avo-160 电路图.pdf

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1、1 Re-edited by PD2MRX for adobe acrobat, 2004-2005. PA2MRX, from 2006. THE “AVO” VALVE TESTER Type 160 NSN: 6625-99-943-2419 WORKING INSTRUCTIONS SECOND EDITION PUBLISHED BY AVO LIMITED. AVOCET HOUSE, 92-96 VAUXHALL BRIDGE ROAD, LONDON, S.W.1 Telephone: VICtoria 3404-9 RadioFans.CN 收音机爱 好者资料库 2 THE

2、“AVO” VALVE TESTER TYPE 160. RadioFans.CN 收音机爱 好者资料库 3 FOREWORD For more then a quarter of a century we have been engaged in the design and manufacture of “AVO” Electric Measuring Instruments. Throughout that time we have consistently pioneered the design of modern multi-range instruments and have k

3、ept abreast of and catered for the requirements of the epoch-making developments in the field of radio and electronics. The success of our steadfast policy of maintaining high standards of performance in instruments of unexcelled accuracy, and making such instruments available at reasonable cost, is

4、 reflected in the great respect and genuine goodwill which “AVO” products enjoy in every part of the world. It has been gratifying to note the large numbers of instances where the satisfaction obtained from the performance of one of our instruments has led to the automatic choice of other instrument

5、s from the “AVO” range. This process, having continued over a long period of years, has resulted in virtual standardization on our products by numerous Public Bodies, The Services, Railway Systems, and Post Office and Telegraph Undertakings throughout the world. Our designers have thereby been encou

6、raged to ensure that new instruments or accessories for inclusion in the “AVO” range fit in with existing “AVO” apparatus and serve to extend the usefulness of instruments already in use. Thus, the user who standardizes on “AVO” products will seldom find himself short of essential measuring equipmen

7、t, for, be means of suitable accessories, his existing equipment can aften be adapted to meet unusual demands. It is with pleasure that we acknowledge that the unique position by “AVO” is due in no small measure to the co-operation of so many users who stimulate our research and Development staffs f

8、rom time to time with suggestions, criticism, and even requests for the production of entirely new instruments or accessories. It is our desire to encourage and preserve this relationship between those who use “AVO” instruments and those who are responsible for their design and manufacture, and corr

9、espondence is therefore welcomed, whilst suggestions will receive prompt and sympathetic consideration RadioFans.CN 收音机爱 好者资料库 4 THE “AVO” VALVE TESTER TYPE 160 CONTENTS Page Summery of Data .5 CHAPTER 1TECHNICAL DESCRIPTION 1Introduction.7 2 9Principles of operation .7 10 21Basic circuits.8 22 25Th

10、e Valve Holder Panel.13 26 General Construction.17 27Mains Supply.17 CHAPTER 2THE VALVE PANEL AND CONTROL UNIT 28 33The Valve Panel and Selector Switch.20 34 36Procedure for setting up Valve Base Connections.21 37Provision for new Valve Bases .23 38The Control Unit and its Function.23 39 41The Mains

11、 Voltage Selector.23 42 47The Circuit Selector.24 48The Electrode Selector .24 49The Heater Voltage Switches.24 50The Anode and Screen Voltage Switches.25 51 52The Anode Current Controls.25 53The Negative Grids Volts Control.26 54The Set mA/V Control .26 CHAPTER 3 OPERATING INSTRUCTIONS AND GENERAL

12、PROCEDURE FOR TESTING A VALVE 55The connection of the instrument to a supply voltage.27 56Final setting of Main Voltage Selector Panel.27 57 59Insulation checks with the valve cold .27 60 61Insulation checks with the valve hot.28 62Cathode to Heater insulation check.29 63 69Determination of valve co

13、ndition from Static Characteristic Data.29 70 71To check relative goodness of valve in conjunction with coloured comparison scale.30 (a) Using recommended anode current .30 (b) Using recommended negative grid voltage.30 72 73To check valve by direct reading of mutual conductance (mA/V) (a) Using rec

14、ommended anode current .31 (b) Using recommended negative grid voltage.31 74 75To check valves having a mutual conductance less then 1mA/V.31 76 77Measuring the grid current.32 78 84Checking Power Rectifiers.32 85Checking Signal Diodes.33 86Instructions for testing specific valve types.33 87 88Multi

15、ple Diodes and Rectifiers (D, DD, DDD, R, RR).33 89 91Diodes and Rectifiers combined with other electrode assemblies (DT, DDT DP, DDP, DTP).34 92Double Triodes and Double Pentodes (TT, TP) .34 93 97Frequency Changers (H, TH, O, TP).34 98 99The use of the links on the Valve Panel of the Instrument.35

16、 100Checking Tuning Indicators (TI).35 101Checking Gasfilled Rectifiers (GR).36 102Checking Cold Cathode Rectifiers (CCR).36 5 THE “AVO” VALVE TESTER TYPE 160 SUMMERY OF DATA Purpose A simple-to-use, double purpose Valve Tester with two functions: - (a) The rapid diagnose of the condition of a valve

17、 under test, the instrument operating as a simple “go” or “no go” device. (b) The production of sufficient data to enable an operator to plot static characteristics, or similar information, using selected anode loads. The instrument will check the majority of receiving valves, and some small transmi

18、tting valves. Description The instrument, which has been constructed to conform with appropriate clauses of the U.K. Government Climatic Tests K114, is housed within a metal carrying case. The case comprises two parts, the base containing the panel which carries the majority of the control, and the

19、lid, within which is housed the test panel for the valve under test. The instrument is supplied with a cable for connection to the mains. The majority of the 22 valve bases provided, accommodate valves on standard bases in common use, but in addition, disc-seal, co-axial and wire-ended valves can al

20、so be tested. A Nine Way Roller Selector Switch is provided to enable any valve pin to be connected to any electrode circuit. This Selector Switch is marked with figures and letters, the figures enabling code numbers to be set up from the “AVO” Valve Data Manual, whilst the letters signify the parti

21、cular electrode connected to the selected pin. The instrument control panel carries the following: - The Heater Volts Selector Switch. The Anode Volts Selector switch. The Screen Volts Selector switch. The Negative Grid Volts Control. The Mains Voltage Selector. The Fuse Carriers. The Visual Faults

22、indicator. The Indicator Meter. The Anode Current Controls. The Set mA/V (slope) Control. The Circuit Selector Switch. The Electrode Selector Switch The Mains ON/OFF Switch. Performance In addition to the detailed description of the instrument, contained in this Manual, abbreviated working instructi

23、ons are given as a preference to the “AVO” Valve Data Manual. 6 The instrument will: - (1) Check heater continuity. (2) Measure insulation between electrodes with valve cold. (3) Measure insulation between electrodes with valve hot. (4) Measure cathode/heater insulation (for directly heated valves)

24、(5) Rapidly indicate whether a valve is good or bad, use being made of a coloured replace/good scale with mutual conductance as a operative parameter. (6) Measure the mutual conductance (slope) of a valve, the applied incremental grid voltage being inversely proportional to the “slope” of the valve.

25、 (7) Measure anode current in single and multi-anode valves. (8) Produce sufficient data to enable static characteristic curves to be plotted on graph paper. (9) Check rectifiers and diodes under load conditions. (10) Measure gas current, limited to 100A. (11) Measure screen current. The instrument

26、is fitted with an automatic aural and visual warning device which operates if certain circuits within the instrument are inadvertently overloaded by the operator, or if a short occurs upon a valve under test. The use of specially designed circuits virtually eliminates the possibility of the valve un

27、der test bursting into spurious oscillation. Power requirements The instrument will operate from the following 50 500c/s AC supplies: - 105 120V, 175 250V (Adjustment can be made at every 5V.) Power consumption 50 Watts, maximum Physical data Weight:24 LBS. (11Kg.) (approx.) Height:10” (25,5cms.) De

28、pth:11” (29,5cms.) Width:15” (37,0cms.) Joint Services Designation “AVO” Valve Tester CT160. 7 CHAPTER 1 TECHNICAL DESCRIPTION Introduction 1. Whilst good/bad testing on a semi-production basis will undoubtedly be the major use of this tester, it is certain that the instrument will find considerable

29、 use in laboratories and service departments where engineers and skilled personnel will be available, and where more precise details of valve performance can be used to advantage. To this end, additional facilities on the tester, enable 1a/Va, 1a/Vs, 1a/Vg characteristics to be plotted over a wide r

30、ange of voltages, these being readily available from the calibrated panel controls. Principles of operation 2. The tester is basically designed to check the valve according to its static characteristics which would normally require the provision of the requisite range of variable DC supplies. The di

31、fficulty lies in the regulation problems involved in the supply of the wide range of DC anode and screen voltages, on which the loading might vary from a fraction of a mA to over 100mA, dependent on the type of valve being tested, and the provision of a number of regulated power supplies, which woul

32、d render the instrument cumbersome and expensive, whilst a large amount of metering, and would not only mean additional expense, but also make the instrument difficult to use, and would not entirely overcome the problem. 3. It can be shown, however, that if alternating electrode voltages are supplie

33、d in their correct proportions, an amplifying valve van (by virtue of its property of self rectification) be caused to give DC anode and screen currents which for all practical purposes bear a constant relationship to those obtained from its DC static characteristics. 4. This immediately simplifies

34、the problem of power supply to the valve under test. The design of transformers to give negligible regulation errors over the range of secondary currents involved is comparatively simple, whilst the range of electrode voltages may be simple provided by predetermined secondary tappings selected by ca

35、librated switches, thus minimizing to a very large extent problems of size, weight and cost, and eliminating the necessity for separate metering. 8 5. A slight difficulty occurs in the power supply of the variable negative grid bias valve. Which would normally consist of an alternating voltage of su

36、itable magnitude applied in anti-phase to the anode voltage. Since rectification occurs at the anode (and screen) and the grid should pass no current it will be readily seen that during the half cycle where the anode and screen are passing no current, a positive half cycle of considerable magnitude

37、is applied to the grid with the result that the latter can pass damaging current and in certain circuit conditions phase changes can occur that disturb the 180 relationship between the anode and grid voltages during the operative half cycle. 6. Since no current is taken from the grid voltage supply

38、however, and the voltages involved are not very high, the inclusion of a simple half wave rectifier without smoothing between the transformer winding and the variable grid volts supply will suppress the positive half cycle whilst still remaining the sinusoidal form of the operative negative half cyc

39、le. 7. Using the simple expression for anode current of a triode Ia = K/Ra (Ea : Eg) and transforming this for AC operations on the positive half cycle of applied anode volts we have:- 8. Deriving this in terms of RMS applied voltages and remembering that anode current flows only on the positive hal

40、f cycle and will be read on a mean reading DC meter, we have:- E.g. (DC) is the applied half sine wave DC as read on a mean reading DC voltmeter, K being a constant. The above relation holds equally well for screen grid of pentode valves, which would allow the general form 9. Thus with an applied RM

41、S anode (and or screen) voltage equal to 1*1 x Va(DC) and mean value of half wave rectified bias voltage equal to 0*5 x VG (DC) then the valve will read a mean DC anode current equal to one half of the DC anode current taken from the static characteristics if Va (DC) and VG (DC) were applied DC test

42、 volts. This relationship holds for all practical purposes over the full characteristics and is the basis of operation of the VT160 enabling accurate testing of valves, at any point on their characteristic, with simple and small apparatus. This accuracy is just as necessary on the simple “go”/”no go

43、” type of instrument as a complete characteristic meter, as it may be necessary to set the test point anywhere on the characteristic to correspond to required working condition. Further in the absence of any printed or predetermined test figure, it must be possible to determine test conditions direc

44、tly from manufacturers published curves of data. Basic circuitry 10. The principles of operation of the main function of the tester the comparative testing of mutual conductance lie in the application of anode, screen and heater voltages corresponding 9 to the working point of the valve and backing

45、off to zero the standing anode current thus obtained. A small incremental bias is applied to the valve and the change in anode current thus obtained is a measure of the mutual conductance of the valve. The figure is then compared with the correct mutual conductance to give comparative goodness on a

46、coloured scale. FIG. 1. BASIC CIRCUIT FOR CHECKING OF MUTUAL CHARACTERISTICS 11. figure 1 shows the fundamental circuit used in this measurement. With a requisite electrode voltage applied to the valve, the half wave anode current causes a voltage drop in resistor RL, which is sufficiently low resis

47、tance not to influence the characteristics. This voltage is backed off by a voltage of similar form from the Control Vb. The voltage difference across the two arms of the bridge thus formed is shown on the DC millivoltmeter M. When this difference is zero, the voltage Vb is a measure of the anode cu

48、rrent in RL (Ia = V/RL) and the control Vb is thus calibrated in mA anode current. A small change in bias is then applied to the valve from control dVg which causes an increased voltage drop in RL which unbalances the bridge. This unbalance is shown on M and is a measure of the mutual conductance of the valve. For a deflection on M of RL millivolts then the mutual conductance of the va