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TTI TG501 Service Manual

Function generator
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TG501
Function Generator
Service Manual
Book Part Number 48591-0130 - Issue 5

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Summary of Contents for TTI TG501

  • Page 1 TG501 Function Generator Service Manual Book Part Number 48591-0130 - Issue 5...

  • Page 2: Table Of Contents

    Table of Contents General Specification Functional Description Circuit Descriptions Calibration Parts List General Service Handling Precautions Service work should only be carried out by skilled engineers. Please note that 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 with solder wick or suction before to remove a omponent.

  • Page 3: Specification

    Specification (All specifications apply after warm-up in an ambient temperature range 18 o C-28 o C.) OPERATING RANGE Frequency Range: .005Hz to 5MHz in 7 overlapping decade ranges with fine adjustmentby calibrated vernier. Internal Mode Vernier Range: 1000:1 within each range. Vernier Accuracy: Better than ±5% of full scale.
  • Page 4 Power Requirements Input Voltage: 110/120V AC nominal 50/60Hz or 220/240V AC nominal 50/60Hz, adjustable internally. The TG501 will operate safely and meet specification within normal AC supply variations viz. 100-130V AC and 200-260V AC respectively. Power Consumption: 30VA Max. Environmental Operating Range: +5 o C to +40 o C, 20% to 80% RH.

  • Page 5: Functional Description

    Functional Description The relationships between the major circuit elements are shown in the block diagram opposite. The summing amplifier sums the voltages from the dial and from the sweep input, and its output controls the magnitude of the complementary current source and current sink. This current varies from approximately 5.2uA to 5.2mA for a 1000:1 frequency change (.005-5.0).
  • Page 6 This is the basic function generator loop in the Run mode and is shown by the double arrows in the block diagram. Triangle and squarewave are generated simultaneously as shown. The control logic determines Trig, Gate or Run modes. In Trig or Gate modes the waveform is clamped by the -2I+ current sources and the diode gate, at a point determined by the Start/Stop Phase control.

  • Page 7: Circuit Descriptions

    Circuit Descriptions Power Supply - Mains connections The operating voltage of the instrument is shown on the rear panel label. Should be it necessary to change the operating range from 220/240V AC to 110/120V or vice-versa, change the transformer connections following the appropriate diagram below. If a change is made, the operating voltage label and fuse should also be changed.
  • Page 8 Power Supply - DC Regulation Diodes D22 to D25 rectify the transformer output and C50 and C51 are the reservoir capacitors of the unregulated DC rails. Q34, Q35, Q36 and IC21a form the +15V regulator, Q34 and Q35 form the compound series pass element and Q36 its driver.
  • Page 9 When the symmetry button is depressed the short across VR8 is removed and the total resistance between Q1 and Q2 emitters is increased from R to 10R. This lowers the current through this resistor chain by a factor of 10 and so the frequency is divided by 10. Rotating VR8 imbalances the current through Q1 and Q2 to give a duty cycle of up to 1:19 or 19:1.
  • Page 10 Waveform Generation - Comparator and TTL output IC13 operates as a window detector and determines the peak to peak amplitude of the triangle wave on the range multiplier capacitor, which is approximately +/-1.2V. C17-C22 compensate for comparator and loop delays ensuring that the triangle wave amplitude remains constant with increase in frequency.
  • Page 11 Waveform Generation - Trigger Circuit In the Trig or Gate modes the waveform is clamped at the Start/Stop Phase point under control of IC14b (described earlier). Q19 and IC15b form a Schmitt trigger which ensures correct operation from DC to 5MHz. R71 and R72 with C27 fix the input threshold at <1.5V over the whole frequency range.
  • Page 12 Waveform Generation - Waveform Shaping The squarewave shaper is a diode bridge which steers current from either R89 or R90 into R91. This provides a squarewave with controlled rise/fall times, and thus no overshoot and ringing, which is symmetrical about ground. The drive signal comes from Q17. The sine shaper comprises a monolithic transistor array IC18 which is driven by the triangle amplifier.
  • Page 13 Output Amplifier and DC Offset The signal passes via the Amplitude control VR27 to the output amplifier. A simplified diagram is shown in fig. 7 and the following circuit description refers to this. The HF amplifier is made up of discrete components and is in principle an inverting operational amplifier with a gain of -10 set by R109 and R115.

  • Page 14: Calibration

    Calibration Equipment Required Oscilloscope Distortion meter 4.5 digit battery powered multimeter Calibration should be carried out after the instrument has been on for 1 hour. Note: If any work has been done to the output stage, VR32 and VR33 must be turned fully anti- clockwise before switching on.
  • Page 15 Sinewave amplitude - VR21 Squarewave amplitude - VR24 Triangle wave amplitude - VR25 DC offset of preamplifier - VR26 Output amplifier quiescent operating current - VR32 and VR33 Output amplifier dc offset - VR31 Output amplifier bias compensation - VR28 Output amplifier LF gain - VR30 +15Vrail - VR34 For best results the above adjustments should be carried out in the following manner:...
  • Page 16 that the voltage on these test points (TP14 and TP15) must not go below 13.3V otherwise Q28 and Q29 will be damaged. VR32 and VR33 are interactive. Connect a DVM to TP16 and check that the voltage on this point is <+/-1V. If not, slightly adjust VR32 or VR33 ensuring that the voltages on TP14 and TP15 remain within 13.4V to 13.5V.
  • Page 17 To help with trouble shooting the power supply etc., an external current limited (500mA) power supply of +/-17V can be used with its ground (0V) going to the TG501 ground (negative end of C50 or positive end of C51). The +17V supply is connected to the positive end of C50 and the -17V supply is connected to the negative end of C51.

  • Page 18: Parts List

    Parts List PCB Assembly - Main Description Part No 10RJ W25 CF 23185-0100 150KJ W25 CF 23185-4150 43KJ W25 CF 23187-3430 10KJ W25 CF 23185-3100 39KJ W25 CF 23185-3390 2K7F W25 MF 23202-2270 2K7F W25 MF 23202-2270 2K43F W25 MF 23202-2243 1K37F W25 MF 23202-2137...
  • Page 19 Description Part No 10RJ W25 CF 23185-0100 R35* 100RJ W25 CF 23185-1100 1K0J W25 CF 23185-2100 10KJ W25 CF 23185-3100 470RJ W25 CF 23185-1470 220RJ W25 CF 23185-1220 1K5J W25 CF 23185-2150 1K5J W25 CF 23185-2150 820RJ W25 CF 23185-1820 1K0J W25 CF 23185-2100 1K2J W25 CF...
  • Page 20 Description Part No 4K7J W25 CF 23185-2470 4K7J W25 CF 23185-2470 2K2J W25 CF 23185-2220 1K5J W25 CF 23185-2150 33KJ W25 CF 23185-3330 2K2J W25 CF 23185-2220 100RJ W25 CF 23185-1100 47RJ W25 CF 23185-0470 7K5J W25 CF 23187-2750 560RJ W25 CF 23185-1560 100RJ W25 CF 23185-1100...
  • Page 21 Description Part No R104 130KJ W25 CF 23187-4130 R105 82KJ W25 CF 23185-3820 R106 47KJ W25 CF 23185-3470 R107 22KJ W25 CF 23185-3220 R108 47KJ W25 CF 23185-3470 R109 470RJ W25 CF 23185-1470 R110 10KJ W25 CF 23185-3100 R111 560RJ W25 CF 23185-1560 R112 470RJ W25 CF...
  • Page 22 Description Part No R142* 3K3J W25 CF 23185-2330 R143 220RJ W25 CF 23185-1220 R144 1K0J W25 CF 23185-2100 R145 4K7J W25 CF 23185-2470 R146 1K2J W25 CF 23185-2120 R147 8K2J W25 CF 23187-2820 R148 5K6F W25 MF 23202-2560 R149 10KF W25 MF 23202-3100 R150 10KF W25 MF...
  • Page 23 Description Part No Preset 22K 23377-3220 Preset 10K 23377-3100 Preset 10K 23377-3100 Preset 10K 23377-3100 Preset 10K 23377-3100 Preset 10K 23377-3100 Preset 220R 23377-1220 VR10 Preset 10K 23377-3100 VR12 Preset 10K 23377-3100 VR13 Preset 10K 23377-3100 VR14 Preset 10K 23377-3100 VR15 Preset 1K0 23377-2100...
  • Page 24 Description Part No 10NZ 63V Cer 23427-0325 10NZ 63V Cer 23427-0325 10NZ 63V Cer 23427-0325 10NZ 63V Cer 23427-0325 150PF 630V P/S 23647-0515 1N8F 160V P/S 23646-0009 82PK 30V P/S 23646-0708 22NG 100V P/E 23620-0805 220NG 100V P/E 23620-0804 100NJ 100V P/E 23620-0207 4N7K 63V Cer 23427-0346...
  • Page 25 Description Part No 100NS 63V Cer 23438-0007 Not used 100NJ 100V P/E 23620-0207 1N0K 63V Cer 23427-0331 0.47UF 35V Tant 23594-0231 10UF 16V Tant 23594-0219 10UF 16V Tant 23594-0219 0.47UF 35V Tant 23594-0231 100NS 63V Cer 23438-0007 100NS 63V Cer 23438-0007 10UF 16V Tant 23594-0219...
  • Page 26 Description Part No Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio 1N4148 25021-0901 Dio BZX79C11 25130-0910...
  • Page 27 Description Part No Tran ZTX239 25380-0229 Tran ZTX214 25341-0214 Tran ZTX214 25341-0214 Tran ZTX239 25380-0229 Tran ZTX239 25380-0229 Tran ZTX214 25341-0214 Tran ZTX239 25380-0229 Tran ZTX239 25380-0229 Tran ZTX214 25341-0214 *Q10 Tran BF245A 25601-0103 *Q11 Tran BF245A 25601-0103 Tran ZTX214 25341-0214 Tran ZTX214 25341-0214...
  • Page 28 Description Part No Tran 2N3904 25381-0404 Tran 2N3906 25341-0218 Tran 2N3906 25341-0218 Tran BD239 25382-0500 Tran BC338 25383-0505 Tran ZTX550 25341-0215 *Q10 & Q11 are matched devices Description Part No LF441CN 27106-0621 LF441CN 27106-0621 LF441CN 27106-0621 LF441CN 27106-0621 LF441CN 27106-0621 LF441CN 27106-0621 TL071CP...
  • Page 29 Nut, M3 (for pot bracket (2)), for pcb bracket (2)) 4 off 20210.0101 PCB Support bracket 2 off 20663-0010 Screw M3 x 8mmL (for pcb bracket) 2 off 20234-0012 Adhesive pad (for C51,C52) 4 off 10300-0313 Terminal for T1 3 off 35311-0020 PCB, Main TG501/2/3 35555-0510...
  • Page 30 22588-0700 LED. 25061-0200 Adhesive pad for LED 10300-0313 Sleeve for LED wire 10232-0303 Solder tag, shakeproof (for earth wire) *20037-0400 Rear Panel Assy - TG501 Description Part No. Rear Panel *33331-0820 AC Mains Receptacle 22520-0120 Shroud for receptacle 22458-0004 Fuseholder...
  • Page 31 Description Part No. Screw M3 x 10mmL 2 off 20234-0011 Washer, shakeproof M3 (for Mains skt) 2 off 20037-0301 Washer, M3 (for Mains skt) 2 off 20030-0263 Nut, M3 Mains skt 2 off 20210-0101 Screw M4 x 8mmL (for Mains earth) 20234-0023 Solder tag, shakeproof 4BA (for earth wires) 2 off...
  • Page 32 Packaging Parts Description Part No Carton - TG501 *38114-0100 Load spreader for carton *38114-0105 End Cap for carton 2 off *20664-0170 Label, wiring instructions (for tinned ends Mains lead) 37541-0490 Mains Lead tinned ends 22491-0010 Mains lead Euro plug 22491-0020...