TG MHz Function Generator Service Manual

Transcription

1 TG MHz Function Generator Service Manual Book Part Number Issue 1

2 Table of Contents Specification 1 Safety 3 Installation 4 General 5 Circuit Descriptions 6 Calibration 7 Parts List 8 Component Layout 12 Circuit Diagram 13 FREQUENCY Frequency Range: Vernier Range: Vernier Accuracy: SWEEP MODE (EXTERNAL) Specification 0 2Hz to 20MHz in 8 overlapping decade ranges with fine adjustment by a vernier. >10:1 on each range. Typically ± 5% of full scale. Sweep Range: Typically >20:1. Input Impedance: Input Sensitivity: Maximum Allowable Input Voltage: Maximum Slew Rate of sweep voltage: 82 kω Typically 0 to 2V for 10:1 sweep. ± 10V 0 1V/us OPERATING MODES (Specifications apply for the top decade of each frequency range and output 10V peak-to-peak into 50Ω termination). SINE Distortion: Amplitude Flatness: Typically 2% on 200, 2k and 20k ranges. ± 0 2dB to 200kHz; ± 2dB to 20MHz. TRIANGLE Linearity: Typically 99% on khz ranges. 1

3 SQUAREWAVE Rise and Fall Times: <22ns DC Range: ±10V from 50 Ω SYMMETRY Symmetry Range: Typically variable from 1:6 to 6:1 up to 500kHz. OUTPUTS 50Ω Three switch-selectable ranges with 26dB vernier control within each attenuator range. 0dB Range: 1V to 20V peak-to peak from 50 Ω (0 5V to 10V into 50 Ω). -20dB Range: 100mV to 2V peak-to-peak (50mV to 1V into 50 Ω) -40dB Range: 10mV to 0 2V peak-to-peak (5mV to 0 1V into 50 Ω) DC Offset Control Range: TTL Capable of driving 4 standard TTL loads. GENERAL Power: Operating Range: Storage Range: ±10V from 50 Ω. DC offset plus signal peak limited to ±10V (±5V into 50 Ω). DC offset plus waveform attenuated proportionally in -20dB and -40dB position. 230V or 115V nominal 50/60Hz, adjustable internally; operating range ± 14% of nominal; 30VA max. Installation Category II. +5ºC to + 40ºC, 20% to 80% RH. -10ºC to +65ºC Environmental: Indoor use at altitudes up to 2000m, Pollution Degree 1. Electrical Safety: EMC: Size: Weight: Complies with EN Complies with EN55011 and EN (W) x 82(H) x 230(D) mm, (10 3 x 3 4 x 9 2 ) excluding feet. 1 5 Kg (3.3lb). 2

4 Safety This instrument is Safety Class I according to IEC classification and has been designed to meet the requirements of EN (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 EN 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. mains supply OFF. l mains supply ON. alternating current. 3

5 MAINS OPERATING VOLTAGE Installation The operating voltage of the instrument is shown on the rear panel. Should it be necessary to change the operating range from 230V to 115V or vice-versa, change the transformer connections following the appropriate diagram below: 230V Operating - Primaries in series 115V Operation - Primaries in parallel 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. 4

6 Service Handling Precautions Service work or calibration should only be carried out by skilled engineers. Please note the following points before commencing work. General The tracks on the printed circuit board are very fine 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 component. Care should be taken when handling to avoid damage by static discharge Dismantling the instrument 1. Invert the instrument and remove the 4 screws securing the case upper. Holding the case halves together, turn the instrument the correct way up and lift off the case upper ensuring the front and rear panels stay with the case lower. 2. To remove the pcb from the front panel, pull off the control knobs and remove the nuts beneath. Remove the 3 BNC nuts. 3. Reassemble in the reverse order. Caution EMC To ensure continued compliance with the EMC directive the following precautions should be observed: a) after dismantling the unit for any reason ensure that any signal and ground connections are remade correctly. Always ensure all screws are correctly refitted and tightened. b) In the event of part replacement becoming necessary, only use components of an identical type. 5

7 Power Supply - DC Regulation Circuit Descriptions The voltage regulators are mounted on a separate pcb. IC10 and IC11 provide ±15V, IC8 and IC9 provide ± 5V. Waveform Generation IC1 is an integrated waveform generator and provides sinewave, squarewave and triangle output. Q1 to Q6 select the range capacitor. The 20MHz and 2MHz ranges use the same range capacitor VC1. The dial and sweep voltages are summed by IC5A; IC5B inverts the output of IC5A. IC4C and IC4B select the full-scale input current to the frequency control pin 10 of IC1 for the different ranges as follows. On 2Hz to 200kHz ranges IC4B and IC4C select VR6 and R45. IC4D connects the FADJ pin to 0V. On 2MHz range IC4B and IC4C select VR9 and FADJ remains at 0V. On 20MHz range IC4B and IC4C select R44 (R52 is in circuit on all ranges). IC4D connects FADJ to 0V via R46; the 250uA current sink inside IC1 causes -3V to be developed across R46 setting IC1 to its frequency double mode. IC5C buffers the symmetry control. The control voltage to the DADJ pin needs to be inverted when sine or triangle are selected to maintain the same direction of operation of VR2 as in squarewave mode. IC5D provides the inversion. The waveform address pins A0 and A1 set the output waveform. The selected waveform is produced at the OUT pin and is 2Vpk-pk. Waveform Generation - Aux Output Preamplifier IC2 is a zero crossing detector with hysteresis provided by R19 and R59. R18,R17 and VR7 set the gain of IC3 to approximately 2 to give approximately 4Vpk-pk output. When no waveform is selected (DC), Q7 pulls pin 8 to 0V disabling the amplifier. The amplifier output is then in a high impedance state and IC7 input is grounded via IC3's feedback resistors. Output Amplifier R26,R27 and R54 set the gain to approximately 5 to give 20Vpk-pk output. D1,D2 D4 and D5 provide some protection against voltages being applied to the 50 Ω. IC6A amplifies the voltage set by VR4 the DC Offset control by 2.1 to give at least ±10V DC offset range. 6

8 Equipment Required Oscilloscope Distortion meter DMM Calibration Only the case upper needs to be removed to gain access to all adjustments. Holes through the pcb give access to the trimmers. Allow 30 minute warm-up before commencing. The 20MHz and 2MHz range calibrations are inter-active and therefore should be adjusted in the order shown. 1. Power Supply Check the power supply voltages at PJ2 on the PSU board 2. DC Offset +15V ± 0.5V -15V ± 0.5V +5V ± 0.25V -5V ± 0.25V Set Function switch to DC, set DC Offset control to centre detent, attenuators to 0dB. Adjust VR8 for 0V ± 10mV at Main Output 3. Frequency Select sinewave, connect a frequency counter to either output Set dial to MHz range adjust VC1 for 19.8 to 20.2MHz 2MHz range adjust VR9 for 1.98 to 2.02MHz 4. Amplitude 20kHz range adjust VR6 for 19.8 to 20.2kHz Select squarewave, dial at 2.0, 2k range, Amplitude control to maximum. Adjust VR7 for 10.2Vpk-pk into 50 Ω. 5. Distortion Set dial to 2.0, 2k range, sinewave, Symmetry switch to off. Adjust VR5 for minimum distortion. 7

9 Parts List PCB ASSY - MAIN - TG120 ( ) Part Number Description Position WASHER M3 IC10/11 HEATSINK WASHER M3 SPRING IC10/11 HEATSINK NUT M3 IC10 HEATSINK SCREW M3 X 10 IC10/11 HEATSINK BUSH POLYESTER TO220 IC WASHER (SIL-PAD) TO220 IC7 & IC10 HEATSINK CLIP GP02 FOR PCB MTG H/SINKS IC HEATSINK PCB MTG 50MM HIGH IC10/ HEATSINK PCB MTG 38MM PLAIN SWITCH SLIDE 2P2W SW3,4, SWITCH ROTARY 1P12W SW1 (STOP AT POSITION 8) SWITCH ROTARY 2P6W SW2 (STOP AT POSITION 4) FUSE 1.0AT SUBMIN PCB MTG FS1, HEADER3 WAY STRAIGHT.156P PJ BNC SKT PCB STR SQUARE BNC1,2, RES 10R0F W25 MF 50PPM R RES 10R2F W25 MF 50PPM R34, RES 36R0F W25 MF 50PPM R RES 47R0F W25 MF 50PPM R12,13,14,15,16,22, RES 180RF W25 MF 50PPM R RES 510RF W25 MF 50PPM R26, RES 560RF W25 MF 50PPM R RES 620RF W25 MF 50PPM R50, RES 820RF W25 MF 50PPM R RES 1K20F W25 MF 50PPM R RES 3K90F W25 MF 50PPM R RES 4K30F W25 MF 50PPM R RES 4K70F W25 MF 50PPM R1,19,20,58, RES 10K0F W25 MF 50PPM R9,25,42,43,55, RES 11K0F W25 MF 50PPM R24,47, RES 12K0F W25 MF 50PPM R RES 51K0F W25 MF 50PPM R RES 82K0F W25 MF 50PPM R RES 100KF W25 MF 50PPM R10,11,39,41,57 8

10 PCB ASSY - MAIN - TG120 ( ) continued.../ Part Number Description Position RES 2M00F W25 MF 50PPM R RES 41R2F W60 MF 50PPM MRS25 R32,33,35, RES 200RF W60 MF 50PPM MRS25 R28,29,30, RES NETWK SIL 100K X 8 RP POT 10K LIN SPLINE+DETENT 25MM VR2, POT 1K LIN SPLINE SHAFT 25MM VR POT 10K LIN LA20BU VR RES PS/H 220R CF 10MM VR RES PS/H 470R CF 10MM VR RES PS/H2K2 CF 10MM VR RES PS/H10K CF 10MM VR RES PS/H22K CF 10MM VR CAP10NZ 500V CER D10 P5 C CAP22PJ 100V CER NPO P2.5 C CAP10NZ63V CER HI K P5 C38, CAP 100PG 100V CER NPOP2.5 C35, CAP 22NJ 100V 5% P/E P5 C CAP47PJ 100V CER NPO P2.5 C21, CAP 150PJ 100V CER N150 P2.5 C CAP 10U 16V ELEC BIPOLAR P2 C CAP 10U 35V ELEC RE2 P2 C10,11,17,18,26,27,31, CAP 1000U 35V ELEC RE2 P5 C24, CAP 2U2 50V ELEC LOW LEAKAGE C CAP 22U 16V ELEC LOW LEAKAGE C CAP 100NK 63V P/E P5 C4,9,12-16,19,20,28,29,30,33, CAP 220NK 63V P/E P5 C CAP 2N2K 63V P/E P5 C TRIMCAP 2-22P P/P VC DIO 1N4148 D1, LED - T1 ROUND (3mm) - RED LED DIO ZEN 6V2 W5 D DIO ZEN 18V 1W3 D4, RECTIFIER BRIDGE W02G BR TRAN NPN BC549C Q IC NE529N IC IC LM324N IC5 9

11 PCB ASSY - MAIN - TG120 ( ) continued.../ Part Number Description Position IC NE5532N IC IC EL2099CT IC IC CLC430A IC IC MAX038CPP IC IC V/REG 7805 TO220 IC IC V/REG 7815 TO220 IC IC V/REG 7905 TO220 IC IC V/REG 7915 T0220 IC IC 74HC4053 IC PCB - MAIN WIRE SET CUT - PCB TG120 - CASED Part Number Description SLEEVE H30 X 20MML BLACK SWITCH WASHER M3 ZPST, AC RECEP (2), FRONT PANEL EARTH (1), SCREEN (6), P CLIP (1), P CLIP EARTH (1) WASHER M4, REAR PANEL EARTH (1), TRANSFORMER (2) WASHER M3 SHAKEPROOF AC RECEP WASHER M4 SHAKEPROOF TRANSFORMER SOLDER TAG SHAKEPROOF - 6BA FRONT PANEL EARTH SOLDER TAG SHAKEPROOF - 4BA REAR PANEL EARTH WASHER M3 SPRING, AC RECEP (2), PSU PCB/CASE (4), SCREEN (2), F/PNL EARTH (1) WASHER M4 SPRING, REAR PANEL EARTH (1), TRANSFORMER (2) SCREW N0.4 X 3/8 PSU PCB/CASE (4), P CLIP (1) SCREW N0.4 X 1/4 P CLIP EARTH NUT M3, AC RECEP (2), FRONT PANEL EARTH (1), SCREEN (4) NUT M4, REAR PANEL EARTH (1), TRANSFORMER (2) SCREW M3 X 70 CASING SCREW M3 X 10AC RECEP SCREW M4 X 10TRANSFORMER SCREW M3 X 12SCREEN SCREW M4 X 12 TAMPERPROOFREAR PANEL EARTH WASHER FIBRE M3PSU PCB/CASE CLAMP CABLE (P CLIP) 3.2MMD CABLE TIE 75 X 2.5MM SWITCH WIRES AC RECEPT 10

12 TG120 - UNCASED ( ) continued.../ Part Number Description KNOB 21MM DA GREY CAP C210 FOR 21MM KNOB GREY KNOB 11MM TP GREY CAP C110 FOR 11MM KNOB GREY SPACER RND 10MMID X 0.8MMT SW1, SPACER RND 10MMID X 3.5MMT VR FERRITE SLEEVE APPROX 7/14/15L TRANSFORMER SWITCH ROCKER DPST SOLDER LUGS SHROUD INSULATING (MS1 BOOT) AC RECEP MAINS LEAD 2M RA IEC SKT/STRRPEND AC MAINS RECEP 10AMP SKT3W AWG (Yellow) IDT ECLIPSE NEOPRENE PAD ECLIPSE TILT STAND FRONT PANEL OVERLAY FRONT PANEL REAR PANEL ECLIPSE CASE UPPER ECLIPSE CASE LOWER ECLIPSE CASE EXPANDER ECLIPSE FOOT TYPE A ECLIPSE FOOT TYPE B LABEL SER NO - THURLBY-THANDAR LABEL - CE WIRE SET CUT CHASSIS INSTRUCTION BOOK 11

13 12 Component Layout

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15 Circuit Diagram 13

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17 Thurlby Thandar Instruments Ltd Glebe Road, Huntingdon, Cambridgeshire PE29 7DR, England Telephone: (44) Fax: (44) e mail: sales@tti-test.com web site: