TTI TG550 Service Manual
TG550
5 MHz Precision
Function Generator
Service Manual
Book Part Number 48591-0610 - Issue 1
Table of Contents
Specification 3
Safety 6
EMC 7
Installation 8
General 9
Functional Description 11
Circuit Descriptions 12
Calibration 14
Parts List 17
Component Layouts 24
Circuit Diagram 25
2
Specification
Specifications apply at 18º - 28º after one hour warm-up, at maximum output into 50Ω.
FREQUENCY
Frequency Range: 0·005Hz to 5MHz in 7 overlapping decade ranges with adjustment by
coarse and fine verniers.
Vernier Range: 1000:1 on each range.
Frequency Display: Auto-ranging reciprocal measurement giving 4-digit resolution down to
10Hz (to 1Hz on the 5Hz range); resolution is fixed at 0·01Hz below 10Hz
(0·001Hz below 1Hz on the 5Hz range).
Accuracy is ± 1 digit to 2·1Hz (to 0·21Hz, Symmetry off, or to 0·42Hz,
Symmetry on, on the 5Hz range); below this the accuracy is ± 1% of range
full scale (unspecified with Symmetry on).
Frequency Locking: With vernier setting between 10% and 100% of range maximum, frequency
can be locked to the crystal reference to maintain it at the displayed value ±
0·01%.
WAVEFORMS
Waveform specifications apply for the top decade of each frequency range.
SINE
Distortion: Less than 0·5% on 500Hz, 5kHz and 50kHz ranges; less than 1% on 5Hz,
50Hz and 500kHz ranges; all harmonics >25dB below fundamental on
5MHz range.
Amplitude Flatness: ± 0·2dB to 200kHz; ± 2dB to 5MHz.
TRIANGLE
Linearity:
Better than 99% to 200kHz.
SQUAREWAVE
Rise and Fall Times: <45ns.
Mark-Space Ratio: 1:1 ± 1% to 100kHz.
DC
Range: ± 10V (unterminated).
SYMMETRY
Symmetry Range: Variable typically between 1:9 and 9:1 (on top decade of each range),
frequency divided by 10 when Symmetry is selected.
MODULATION MODES
Modulation can be used with all waveforms and at any frequency.
Sweep
Sweep Mode: Internal: linear or logarithmic; sweep Start and Stop frequencies
displayed at a press of a button.
External: linear.
Sweep Width: Up to 1000:1 within each range.
Sweep Rate: Internal sweep rate adjustable from typically 20ms to 20s.
External Sweep: By signal applied by SWEEP IN/OUT socket.
3
Amplitude Modulation
Modulation Depth: Variable 0 to 100% typical.
Modulation Frequency: 400Hz internal. DC to 100kHz external.
External Modulation: By signal applied to COUNT/AM IN socket.
OUTPUTS
50Ω Main Out
Output Impedance:
50Ω.
Amplitude:
2mV to 20V peak-peak open circuit (1mV to 10V peak-peak into 50Ω) in
four switch-selectable ranges with 20dB vernier control within each
range.
Attenuator: 0, –20, – 40 or – 60dB.
DC Offset Range:
±10V. DC offset plus signal peak limited to ±10V (±5V into 50Ω); CLIP
shows in display when offset + signal peak exceeds ±10V. DC offset plus
waveform attenuated proportionally by the attenuator.
600Ω Main Out
Alternative output socket providing the same signal as the 50Ω Main Out but from 600Ω. The 50Ω
and 600Ω sockets are not independent.
Aux Out
Output Characteristics: Frequency, symmetry and phase the same as main outputs.
Output Level: 0 to 5V TTL/CMOS logic levels capable of driving 2 standard TTL loads.
Sweep Out
When internal sweep is selected the sweep signal is available as a 0 to 3V ramp from 600Ω.
INPUTS
Sweep In
The SWEEP IN/OUT socket is set to Sweep In when EXT SWEEP is selected.
Input Impedance:
10kΩ.
Input Sensitivity: 0 to 3V for 1000:1 sweep.
Maximum Allowable
Input Voltage:
± 10V.
Sweep Linearity: Better than 1%
Maximum Slew Rate of
Sweep Voltage:
0·1V/µs.
AM In
The AM/COUNT IN socket is set to AM input when EXT AM is selected.
Input Impedance:
40kΩ.
Input Sensitivity: Approximately 2V peak-peak for 50% modulation.
Maximum Allowable
Input Voltage:
± 10V.
4
Count In
The AM/COUNT IN socket is set to external frequency measurement when EXT COUNT is
selected.
Input Impedance:
1MΩ//25pF.
Input Sensitivity: 50mVrms (sinewave).
Maximum Allowable Input
Voltage:
50Vdc/50Vrms to 400Hz with respect to ground
, reducing to
1Vrms above 1MHz.
DISPLAY FUNCTIONS
The LCD shows generator frequency simultaneously with output amplitude/offset, together with
various status annunciators. Alternatively, it is the external frequency measurement display.
Internal Measurement Accuracy
Frequency: Auto-ranging reciprocal measurement giving 4-digit resolution down to
10Hz (to 1Hz on the 5Hz range); resolution is fixed at 0·01Hz below
10Hz (0·001Hz below 1Hz on the 5Hz range).
Accuracy is ± 1 digit to 2·1Hz (to 0·21Hz, Symmetry off, or to 0·42Hz,
Symmetry on, on the 5Hz range); below this the accuracy is ± 1% of
range full scale (unspecified with Symmetry on).
Amplitude: Display shows peak-to-peak amplitude or rms value. Display corrected
for attenuator setting. 3-digit resolution, accuracy typically ±5% of
range full scale.
DC Offset: 3-digit resolution; accuracy typically ±2% setting ± 1 digit.
Display corrected for attenuator setting.
External Frequency Measurement
Frequency Range: 5Hz to 20MHz, fully autoranging.
Input Sensitivity: 50mVrms (sinewave).
Measurement Time: Selectable 0·5s or 5s.
Resolution: 6 digits in 0·5s; 7 digits in 5s.
Accuracy: ± 1 digit ± timebase accuracy.
Timebase Accuracy: ± 10ppm initial error; ±5 ppm/year ageing rate; typically less than
0·5 ppm/ºC.
GENERAL
POWER REQUIREMENTS
AC Input Voltage: 230V or 115V nominal, 50/60Hz, by internal adjustment; operating range
± 14% of nominal. Installation Category II.
Power Consumption: 25VA max.
Operating Range: +5°C to +40°C, 20% to 80% RH.
Storage Range: -10°C to +65°C
Environmental: Indoor use at altitudes up to 2000m, Pollution Degree 1.
Size: 260 (W) x 88 (H) x 235 (D) mm (10.2 x 3.4 x 9.2") excluding handle and
feet.
Weight: 1.9kg (4.2lb).
Safety: Complies with EN61010-1.
EMC: Complies with EN50081-1 and EN50082-1.
5
Safety
This instrument is Safety Class I according to IEC classification and has been designed to meet
the requirements of EN61010-1 (Safety Requirements for Electrical Equipment for Measurement,
Control and Laboratory Use). It is an Installation Category II instrument intended for operation
from a normal single phase supply.
This instrument has been tested in accordance with EN61010-1 and has been supplied in a safe
condition. This instruction manual contains some information and warnings which have to be
followed by the user to ensure safe operation and to retain the instrument in a safe condition.
This instrument has been designed for indoor use in a Pollution Degree 1 environment (no
pollution, or only dry non-conductive pollution) in the temperature range 5°C to 40°C, 20% –80%
RH (non-condensing). It may occasionally be subjected to temperatures between +5° and –10°C
without degradation of its safety.
Use of this instrument in a manner not specified by these instructions may impair the safety
protection provided. Do not operate the instrument outside its rated supply voltages or
environmental range. In particular excessive moisture may impair safety.
WARNING! THIS INSTRUMENT MUST BE EARTHED
Any interruption of the mains earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited. The protective action must not be
negated by the use of an extension cord without a protective conductor.
When the instrument is connected to its supply, terminals may be live and opening the covers or
removal of parts (except those to which access can be gained by hand) is likely to expose live
parts. The apparatus shall be disconnected from all voltage sources before it is opened for any
adjustment, replacement, maintenance or repair.
Any adjustment, maintenance and repair of the opened instrument under voltage shall be avoided
as far as possible and, if inevitable, shall be carried out only by a skilled person who is aware of
the hazard involved.
If the instrument is clearly defective, has been subject to mechanical damage, excessive moisture
or chemical corrosion the safety protection may be impaired and the apparatus should be
withdrawn from use and returned for checking and repair.
Make sure that only fuses with the required rated current and of the specified type are used for
replacement. The use of makeshift fuses and the short-circuiting of fuse holders is prohibited.
Do not wet the instrument when cleaning it.
The following symbols are used on the instrument and in this manual:-
Caution - refer to the accompanying documentation, incorrect
operation may damage the instrument.
terminal connected to chassis ground.
alternating current.
6
EMC
This generator has been designed to meet the requirements of the EMC Directive 89/336/EEC.
Compliance was demonstrated by meeting the test limits of the following standards:
Emissions
EN50081-1 (1992) Generic emission standard for residential commercial and light
industry. Test methods and limits used were:
a) EN55022 Conducted, Class B
b) EN55022 Radiated, Class B
Immunity
EN50082-1 (1992) Generic immunity standard for residential, commercial and light
industry. Test methods and limits used were:
a) EN60801-2 (1993) Electrostatic Discharge, 8 kV air discharge.
b) IEC801-3 (1984) RF Field, 3 V/m.
c) IEC801-4 (1988) Fast Transient, 1 kV peak (AC line), 0·5kV peak (signal lines).
Cautions
To ensure continued compliance with the EMC directive the following precautions should be
observed:
a) connect the generator to other equipment using only high quality, double-screened cables.
b) after opening the case for any reason ensure that all signal and ground connections are
remade correctly before replacing the cover. Always ensure all case screws are correctly
refitted and tightened.
c) In the event of part replacement becoming necessary, only use components of an identical
type, see Parts List.
7
Installation
Mains Operating Voltage
The operating voltage of the instrument is shown on the rear panel. Should it be necessary to
change the operating voltage from 230V to 115V or vice-versa, proceed as follows:
1. Disconnect the instrument from all voltage sources.
2. Remove the 4 screws which hold the upper and lower case halves together and lift off the
case lower.
3. Remove the 6 screws securing the main pcb to the case upper and lift the pcb free,
complete with front and rear panels.
4. Change the appropriate zero-ohm links beside the transformer on the pcb:
Link LK2 only for 230V operation
Link LK1 and LK3 only for 115V operation
5. Refit the pcb to the case upper, ensuring all connections (especially safety earth) are
remade as before, and refit the case lower.
6. To comply with safety standard requirements the operating voltage marked on the rear
panel must be changed to clearly show the new voltage setting.
7. Change the fuse to suit the new operating voltage, see below.
Fuse
The correct time-lag fuse must be fitted for the selected operating voltage.
For 230V operation use 125mA (T) 250V HBC.
For 115V operation use 250mA (T) 250V HBC.
Make sure that only fuses with the required rated current and of the specified type are used for
replacement. The use of makeshift fuses and the short-circuiting of fuse holders are prohibited.
Mains Lead
When a three core mains lead with bare ends is provided it should be connected as follows:
Brown - Mains live
Blue - Mains Neutral
Green/Yellow - Earth
WARNING! THIS INSTRUMENT MUST BE EARTHED
Any interruption of the mains earth conductor inside or outside the instrument will make the
instrument dangerous. Intentional interruption is prohibited.
8
General
Service Handling Precautions
Service work or calibration should only be carried out by skilled engineers. Please note the
following points before commencing work.
The tracks on the printed circuit board are very find and may lift if subjected to excessive heat.
Use only a miniature temperature controlled soldering iron and remove all solder (on both sides of
the joint) with solder wick or suction before attempting to remove a components.
Many of the integrated circuits are CMOS devices and are should be taken when handling to
avoid damage by static discharge.
Dismantling the instrument
1. Invert the instrument and remove the 4 screws next to the rubber feet.
2. Lift off the case lower ensuring the front and rear panels stay with the case upper.
3. Remove the 6 screws securing the main pcb to the case upper and lift the pcb free,
complete with front and rear panels.
4. To remove the control pcb from the front panel, first pull off the small knobs and unplug
the two flat cable assemblies. Then desolder all other wire connections between main and
control pcbs (at the control board end), lift the assembly clear and undo the 8 screws
which hold the control board to the front panel; the control board can then be removed.
5. To gain access to the microcontroller the LCD must be removed.
6. The rear panel can be removed by undoing the tamper-proof safety earth connection.
7. Reassemble in the reverse order taking care to remake connections exactly as before,
particularly the safety earth wiring.
9
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