation of the external marker circuitry.
The maximum sweep width of 500 MHz is also read directly from the display of Figure 5-5.
Since the frequency indicated at the exact center of the display of Figure 5-5 is the same as the output frequency when the instrument is operated at minimum sweep width, the center frequency range of the instrument can be checked by simply turning the FREQUENCY control to its extremes and noting the range of frequencies indicated at the exact center of the display. The low and high limit markers should move past the display center line by approximately 1/2 division. This represents approximately 5% overrange capacity.
To verify low frequency, turn on the 10 MHz harmonic markers and adjust the FREQUENCY and SWEEP WIDTH controls to position the zero lock-in point on the extreme left scope graticule line and the first 10 MHz harmonic marker centered on the extreme right scope graticule line. Turn on the 1 MHz harmonic markers and, counting down from the 10 MHz marker, locate the marker which corresponds to 1 MHz.
The output must be flat (constant amplitude) down to the 1 MHz marker. This verifies the low-frequency limit.
5.3.3 DIAL ACCURACY CHECK
Dial accuracy is checked in a manner similar to the frequency range check just completed.
Set the FREQUENCY control to position the zero lock-in or the low limit harmonic marker to the center of the display. Reduce the sweep width to approximately 10 MHz to provide the necessary resolution. Turn the 50 MHz harmonic markers off and turn the 10 MHz harmonic markers on. Center the marker on the display with the FRE-QUENCY control.
NOTE
Make sure the indicator line on the FREQUENCY vernier
is aligned with the frequency indicator and remains in this position during the entire check.
Read the frequency error on the FREQUENCY dial. Allowable error is ±10 MHz or 2% of frequency, whichever is greater. Next, advance the FREQUENCY control until the next 10 MHz harmonic marker is centered on the display and again read the error on the FREQUENCY dial. Continue this process until the entire frequency range has been verified on all bands.
5.3.4 MINIMUM SWEEP WIDTH CHECK
The minimum sweep width of 200 kHz is verified as follows:
Turn the 1 MHz harmonic markers on. Adjust the FRE-OUENCY and SWEEP WIDTH controls to position a 1 MHz harmonic marker on the extreme left scope graticule line and the next higher 1 MHz harmonic marker on the extreme right scope graticule line. The scope horizontal is now calibrated for 1 MHz full scale or 100 kHz/division. Adjust the FREQUENCY control to center a 1 MHz harmonic marker on the scope display. Adjust the MARKER WIDTH control to produce a marker width slightly greater than 200 kHz. Since the marker presentation has sloping sides, it should be possible somewhere along its amplitude to locate a point where its width exactly equals 200 kHz For example, if the marker is 300 kHz wide at its base and 100 kHz wide at its peak amplitude point, it would be 200 kHz (2 divisions) wide at approximately its 50% amplitude point. Decrease the sweep width to minimum and ensure that the marker, at the amplitude point corresponding to 200 kHz, covers the entire scope display. Perform this check on all three bands.
5.3.5 MAXIMUM OUTPUT CHECK
Set the BAND switch to 0-500 and the FREQUENCY control to 300 MHz. Set the SWEEP WIDTH control for CW operation.
Set the OUTPUT controls for +10 dBm. Set the power meter to its +10 dBm range and connect the power meter's senor to the RF OUT connector. The power meter should read +10 dBm ±.5 dB.
5.3.6 FLATNESS CHECK
Set the sweep generator controls as in Section 5.3.1.
Decrease the scope's horizontal sensitivity to produce a display width of approximately 4 divisions. Increase the scope's vertical sensitivity and adjust the vertical position control until the display occupies exactly 10 divisions between the zero level retrace line and the maximum amplitude point. (Check all three bands to locate the maximum
Figure 5-5. Detected Display
Figure 5-6. Horizontal Output
amplitude point.) The minimum amplitude point (check all three bands) must be 8.9 divisions or more for a flatness
537 CW MODE CHECK
Adjust the SWEEP WIDTH control to its full counterclockwise detent. This position removes the return trace blanking and sweep drive from the oscillator. The output frequency is controlled by the FREQUENCY controls, and the accuracy is identical to the FREQUENCY dial accuracy check in Section 5.3.3. The output amplitude is the same as in the sweep mode of operation with the absence of the zero level retrace reference.
5.3.8 FREQUENCY DRIFT CHECK
Set the sweep generator controls as in Section 5.3.1 and calibrate the display width to 1 MHz. Position a marker to the exact center of the oscilloscope display and read frequency drift directly from the scope display by noting the change in the marker's position with time. Each division represents 100 kHz.
When reading drift over long periods of time, calibrate the display width to 5 MHz. Center a marker on the scope display and read drift as before, except each division now represents 500 kHz.
Maximum allowable drift is < 100 kHz/5 min, 2 MHz/8 hr.
5.3.9 RESIDUAL FM CHECK
Adjust the SWEEP WIDTH control to calibrate the display width to 1 MHz. Adjust the FREQUENCY control to center a 1 MHz harmonic marker on the scope display. Increase the horizontal sensitivity by a factor of ten. (Use the scope horizontal step control only and do not turn the horizontal vernier control, as this would change the calibration.) The display is now calibrated to indicate 10 kHz/division.
Residual FM can be read directly on the scope display by noting the amount of jitter of the marker.
Change the SWEEP TIME selector from LINE to the .1-.01 sec position and again read the marker jitter. Any additional jitter in this position represents the line-related residual. Maximum allowable jitter is 15 kHz peak to peak.
5.3.10 SPURIOUS SIGNAL CHECK
The only practical way to measure spurious signal content is with a high quality spectrum analyzer covering from 10 MHz to at least two times the upper frequency range of the instrument to be checked. The spurious signal check is
made in accordance with the instructions furnished with the particular spectrum analyzer being used.
Spurious signal content is ≥ -26 dBc from 10 to 1400 MHz instrument frequency.
NOTE
The heterodyning method of generating the output signal for band 1 will produce non-harmonically related spurious signals in addition to the harmonically related signals. These signals are typically -40 to -50 dBc up to 300 MHz, and at losst -26 dBc near the bird and of band 1
5.3.11 ATTENUATOR CHECKS
VERNIER
The accuracy of the vernier can be checked using the power meter while operating the instrument in CW mode. The initial set-up is the same as in Section 5.3.5. Once the maximum output has been checked, continue by reducing the OUTPUT vernier control in 1 dB increments until the minimum has been reached. The power meter reading at each 1 dB increment should be within 0.5 dB of the indicated output plus the error at maximum output. If desired, the vernier can be checked at other frequencies. Overall accuracy is ±0.5 dB to 500 MHz, ±1 dB to 1000 MHz, and ±2 dB to 1400 MHz. This error is contributed by the vernier alone and does not include the basic flatness error at maximum output.
STEP
The accuracy of the Step Attenuator can be measured by using a suitable attenuation test set or by directly substituting precision RF attenuator pads for each 10 dB step of the Attenuator. The difference between the two outputs represents the Attenuator error. An RF detector can be used to recover the signal at levels down to approximately -40 dBm. Below this level, an RF amplifier or sensitive receiver (spectrum analyzer) must be used. Allowable error is ±0.5 dB to 500 MHz, ±1 dB to 1000 MHz, and ±2 dB to 1400 MHz. This error is that produced by the Step Attenuator alone and does not include the basic flatness or vernier error
5.3.12 SWEEP TIME (HORIZONTAL OUTPUT) CHECK
Connect the horizontal output of the sweep generator to the oscilloscope vertical input. Adjust the oscilloscope controls for an automatic, internally generated and triggered sweep of 2 msec/division and a vertical sensitivity of 2 V/division. Set the sweep generator SWEEP TIME selector to LINE and ensure that the PULL TRIG switch is pushed in. Adjust the oscilloscope vertical position, horizontal position, and trigger level to obtain the waveform shown in Fiaure 5-6.
Set the sweep generator SWEEP TIME selector to .1-.01 SEC. Ensure that the VAR/MANUAL control is fully clockwise. The wait time should disappear and the sweep time should be less than 10 msec with approximately equal sweep and retrace time periods. Adjust the oscilloscope time base to 50 msec/division. Adjust the sweep generator VAR/MANUAL control fully counterclockwise. The sweep time should be more than 100 msec with a retrace time of approximately 0.01 sec.
NOTE
The retrace time period remains constant within any one SWEEP TIME range setting, and the VAR/MANUAL control varies the sweep time period. With the VAR/MANUAL control fully clockwise, the sweep and retrace times are approximately equal. With the VAR/MANUAL control fully counterclockwise, the sweep time becomes approximately 10 times the retrace time.
Repeat these checks for the 1-.1, 10-1, and 100-10 SEC positions of the SWEEP TIME selector switch. Adjust the oscilloscope time base as necessary to ensure that the VAR/MANUAL control will adjust the sweep time from longer than the maximum to shorter than the minimum specifications for each range.
Set the SWEEP TIME selector to MANUAL and adjust the VAR/MANUAL control throughout its range. A DC voltage should be present that is variable from -8 V ±0.5 V with the control fully clockwise.
Set the SWEEP TIME selector to the .1-.01 SEC position and pull out the PULL TRIG switch. The sweep should now be disabled. Each depression of the front-panel TRIG switch should produce one complete sweep cycle.
NOTE
The triggered mode of operation is possible only in the variable rate positions, and will not operate in the LINE position of the SWEEP TIME selector.
5.3.13 MARKER SYSTEM CHECK
Connect the equipment as in Section 5.3.1. The following check is for a harmonic marker. Specifications, with the exception of spurious markers, are the same for either single frequency or harmonic type markers, and the procedure for verification of performance is the same for both types.
Single frequency markers should have no spurious markers throughout the swept range. Harmonic type markers may or may not have small spurious markers at one half or one third the specified marker interval.
MARKER SIZE
Observe the markers and ensure they are of equal amplitude throughout the range.
Sat the estillescope vertical gain to 2 V/division and adjust the MARKER SIZE control fully clockwise. The markers chould be approximately 1 Vap in amplitude. Adjust the MARKER SIZE control fully counterclockwise and cot the oscilloscope vertical gain to 1 mV/division. The markers oscilloscope vertical gain to 1 mv/division. The markets sween generator's bottom cover and position the Plotter switch to its Plot position (This slide switch is located directly behind the front-panel DEMOD IN connector. Normal position is with slide lever toward center of instrument the Plot position is with slide lever toward the right side papel ) Positive restified markers should be present for use with X X recording instruments. The amplitude will be dependent on the sutput impedance of the BE detector being used. The amplitude should be adjustable from approximately 6 V maximum to 1 mV minimum with a detector impedance of 1 Mohm or from 0.5 V to 1 mV with a detector impedance of 0 obms
NOTE
The sweep width must be decreased or the sweep time increased to observe the rectified marker. Return the Plotter switch to its normal position and replace the instrument's bottom cover.
MARKER TILT
Pull the PULL TILT switch out and set the MARKER SIZE control to minimum. A horizontal marker will be present having a fixed amplitude of approximately 10% of the total horizontal deflection. Increasing the MARKER SIZE control clockwise will add the normal vertical marker to the horizontal marker, causing the marker to tilt toward a vertical position.
MARKER WIDTH
Push the PULL TILT switch back in. Turn on the 1 MHz markers and adjust the MARKER SIZE control for approximately a 4 division peak-to-peak marker. Set the MARKER WIDTH selector to its widest position. Adjust the FREQUENCY and SWEEP WIDTH controls to calibrate the oscilloscope for a 1 MHz sweep width.
Adjust the FREQUENCY control to center the birdy zero beat on the oscilloscope center graticule line and note that the marker width is approximately 400 kHz (each division equals 100 kHz). Decrease the MARKER WIDTH switch one position and note that the marker width is approximately 200 kHz. Decrease the MARKER WIDTH switch one position and note that the marker width is approximately 100 kHz. Decrease the MARKER WIDTH switch to the most narrow position. Note that the marker width is now approximately 15 kHz.
Figure 5-8. M2J Controls
Figure 5-9. Sweep Rate Controls
MARKER ACCURACY
MARKER ACCURACI Marker accuracy may be verified by one of several methods. The first method requires a signal generator and frequency counter covering the desired marker frequency. First adjust the sweep generator's center frequency to the marker's frequency and the sweep width to approximately 2 MHz. Connect the output from the signal generator to the rearpanel MARKER IN connector, and carefully adjust the signal generator for a zero beat with the internally generated birdy marker. Next, connect the signal generator's output to the counter and read the signal generator frequency which is now identical to the marker's frequency.
The second method uses the counter only, but requires the removal of the instrument and marker module covers. Probe the marker box with the input lead from the counter until sufficient signal is picked up to provide a counter reading. The highest crystal frequency used is approximately 50 MHz. Markers above this frequency use harmonics of the crystal frequency. The allowable error is 0.005% of the crystal frequency.
Test equipment for the marker accuracy check is not listed in the recommended test equipment table, since the requirements vary with the method and the specific markers installed. Also, the inherent stability of the quartz crystal makes a marker accuracy check unnecessary in all but the most critical applications.
5.3.14 EXTERNAL PROGRAMMING
External programming inputs are not normally checked during incoming inspection unless these special functions are to be used in a particular application. The external programming circuits are covered in Section 3 under Operating Instructions. If it is necessary to check these functions at incoming inspection, reference can be made to that section for complete set-up instructions.
5.4 CALIBRATION PROCEDURE
Remove the instrument top cover, bottom cover, left side panel, and M1H and M2J module covers. Allow a 15 minute warm-up period before calibrating. In general, calibration must be performed in the sequence given.
5.4.1 +18 V ADJUSTMENT
Connect the digital voltmeter to the +18 V supply, pin 6 on the power plug, and adjust resistor R9 to produce +18 V ±10 mV. (See Figure 5-7.)
5.4.2 -18 V CHECK
Connect the digital voltmeter to the -18 V supply, pin 4 on the power plug. The reading must be -18 V ±50 mV.
5.4.3 -20 V CHECK
Connect the digital voltmeter to the -20 V supply, pin 5 on the power plug. The reading must be -20 V ±0.3 V.
5.4.4 -16 V CHECK
CAUTION
The ±16 V supplies are not short circuit protected.
Connect the digital voltmeter to the -16 V supply, pin 3 of the REMOTE jack. It must read -16 V ±0.1 V. (Record reading.)
5.4.5 +16 V ADJUSTMENT
Connect the digital voltmeter to the +16 V supply, pin 2 of the REMOTE jack. Adjust R55 (see Figure 5-8) to obtain exactly the same voltage, but of opposite polarity, as was recorded for the -16 V supply in Section 5.4.4.
5.4.6 SWEEP RATE ADJUSTMENTS – MODULE M1H
Set the front-panel controls as shown in Figure 5-9. Connect the scope vertical input to the ouput of the rate generator, pin 10 of the REMOTE jack, and adjust the scope vertical and horizontal time base controls to produce a stable pattern similar to Figure 5-10. Adjust the M1H Cent control to obtain an output symetrical about zero volts, and the M1H Size control to obtain the 32 Vpp amplitude.
These adjustments should be made as precisely as possible. The ±16 V references available at pins 2 and 3 of the REMOTE jack can be used to check the accuracy of the vertical calibration of the oscilloscope.
Set the front-panel VAR/MANUAL control fully counterclockwise and adjust the M1H Int Bal to produce a sweep time of 0.12 seconds. (See Figure 5-11.)
Set the front-panel SWEEP TIME selector to LINE and adjust the M1H Clamp control to clamp the negative going peak of the M1H output to -16 V. (See Figure 5-12.)
Adjust the Wait control, mounted on top of the SWEEP TIME switch assembly (see Figure 5-9), until the wait time as shown in Figure 5-12 is approximately 1 msec.
5.4.7 SWEEP DRIVE ADJUSTMENTS - MODULE M2J
Connect the scope vertical input to test point 1 in the M2J module (see Figure 5-8). Set the front-panel FREQUENCY control to produce 0 V at pin 6 of the module. The center frequency dial must read 250 MHz on the 0 to 500 MHz scale. If not, loosen the set screw holding the FRE-
Figure 5-11. M1H Int Bal Adjustment
Figure 5-12. Sweep Ramp
Figure 5-13. Lin Ref Adjustment
QUENCY dial to its shaft and reposition. Next, set the FREQUENCY vernier to produce -8 V at pin 8 of the module. The indicator line on the FREQUENCY vernier must be pointing toward the frequency indicator. If not, loosen the set screw and reposition. Next, set the frontpanel SWEEP WIDTH control completely counterclockwise (CW position) and adjust resistor R4 to produce 0 V at test point 1. Set the front-panel SWEEP WIDTH control completely clockwise and the SWEEP WIDTH range switch in the 500 MHz position, and adjust resistor R13 to produce a 28 Vpp signal at test point 1.
Without disturbing the front-panel FREQUENCY or SWEEP WIDTH controls, return the scope to an X-Y operating mode with the horizontal output of the sweep generator driving the scope horizontal input. Set the SWEEP TIME selector to .1-01 SEC and adjust the scope display width to 11 divisions (0.5 divisions overlap on each end) (See Figure 5-13a.)
Connect the scope vertical input to M2J test point 2, which is the top side of any of the three diodes adjacent to Q4. (Linearity correcting resistors may or may not be connected to the diodes, depending on the inherent linearity of the sweep oscillator.) Adjust resistor R16 to position the "knee" as shown in Figure 5-13b. The M2J cover and the instrument left side panel may now be replaced.
5.4.8 LEVEL MIN AND MAX ADJUSTMENTS – MODULE M10H
Adjust the instrument controls as follows:
| BAND | 0 - 500 |
|---|---|
| FREQUENCY | 300 MHz |
| SWEEP WIDTH | full ccw (CW) |
| OUTPUT | +10 dBm |
Set the power meter to its +10 dBm range and connect its sensor to the RF OUT connector.
Adjust the M10H Level Max control to produce a power meter reading of +10 dBm. Turn the OUTPUT vernier control completely counterclockwise to indicate -20 dBm. Set the power meter to its -20 dBm range and adjust the M10H Level Min control to produce a power meter reading of -20 dBm.
5.4.9 CENTER FREQUENCY ADJUSTMENT – MODULES M9H & M19H
Connect the equipment as in Section 5.3.1. Locate the harmonic marker corresponding to 250 MHz (count up from the zero lock-in point). Adjust the M9H Cent Band 1 control to position this marker to the exact center of the display. Gradually reduce the front-panel SWEEP WIDTH control to minimum while readjusting the M9H control to maintain the marker centered on the display.
Change the BAND switch to 450 - 950. Return the SWEEP WIDTH control to maximum. Locate the 50 MHz harmonic marker that corresponds to a frequency of 700 MHz. (Use a CW signal generator and the external marker circuit to identify the proper 50 MHz harmonic marker.) Adjust the M19H Cent Band 2 control to position the 700 MHz marker to the exact center of the display. Gradually reduce the front-panel SWEEP WIDTH control to minimum while readjusting the M19H control to maintain the marker centered on the display.
Change the BAND switch to 900 - 1400. Return the SWEEP WIDTH control to maximum. Locate the 50 MHz harmonic marker that corresponds to a frequency of 1150 MHz. (Use a CW signal generator and the external marker circuit to identify the proper 50 MHz harmonic marker.) Adjust the M19H Cent Band 3 control to position the 1150 MHz marker to the exact center of the display. Gradually reduce the front-panel SWEEP WIDTH control to minimum while readjusting the M19H control to maintain the marker centered on the display.
5.4.10 SWEEP WIDTH ADJUSTMENT - MODULE M2J
With the instrument operating as set-up in Section 5.4.9, set the FREQUENCY control for 0 MHz. (Make sure the FREQUENCY vernier is not disturbed.) Set the front-panel SWEEP WIDTH control to its full clockwise position and adjust the M2J Sweep Width 1 control to position the zero lock-in point to the center of the display. Reduce the front-panel SWEEP WIDTH control to minimum while readjusting the M2J control to maintain the zero lock-in point control to maintain the zero lock-in point control to maintain the zero lock-in point centered on the display.
Change the BAND switch to 450 - 950. Do not disturb the FREQUENCY control. Return the front-panel SWEEP WIDTH control to maximum and locate the 50 MHz harmonic marker corresponding to 450 MHz. (Use an external CW signal generator and the external marker circuit to identify the proper 50 MHz harmonic marker.) Adjust the M2J Sweep Width 2 control to position the 450 MHz marker to the center of the display. Reduce the frontpanel SWEEP WIDTH control to minimum while readjusting the M2J control to maintain the 450 MHz marker centered on the display.
Change the BAND switch to 900 - 1400. Do not disturb the FREQUENCY control. Return the front-panel SWEEP WIDTH control to maximum and locate the 50 MHz harmonic marker corresponding to 900 MHz. (Use an external CW signal generator and the external marker circuit to identify the proper 50 MHz harmonic marker.) Adjust the M2J control to maintain the 900 MHz marker centered on the display.
5.4.11 SWEEP SAMPLE ADJUSTMENT - MODULEM5H
Connect the RF detector to the M5H Sweep Sample Out-5-11
put jack (J4) using the adapter cable supplied in Service Kit K102 (or fabricate the equivalent SMC to BNC adapter cable), and adjust the Sweep Sample Adj. to produce a detected output of approximately 35 mV.
5.4.12 MARKER SIZE ADJUSTMENT - MODULE M6
Each marker module has a Size control which is accessible from the under side of the sweep generator when the bottom cover is removed (see Figure 5-2). The control is adjusted until a saturated marker is obtained on the scope display when operating the instrument as shown in Figure 5-4. A saturated marker is obtained when a further increase in the marker module's Size adjustment does not increase the marker amplitude on the scope display. Increasing the Size adjustment beyond this point will result in spurious markers on the display.
5.5 TROUBLESHOOTING
Effective troubleshooting requires a thorough understanding of the block diagram and circuit descriptions located in Section 4 of this manual. The performance test and calibration procedures will aid in localizing the trouble symptom to a particular module or PC board. Once this has been accomplished, the module or board can be replaced or repaired with the aid of the proper schematic and parts layout diagram. In general, it is preferable to replace a defective module or PC board assembly.
Equipment troubles are frequently due simply to improper control settings; therefore, before engaging in a troubleshooting procedure, be sure front-panel controls are set in proper operating position. Refer to Section 3 of this manual for complete explanation of each control's function along with typical operating instructions.
After verifying that the trouble is not improper setting of the controls or test set-up, make a thorough visual inspection of the instrument for such obvious defects as loose or missing screws, broken wires, defective module-pin sockets, loose RF cables, and burned or broken components.
After localizing the problem, voltage and resistance checks will help find the defective component.
For troubleshooting purposes, it is permissible to operate the Model 2000 with any of the plug-in modules or RF cables removed; however, the instrument should be turned off when removing or installing modules. If substitute modules are available, possibly from another Model 2000, this provides an easy method of verifying if a suspected module is defective.
RF cables can be disconnected from the module output connectors, and a power meter or spectrum analyzer can be connected directly to the module connector for power
level or frequency measurements. (The SMC to BNC adapter cable in Service Kit K102 is designed for this purpose )
A problem in a power supply may cause many symptoms pointing to other areas, and should be checked when the symptom does not indicate a specific problem. The ±18 V and -20 V supplies are located on the rear chassis printed circuit board, and the ±16 V reference voltage supplies are located in the M2J module. Performance of these supplies is indicated in the calibration procedure.
5.5.1 TROUBLESHOOTING HINTS
Following is a list of several typical symptoms, accompanied by the possible cause(s) or a troubleshooting procedure. It is assumed the instrument has been properly calibrated previously, and that a warmup period will precede troubleshooting.
INTERMITTENT OPERATION
Check for loose RF cables or loose modules. If none, check for defective module pin sockets.
±18 V OUT OF CALIBRATION
If the +18 V supply measures over +25 V, change the regulator, IC1. If the ±18 V supplies measure low, disconnect the Power Supply jack and carefully check for ±18 V at plug P2. If the ±18 V supplies are now correct, low voltage was due to over-current limiting by the Power Supply. Unplug modules until the overload is found.
NO RF SWEEP
First check pin 12 of the M1H module for the presence of a 32 Vpp ramp. This ramp indicates proper operation of the M1H. Next, check for the ramp at the input of the M2J pin 7. Finally, check the output of the M2J at pin 9. It should be similar to the input except it will be lower in amplitude, approximately 12 Vpp, and will have an average value of 0 V when the front-panel FREQUENCY control is set to midband. If the M2J output is correct, the trouble is probably in the M9H or M19H Sweep Oscillator module.
NO RF OUTPUT
All bands - Defective Attenuator or RF cables connecting to the input or output of the Attenuator. Single band only -If only one band does not work, check for the switched B-1, B-2, and B-3 voltages at modules M9H, M10H, and M19H as shown on the instrument Wiring Diagram.
RF OUTPUT NOT FLAT
The most common cause is the external RF detector being defective. Another is the monitor diode located in the M19H module. This is a point contact diode, and can be damaged if the RF output is momentarily connected to a B+ voltage. A good monitor diode will produce a negative detected voltage (pin 8 of M19H) approximately twice the
amplitude of the external detector. For example, at an RF output of +10 dBm, an external RF detector will read approximately .8 V. The internal monitor will read approximately -1.6 V.
FREQUENCY UNSTABLE (JITTER)
Check all modules for loss hold-down screws, especially module M2J. Check the ±16 V reference supplies. Operating the instrument in a strong magnetic field, such as sitting on top of, or adjacent to, another instrument containing a large power transformer can produce 60 Hz hum modulation.
If all bands are unstable, check for excessive ripple on the nower supplies
SWEEP BATE PROBLEM
The probable cause is a defective M1H module or wiring to the front-panel SWEEP TIME selector. See the calibration procedure for verifying proper operation.
MARKER PROBLEMS
To isolate the cause of a marker problem when the symptom does not clearly indicate a specific circuit or component first check the sweep sample output at the M5H
Sweep Sample Output connector. It should be a detected signal of between 30 and 50 mV. If the proper sweep sample signal is not present, it indicates that the trouble is in the M5H, the Sweep Oscillator module (check all bands) or connecting sweep sample cables
Next connect the detector in place of the terminating plug P102 A signal at this point indicates all jumper cables and RE jacks on the M6 modules are intact. Then check for the hirdy output at nin 3 of the marker module. A 10 to 15 mVnn hirdy is sufficient to drive the M5H module, and indicates the M6 module is operating properly. With the 10 m/np birdy present at the input of the MEU (size 1.2) 3, and 4), a 32 Vpp signal will be produced at the output (pin 7) This indicates prepay appretion of the MELL This output signal at pin 7 is controllable in width by the frontpanel MARKER WIDTH control. The signal is now routed through the front-panel MARKER SIZE control to the rear-panel SCOPE VEBT connector A 1 Vpp signal is normally at this point when the front-papel MARKER SIZE control is set to maximum A common marker problem occurs when one of the interconnecting cables between the M6 modules is loose. This causes a notch in the sweep sample input to the module causing uneven
Figure 5-14. Top View
MIOH MI R 36 15K 10K 2. R 40 470K 220K 10C R 42 680K NONE NO R 43 2.7K 2.7K 11 R 49 NONE 1.2M 11
M10H/M10H-1/M10H-2 OUTPUT AMPLIFIER
CRI. 10. 11. 21 : 1N4004 CR2~5 15~16 : BB205
CRI, 2 = INSZAG (GI)
M6H-1 HARMONIC MARKER (] MHZ)
M6S SINGLE FREQ. MARKER
MANUAL CHANGES - MODEL 2000
WAVETEK's product improvement program incorporates the latest electronic developments into these instruments as rapidly as development and testing permit. Due to the time required to document and print these instruction manuals, it is not always possible to include the change information in the current printing. The following changes should be made to this manual:
- MIOH 08 is now a selected 2N5458 FET, Wavetek P/N 4999-00-0001.
- M19H R4* is now 150 ohms, Wavetek P/N 4700-15-1500. R32* is now 2.2 kohms, Wavetek P/N 4700-15-2201. Q3 is now a 2N5462 FET, Wavetek P/N 4901-05-4620.
- M6H-50 Q1 is now a 2N3904 transistor, Wavetek P/N 4901-03-9040. Q2 is an A430 transistor, Wavetek P/N 4902-00-4300. Q3 is a 2N5458 FET, Wavetek P/N 4901-05-4580. 04 is a 2N5088 transistor, Wavetek P/N 4901-05-0880.
- M9H CR8, CR9 are now H-P 5082-2835, Wavetek P/N 4809-02-0002.
- M19H Delete CR11, CR12, C19, Q13, R39, R40, R41, and change Q14 to APX, BFR90, Wavetek P/N 4902-00-0940. Change Q3 to MOT, 2N5462, Wavetek P/N 4901-05-4620. Change R4* and R32* to 150 ohm and 2.2 kohm, Wavetek P/N 4700-15-1500 and 4700-15-2201, respectively.
MECH Item 27 P/N is 2810-10-0003.
M5G/M5H/M5H-I/M5H-2 SWEEP SAMPLE OUTFUT DEV E EXTERN R9 5 PARTS IN C23 R43 2 08 BIRDY NPUT л __ SIZE DINOTE: FOR M5H-2 OMIT CIB. FOR ALL OTHERS, OMIT J5 TO SUAPER
The Marker Adder module in this instrument has been redesigned. It is now built on a PC board instead of a metal chassis, and some discrete components have been replaced by integrated circuits. All instrument specifications and operating procedures are unchanged.
Loading...