AVO CT160 Operating Instructions THORN
Contents
1. 7 The measurement of control grid current on a scale directly calibrated in 4A 8 The testing of half and full wave rectifiers under reservoir capacitor conditions with a range of dc loads which can be selected by means of a switch 9 The testing of signal diodes with suitable dc loads which can be selected by the operator 10 The testing of the separate sections of multiple valves the non operative section of the valve under test being maintained at reasonable working electrode voltages 11 The ability to derive data from which the characteristic curves la Vg la Va Vg Vg2 etc can be drawn with a range of applied electrode voltages cor responding to dc operating conditions 12 The testing of valves with suitable loads included in the anode circuit together with the ability to read the required electrode current on a separate external meter The instrument is therefore suitable for making tests on non standard and specialised types of valves not catered for in normal circuit arrangements The function of the various controls is as follows The Mains Voltage Selector 39 The instrument has been designed to operate from supplies of 50 500c s over the following voltage ranges 105 120V 175 190V 195 210V 215 230V 235 250V 40 Access to the Voltage Selector Panel can be gained by turning a thumb screw and lifting the transparent cover The Coarse Voltage Selector is marked 110 180 200 220 and 22. Measure insulation between electrodes with valve hot Measure cathode heater insulation for indirectly heated valves Rapidly indicate whether a valve is good or bad use being made of a coloured replace good scale with mutual conductance as the operative parameter Measure the mutual conductance slope of a valve the applied incremental grid voltage being inversely proportional to the slope of the valve Measure anode current in single and multi anode valves Produce sufficient data to enable static characteristic curves to be plotted on graph paper Check rectifiers and diodes under load conditions Measure gas current limited to 1004A The instrument 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 eliminate the possibility of the valve under 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 Ibs 11 kg approx Height 10 255 mm Depth 114 295 mm Width 154 370 mm Joint Services Designation AVO Valve Tester CT160 CHAPTER 1 TECHNICAL DESCRIPTION Introduction
3. 1 Whilst good bad testing on a semi production basis will undoubtedly be the major use for this tester it is certain that the instrument will find considerable 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 Ia Va Ia Vs and Ia Vg characteristics to be plotted over a wide range 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 charac teristics which would normally require the provision of the requisite range of variable dc supplies The difficulty 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 100 mA dependent on the type of valve being tested and the nature of the test being performed Such a requirement could of course be met by the provision of a number of regulated power supplies which would render the instrument cumbersome and expensive whilst a large amount of metering 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 applied in their correct propor
4. 30 APPENDIX I THE AVO VALVE TESTER TYPE 160 Schedule of Spare Parts INTRODUCTION Throughout the past decade the Avo Valve Tester Type 160 has proved itself to be unrivalled for versatility and reliability It is however inevitable that this instrument will fail from time to time and when it does we are anxious to ensure that it is repaired to the highest possible standard We have therefore produced this schedule of spares which will form a useful guide to the trained engineer who has the task of servicing this instrument Procedure for ordering spare parts If you will kindly follow the procedure set out below delays will not occur due to the exchange of unnecessary correspondence 1 State the part number of the items required also the quantity 2 State the serial number of the instrument This will be found on an identification label attached to the instrument 3 When ordering spare parts for the movement assembly the movement serial number must also be stated Overseas users of our instruments should send their requirements to our Agents on their territory If the spares are required for use in Great Britain application should be made direct to our Spares Department 32 Item Part Circuit Qty No No Description Ref off 1 40508 B Complete Case Assembly l 2 40508 BI Case Top Assembly l 3 40508 B2 Case Bottom Assembly I 4 40462 A Chassis Assembly see below for breakdown details o I 5 1
5. DDD refers to a triple diode Multiple Diodes and Rectifiers D DD DDD R RR 87 The testing of Multiple Diodes and Rectifiers is carried out in the manner already explained the ELECTRODE SELECTOR being used to select the diode or rectifier element the emission of which is indicated on the meter replace good scale When dealing with diodes or rectifiers the D and D gt positions of the ELECTRODE SELECTOR represent diode or rectifier anodes 1 and 2 respectively and correspond to figures 8 and 9 on the ROLLER SELECTOR SWITCH set up number SR 88 In the case of Triple Diodes since only two anode systems are normally catered for a special procedure is adopted in the set up figure At the position in the SELECTOR SWITCH number representing the third diode the symbol j is included The first and second diodes being indicated by 8 and 9 respectively in the normal manner The valve should now be tested normally with the ROLLER SELECTOR SWITCH set to 0 where the appears in the set up number This procedure will give emission figures for diodes 1 and 2 Now rotate the ROLLER SELECTOR SWITCH rollers so that the two rollers originally set at 8 and 9 are now set to 0 and set the pin marked f in the Valve Data to 8 on the ROLLER SELECTOR SWITCH A further test with the ELECTRODE SELECTOR Switch at D will then give the emission of the third diode e g EABI is indicated in the data as 023 110 890 To test diodes and 2 the
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7. ORERATING INSTRUISMONS VALVE TESTER TYPE 160 CONTENTS Summary of Data CHAPTER 1 1 2 9 10 21 22 25 26 27 CHAPTER 2 28 33 34 36 CHAPTER 3 55 56 57 59 60 61 62 63 69 70 71 APPENDIX 1 TECHNICAL DESCRIPTION Introduction Principles of operation Basic Circuits The Valve Holder Panel General Construction Mains Supply THE VALVE PANEL AND CONTROL UNIT The Valve Panel and Selector Switch Procedure for setting up Valve Base Connections Provision for new Valve Bases e The Control Unit and its Function The Mains Voltage Selector The Circuit Selector The Electrode Selector The Heater Voltage Switches The Anode and Screen Voltage Switches The Anode Current Controls ES The Negative Grid Volts Control The Set mA V Control eg Page OPERATING INSTRUCTIONS a GENERAL PR PROCEDURE FOR TESTING L The connection of the instrument to a supply voltage Final setting of Mains Voltage Selector Panel Insulation checks with the valve cold Insulation checks with the valve hot Cathode to Heater insulation check Determination of valve condition from Static Characteristic Data oe relative goodness of valve in conjunction with coloured comparison scale Se e W EN E a Using recommended anode current ee y b Using recommended negative grid voltage To check valve by direct reading of mutual conductance mA V a Using recommended anode curren
8. until the meter reads full scale deflection at which point the grid voltage and therefore all the other voltages working the instrument are correctly proportioned FIG 3 17 The full circuit diagram shows how all the above combinations are incorporated in a single circuit and selected by appropriate switch settings Despite the full range of test voltages available and the comparative complexity of the circuit the discreet use of ganged controls has reduced the operation to a simple and logical sequence 9 18 Figure 4 shows in diagrammatic form the panel marking and it will be seen there from that in addition to the controls supplying the appropriate electrode voltages only three controls are really involved in a measurement The CIRCUIT SELECTOR rotates through the various insulation checks to position TEST at which point the circuit is operative for mutual conductance testing by backing off with the ANODE CURRENT controls and by setting control SET mA V at which point the meter shows the valve goodness Separate electrode systems of dual or multiple valves are measured by setting the ELECTRODE SELECTOR to Al or A2 With this switch to D1 or D2 the circuit is ready for rectifier or signal diode testing with the CIRCUIT SELECTOR at TEST The selection of load current is made by rotating the anode current control also separately scaled in rectifier load current to the appropriate position valve goodness being immediately shown on t
9. 39 Spring Washer 6BA double coil 1 39 091 SdA J91S9 IAJE A OAV JOJ WeIseIG MNO O OSZE VIOE tI ZO H yu o 0 O wuwoss 10 sv g u s gt wort vO ywodY lv f 1S31 2 w v G YuQz Y vuoi Y qY 2 H 2 q LNOD H Z Ot wworu vu Og 7 who WH 92 s 135 t OQ YuOp 9 v u Ob I MS MOLE 300812313 JO SNOILISOd A S 6O12313S LINDYID JO SNO ILISOd OMS YO 21 135 i SNOILSOd 291 H H ICOHIVI 1 0 0 0 00 19109 L Oo O Y dd LA 005 JO AO 2 XO INdN SNIViW ee o alate Q ll ERES E A a J y A me am Esos y vi 3 gt e lad lt w lt s aen b gt gt i gt gt i gt agens AZOO ALLAAH ARAO gt gt af wi o KAA 1 3QONY 30ONV t 30010 1 390010 XA b YO1D3973S 2 300813313 _ a oH YOLDIWS LINDWID AO A LA zg mr em we amp w ze mm ms nm mm e r He ep ep LASS d u DOO W K OMS gt a e OAV Aq punoAd394AO CM III A V d L GAN PM FTF 1O1sISoq PUNOAA ITAA SNOOITIA CME TI9E VY SGA UAM PAA Z F OIA uoqieO NTIqe s 910 Y EZ F mq aoge sy CA 1 III A V SdAL UAM PM S ISIA punoAA IAA SNODIHA CM FE EZIEV od L DAADAA 1NQ IAOQB SY TIO Y Sd J U M PM lt 107SISIY uoqieO NIQUIS SI 2 d L C L poy A007 MS I Veo AS dure z dure Z
10. Corresponds to the second Diode Anode of Signal Diode and Rectifier valves Diode D and Rectifier Amplifier combinations 0 Corresponds to a dis connected valve pin or to a pin on which an internal electrode is anchored Such pins are marked I C in Manufacturer s literature This switch position leaves the particular valve pin dis connected from any circuit Some instruments will be found to be fitted with rollers marked regarded as being synonymous with which can be Procedure for Setting up Valve Base Connections 34 The procedure for setting up a valve ready for test is as follows From some suitable source i e the AVO Valve Data Manual Valve Manufacturer s Data Leaflet or any other Manual of Valve Data determine the pin basing connections for the valve Rotate the roller of the SELECTOR SWITCH until the code number or electrode letter combination appears in the window reading from left to right in accordance with the standard pin numbering sequence see Fig 5 When a valve has less than 9 pins the free rollers on the right of the set up combination corresponds to non existent valve electrodes and should be set at 9 Insert the valve into its appropriate holder following the sequence laid down in the general procedure for testing a valve section 55 and by means of the lead provided connect any top cap or side connection on the valve to its appropriate socket on the socket panel Note that the
11. Loctal Valve Holder which has only 8 normal electrodes has its centre spigot connected to the ninth roller corresponding to Pin No 9 to accommodate valves which have a connection made to this spigot 35 The accompanying examples show how to correlate the pin basing data and the equivalent code number for various valves in common use 15 Valve Type Roller selector Switch Code Osram MH4 indirectly 4 2 3 1 heated triode A G H H C British 5 pin base ON 0 0 0 0 Osram U50 full wave 0 2 0 8 0 90 3 O rectifier directly heated H Dl D2 H International Octal Base Mullard Pen A4 ine O 4 5 2 3 16 0 O directly heated output G S H H C A pentode British 7 pin base Brimar 6K8 indirectly 0 2 7 5 4 6 3 1 0 heated frequency H A2 S G A H C changer Top Cap G1 International Octal Base Mullard TDD2A battery 6 8 2 3 9 0 0 0 O double diode triode A Di H H D2 British 5 pin base Top Cap Gl Mullard EFSO indirect 2 56 1 0 1 4 O 3 ly heated HF pentode H S A C C G H B9G base Note Base Diagram 36 When the SELECTOR SWITCH setting is derived from manufacturers Data and a pin connection is shown as I C internally connected the roller appertaining to this pin should be set to 2 Where a pin connection is an electrode normally connected to cathode e g G3 the roller corresponding to this pin should be set to 16 Pro
12. set up on the ROLLER SELECTOR SWITCH will be 023 100 890 enabling these diodes to be tested in the normal manner To obtain the emission figure for the third diode the SELECTOR Switch should be altered to read 023 180 000 and the ELECTRODE SELECTOR set to position D Diodes and Rectifiers combined with other Electrode Assemblies DT DDT DP DDP DTP 89 Combined diode and amplifying valves are represented in the type column of the Data by DT and DDT for diode triodes and double diode triodes whilst DP and DDP indicate diode pentodes and double diode pentodes 90 The testing of the separate sections of each valve is carried out in rotation the amplifying sections being tested first with the CIRCUIT SELECTOR at TEST and the ELECTRODE SELECTOR at position Aj 91 The rotation of the ELECTRODE SELECTOR to the D or D position will automatically set the instrument in readiness for testing one or both diodes with the right hand ANODE CURRENT control set to 1 on the inner scale Double Triodes and Double Pentodes TT PP 92 Double Triodes or Double Pentodes are indicated by the letters TT or PP each section being tested in the normal manner the selection of each assembly being made by the rotation of the ELECTRODE SELECTOR Switch to A and A corresponding to the ROLLER SELECTOR SWITCH numbers 6 and 7 When double valves are used in Class B or balanced circuits a close match cf the
13. the scale The proportionate deflection on the coloured scale denotes the state of the valve as before Switching of anode voltage meter range and load is ganged so that rectified currents of 1 mA 5 mA 15mA 30 mA 60 mA and 120 mA per anode are available each anode of a full wave rectifier being tested separately The 1 mA and 5 mA ranges are suitable for signal diode testing Ca iene 16 For the checking of inter electrode insulation figure 3 the unidirectional grid voltage Vg is applied through the meter M suitably loaded by a shunt s and high series resistor R across the electrode groups between which the insulation 1s to be measured Vg S and R are such that the first meter indication is at 25 M Q full scale of course representing a dead short The meter is suitably scaled for direct reading between these limits This test serves for heater continuity and insulation measurements between anode and all other electrodes strapped and screen and all others with the valve cold With heater volts applied the normal cathode heater test is made whilst a further test of cathode and heater strapped rest takes care of sagging grids or filaments of directly heated valves Since a short circuit deflection is in fact a measure of the grid voltage this is used in checking the setting of the mains voltage of the instrument at position Set In this condition a short is put on the insulation test circuit and the mains selector is adjusted
14. the panel adjacent to the appropriate socket It is assumed that all flying lead valves will be inserted into the appropriate Valve Holder with the envelope pointing downwards and the wire connections uppermost corresponding to the normal method of designating valve pin numbers looking into the valve pins 30 All Valve Holders are wired with their corresponding pins in parallel i e all pins numbered 1 are wired together all pins numbered 2 and so on This wiring combination is associated with the well known AVO MULTI WAY ROLLER SELECTOR SWITCH which enables any one of the nine standard pin numbers to be connected to any one of the electrode test circuits in the instrument thus enabling any electrode combination to be set up for all Valve Holders 31 It will be seen that the Selector Switch comprises nine thumb rollers numbered from left to right 1 9 This numbering appears on the moulded escutcheon immediately behind the rollers and corresponds to the valve pins in the order of their standard pin numbering Thus valves with any number of pin connections up to nine can be accommodated To cater for Top Cap and other external valve connections a socket panel has been provided with nine sockets marked D1 D2 A2 Al S G H H amp C A short lead is provided which is fitted with a plug for insertion into the panel whilst the remote end of the lead is fitted with a universal connection clip to cater for all types of external
15. 11310 B 14732 2 14273 1 14746 11673 3 14750 2 14747 1 13561 1 14739 2 14745 2 VALVE PANEL ASSEMBLY 40510 Description Valve Holder UX6 Valve Holder UX4 Valve Holder UX7 large Valve Holder UX7 small Valve Holder UX5 Valve Holder Mazda Octal Valve Holder British 9 pin Valve Holder B7G Valve Holder B8A Valve Holder 8 pin side contact Valve Holder BIA Valve Holder BBG Valve Holder British 4 5 pin Valve Holder International Octal Valve Holder BIG w Valve Holder British 7 pin Valve Holder B3G bai Escutcheon for item 22 Grommet Roller Selector Switch Top Cap Escutcheon Ceramic Valve Holder Segment Bakelite Washer for item 24 Valve Holder Spring Assembly for item 24 Valve Holder Spring Assembly ene for item 24 Bakelite Washer for item 24 Collar for item 24 Valve Holder Panel Warning Label Tag Board ER Plug Block I Tool Clip Identity Label Pillars for item 32 bal Pillars adjacent to item 22 Ferroxcube Bead Insulating Plug for item 37 Special Screw for item 37 Warning Label 38 Circuit Ref Qty off KNOB ASSEMBLY 15220 A Item Part Circuit Qty No No Description Ref off l 14267 1 Knob I 2 14268 4 Knob Skirt silver with marker line 1 3 14266 6 Knob Carrier a ee ie l 4 14269 4 Retaining Nut l 5 150662 Knob Washer between items 2 amp 4 1 6 20245 52 Spring Dowel pi s I 7 sS 745 Screw knob securing I 8 W
16. 40 whilst a Fine Voltage Selector Arm is marked 5 0 5 10 The setting on this Fine Voltage Selector must be added to the voltage marked under the socket Into which 17 the selector pin has been inserted For example if it is desired to operate the instrument on a 230V ac supply the Coarse Selector Pin should be screwed into the 220V socket and the Fine Selector Arm turned to its 10 position 41 The Fine Voltage Selector also allows minor adjustments to be made to the input tappings on the mains transformer to compensate for voltage variations of the mains The instrument should be switched off whilst adjustments are made to the Coarse MAINS VOLTAGE SELECTOR NOTE If the instrument is intended for use on 110v the red warning lamp LP2 should be replaced with a 110v version The Circuit Selector 42 This is an eight position switch which determines the type of test to be undertaken on the instrument All the necessary internal circuit connections are made automatically to satisfy the test conditions required whilst internal test circuits unnecessary to the particular test in hand are removed from the valve 43 The switch position SET enables final mains voltage adjustment to be made At the H CONT position the meter indicates helater continuity At the positions A R and S R and used in conjunction with the ELECTRODE SELECTOR Switch it is possible to check leakage between electrodes with the valve heater cold 44 A
17. 4740 4 Metal Foot for item 2 4 6 14740 3 Metal Foot for item 3 4 7 13714 3 Spacing Washer for items 5 amp 6 8 8 40374 2 Gasket for Valve Panel Assembly l 9 40510 A Valve Panel Assembly see page 44 for breakdown details I 10 40507 1 Seal between items 3 amp 4 l 11 20970 A Hinge Assembly 2 12 20970 B Clasp Assembly I S 2 13 14635 3 Release Block for item 12 2 14 14011 1 Mains Lead l 15 11237 E Top Cap Lead 2 16 14746 Identity Label 1 17 11727 5 Handle Clamp 2 18 14555 1 Dust Excluder l 19 11727 A Handle Assembly 1 20 115961 Rubber Foot 4 21 14773 2 Rubber Foot Support 4 CHASSIS ASSEMBLY 40462 A Item Part Circuit Qty No No Description Ref off 1 Negative Grid Volts Assembly see page 40 for breakdown details l 2 15220 A Knob Assembly see page 45 for breakdown details 7 3 40650 B Movement Assembly Es page 41 for breakdown details d eg 1 4 40471 A Mains Adjuster l 5 14627 2 Cover for item 4 l 6 40465 A Mutual Conductance Control Assembly see page 42 for breakdown uct E l 7 14663 2 Indicator Pillar 1 8 45330 5 way Connector Lead l 9 13845 3 Handle 2 MAIN ASSEMBLY 40508 C Item No 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 39 Item Z 00 1 ON CA a NN Part No 13846 5 N 82 20888 1 20967 A 14274 1 13701 9 10266 1 14558 2 40464 A 20909 1 14822 3 12239 6 12049 89 12049 88 50010 14 13
18. 698 1 20911 1 13657 1 14010 1 14822 2 20911 1 40468 2 11310 A 20901 B 20892 1 20899 B 20908 A 40466 A 14653 1 Part No 14267 1 S 745 W 39 14670 2 20245 52 1471 1 2 14275 2 13908 2 CHASSIS ASSEMBLY 40462 A Contd Circuit Description Ref Handle Bush for item 9 Stiff Nut End Frame Component Board Assembly see page 42 for breakdown details L Shaped Mounting Bracket Movement Mounting Pillar 2BA Tag for item 15 Anode Current Potentiometer RV4 Anode Current Switch see page 43 for breakdown details e 89 Electrode Selector Switch 2 Ge S Circuit Selector Switch Ka SN Sa r Fuse 2 amperes i F1 F2 Fuse Holder Fuse Holder Cap Indicator Lamp 6 3V 0 3A LPI Indicator Lamp Assembly complete i Screen Volt Switch I y S pe A Toggle Switch SS E e SI S2 Input Plug 7 Ss SA NW ge Heater Volt Switch me sch Si Ss Anode Volt Switch Sa we Ss S Front Panel of be KS Tag Board Assembly SE De D L T Transformer Assembly gi ae gon A2 Transformer Angle Sg oe S H T Transformer Assembly d ig Ti Lamp Board Assembly Relay Assembly see page 43 for breakdown n details Lamp 200V red for item 36 E NEGATIVE GRID VOLTAGE CONTROL Circuit Description Ref Knob Screw 6BA Tin plated Coiled Washer 6BA Knob Carrier Spring Dowel Spindle Bush Hexagonal Locknut 34 Qty off NAD HN N A bech w ke IN bes bech
19. LECTRODE SELECTOR at Az See also comments under Testing of Specific Valve Types Note 3 Certain valves require an exceptionally long period to reach working temperature the symptoms being a continual rise of anode current when the SET mAJV dial is at the SET ZERO more sensitive position Slope measurements should not be taken until a condition of stability has been reached 25 Note 4 When checking certain valves of the CV 138 type back emission sometimes occurs between the anode and the suppressor grid which is normally connected to cathode This condition which is caused by local overheating of the anode would not affect the operation of the valve under normal circuit conditions although it could give rise to doubt as to the goodness of the valve when checked on a valve testing instrument The phenomenon shows itself as an apparent gradual fall in anode current as the valve heats up and the only manner in which this effect can be overcome is to lower the power dissipation of the valve by reducing the anode voltage Note E in the AVO Valve Data Manual relates to the above conditions and a note appears against those valve types concerned together with an alternative set of test data Note 5 In literature issued by American Valve Manufacturers the term transconductance is used in place of mutual conductance Transconductance given in micromhos divided by 1 000 gives mA V Transconductance
20. Micromhos mA Y _ _ 1 000 Measurement of Grid Current 76 The measurement of grid current at a desired set of electrode voltages may be made after having measured the mutual conductance of a valve This measurement should not be made where an apparent fault in the valve has previously caused the protective relay to operate possibly due to softness 77 The CIRCUIT SELECTOR switch should be set to GAS thus inserting the meter into the grid circuit of the valve where it records grid current directly in yA The meter is limited to read a maximum of 100uA but it is not possible to state the value at which a valve becomes useless due to the presence of gas The point at which gas current reaches a value great enough to affect the successful employment of the valve depends very much upon the circuitry in conjunction with which it is to be employed e g it is possible for appreciable grid current to flow in the secondary of an r f transformer connected between grid and earth but if resistance capacity coupling is used in the circuit the same magnitude of grid current may produce appreciable voltage across the bias resistor thus completely upsetting the normal functions of the circuit Checking Power Rectifiers 78 The testing of rectifying valves should ideally be associated with the requirements of the circuit in which they are to operate In most cases throughout the AVO Valve Data Manual the figure quoted denotes the stand
21. RAL PROCEDURE FOR TESTING VALVE The connection of the instrument to a supply voltage 55 Remove the mains supply lead from its storage position in the lid of the instrument and connect the cable termination to the socket provided on the control panel Ascertain the voltage of the mains supply which must of course be 50 500c s and set the MAINS VOLTAGE SELECTOR panel as described in Chapter 2 Connect the mains lead of the instrument to the power supply ensuring that the red wire is connected to line the black or blue wire to neutral and the green wire to earth Set the MAINS Switch on the panel to its ON position and observe that the panel indicator lamp is illuminated The valve to be tested should NOT be inserted at this stage Final setting of Mains Voltage Selector Panel 56 Having allowed a few moments for the instrument to warm up set the CIRCUIT SELECTOR Switch to the position SET lt Set the fine voltage adjustment control so that the meter needle lies in the black zone If this cannot be done the coarse control will require adjustment and should be moved to the next higher tapping if the needle is too far to the right of the mains adjustment zone and in a similar manner it should be moved to the next lower tapping if the meter needle is to the left of the mains setting zone Once the mains voltage tapping has been correctly set provided that extensive mains fluctuations do not occur test vo
22. aker s rating for maximum load current can be used as the basis for the setting of the ANODE CURRENT switch 84 In the case of full wave rectifiers each anode of the valve is rated independently and the setting of the ANODE CURRENT control should indicate half the total value of the current which the valve would be expected to deliver in a full wave rectifier circuit e g a valve rated at a maximum of 120mA would be tested with each anode at the 60 position on the ANODE CURRENT control The load rating given in the Valve Data Manual is the load per anode Checking Signal Diodes 85 Signal Diodes are checked in exactly the same manner as rectifiers except that the right hand ANODE CURRENT control is always set to 1 or 3 according to the anode current figure given in the Data Where AVO Valve Data does not give a current figure for a diode it is always checked with the right hand ANODE CURRENT control set to its ImA position INSTRUCTIONS FOR TESTING SPECIFIC VALVE TYPES 86 The functions of a valve as distinct from the type number given to it by its manufacturer is indicated by a symbol in the form of letters appearing at the right of the test data given in AVO publications e g a half wave rectifier is marked R whilst a full wave rectifier is designated by RR Ina similar manner diode valves are shown by the letter D the number of diode elements being indicated by the number of Ds e g
23. ard emission per anode to be expected from the type of valve under test 79 The procedure for testing a rectifying valve is exactly the same as that for a valve with one or more grids to the end of the insulation checks 80 From this point onwards before setting the CIRCUIT SELECTOR to the position TEST the right hand ANODE CURRENT control switch reading on the inner set of figures should be set to the load current given for the valve in the Valve Data 26 Manual Set CIRCUIT SELECTOR to TEST and the ELECTRODE SELECTOR either to D in the case of a half wave rectifier or D and D for a full wave rectifier 81 Having correctly set up the controls as explained above the goodness factor of the valve under test will be shown on the coloured replace good scale of the meter 82 The inner ring of figures on the ANODE CURRENT Control relate to load currents and are marked Diodes and Rectifiers the figures marked being the emission in mA expected per anode of the valve under test 83 The setting of this control can either be determined from the tabulated data given or can alternatively be related to the total current that a valve is required to deliver Thus on a piece of equipment where the total h t drain on the rectifier is 50mA then a rectifier load setting of 60 will be an adequate test of the valve s emissive state assuming that it is a half wave rectifier Alternatively if the valve is a new one the m
24. bech L bh E IN 2 bes Qty FR baa bech y bech k b i bech Item No 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 Item Z m DO GO zl A Ur T 2 Ne kuch NEGATIVE GRID VOLTAGE CONTROL Contd Part No 14631 3 W 3 14669 2 N 77 14630 1 S 867 14559 2 13920 2 A 1510 14632 4 S 869 13917 2 14560 1 5 740 14710 2 13843 10 14557 1 14558 1 Part No 40537 2 40538 A 12730 2 30006 W 14824 3 21124 D 10194 B 10184 B 10191 4 10158 4 10075 16 Circuit Description Ref Friction Washer Washer 4BA Collar Hexagonal Locknut 4BA Tinplated Cover Instrument Head Screw 8BA Negative Grid Volts Dial Dial Flange Cheesehead Screw 4BA Tinplated Friction Disc Countersunk Screw 8BA Tinplated Clamp Plate Cursor Cheesehead Screw 6BA A Tinplated Pillar z Pillar Potentiometer Strap a T ei Potentiometer S d WW K RV2 MOVEMENT ASSEMBLY 40650 B Circuit Description Ref Moulded Front Cover Moulded Case Rear Window Glass Swamp Bobbin Scale Plate Moving Coil Assembly complete Fixed Jewel Assembly e Sprung Jewel Assembly Zero Adjuster Pivot Hair Spring 35 o r wet PY IN ND bet LA LN Fa L d reg FQ Fa Fa E Qty R MO NO Fei Feet pi Feat Feet w Fe Item No ege ON 00 A Un Qe UY Fa j Wn amp Who Item No O 00 zl ON Q L
25. cathode temperature will result in a higher percentage change in emission 96 When a valve is oscillating it tends to run into the positive grid region thus making full use of the emissive capabilities of the cathode and failing emission may well prevent oscillation taking place As a subsequent test therefore it is helpful to note the anode current at the rated test figures with the normal heater voltage applied and then to decrease the heater voltage by about 15 for a short period It may be necessary to operate the HEATER VOLTAGE TOGGLE SWITCH to give the necessary decrease in voltage In the case of a valve with failing emission the decrease in cathode temperature will result in an excessive decrease in the anode current considerably greater than the percentage decrease in heater voltage Such a result would suggest that the valve will not oscillate satisfactorily Conversely a negligible or small decrease in anode current or of the same order as the percentage change in heater volts will show that the valve is developing its full emission at the rated heater voltage and provided that the circuit conditions are correct it should oscillate normally 97 Frequency Changers Employing Separate Electrode Assemblies for oscillator and mixer functions are designated by TH triode hexode and TP triode pentodes The separate sections of this type of valve are not interdependent as in the case of the phantom cathode types m
26. characteristics of both halves is essential Frequency Changers H TH O TP 93 Frequency Changers of the Heptode and Hexode classes employing the normal oscillator section as a phantom cathode for the mixer section are not very satisfactorily tested in two sections since the nature of the valve construction is such that each section is dependent upon the other for its correct operation For test purposes therefore this valve is shown connected as a pentode or triode for which where possible anode current and or mutual conductance figures are given Such valves are indicated by the letter H in the type column 94 An exception to this type of valve is the Octode designated by O in the type column which as will be seen from the Data is normally tested as if it had two separate electrode assemblies separate data being given for each In this case the oscillator section is tested with the ELECTRODE SELECTOR Switch at A and the mixer section at A 28 95 As a further test to ensure the probability of such a valve oscillating satisfactorily an indication of failing emission will probably give the most useful results When a valve is perfect its cathode will develop its full emission at the rated heater voltage and any change in the cathode temperature will result at the most in a corresponding percentage change in emission If however the emission of the cathode is failing then an increase or decrease in the
27. ches the calibration line in centre of good zone marked 1mA V iv Read actual value of mutual conductance from SET mAfV dial This figure can be compared with that given in Data Manual 73 b Using recommended negative grid voltage 1 Do not alter NEG GRID VOLTS control but adjust ANODE CURRENT controls until meter is balanced to zero 11 Slowly rotate SET mA V control to SET ZERO position and make any final adjustment to zero using fine ANODE CURRENT control See Note 3 111 Continue rotation of SET mAfV control until meter needle reaches the calibration line in centre of good zone marked ImAfV iv Read actual value of mutual conductance from SET mA V dial This figure can be compared with that given in the Data Manual To check Valves having a Mutual Conductance less than ImA V 74 Since the SET mA V dial is not calibrated below 1mA V it is not possible to check on the coloured comparison scale valves having an expected mutual conductance less than ImA V Such valves are checked by direct measurement of mutual conductance using the procedure set out in paragraphs 72 or 73 with the exception that the mA V dial is rotated to the ImA V position and the actual value for mutual conductance being less than ImA V is read on the meter scale calibrated 0 1 ImA V 75 For valves with more than one electrode assembly having set up for any difference in electrode voltages repeat above test with E
28. circuit in figure 1 is to prevent erroneous results and possibly valve overheating and damage that can occur when testing certain beam tetrode valves with alternating anode and screen voltages 14 As the applied electrode voltages approach zero during a portion of the operative cycle the focusing of the electrode beam is to some extent upset with the result that the screen current decreases and rapidly becomes negative with consequent rapid and continuously increasing anode current The rectifier whilst presenting negligibly low forward impedance to normal screen current by virtue of its high reverse impedance successfully prevents the flow of reverse screen current ww E E EE EN D t D e e e D Va Rr e P D VVQVYVYVQOQVYIVVII CU FIG 2 BASIC CIRCUIT FOR THE TESTING OF RECTIFIERS AND SIGNAL DIODES 15 Figure 2 shows the basic circuit of the rectifier test The rectifier is loaded with a resistor RS RL and a reservoir capacitor C in parallel Sinusoidal voltage Va is applied of sufficient magnitude to operate the rectifier on the linear portion of its characteristic so that the combination should pass a rectified current equal to the maximum 8 load current for the valve The millivoltmeter M measures the voltage developed across a proportion of the load RL and is scaled by the appropriate range resistor RT so that the rated current through the load will deflect M to the middle of the good zone of
29. ck CH R Aj Checks insulation cathode and heater to Aj Ao Gi S CH R D Checks insulation cathode and heater to D CH R D Checks insulation cathode heater to D gt 22 Cathode to Heater insulation check 62 Turn the CIRCUIT SELECTOR Switch to C H and the ELECTRODE SELECTOR Switch to C H Any insulation breakdown which occurs between heater hot and the cathode will be directly indicated on the insulation resistance scale of the meter It is not possible to state a rejection figure in M Q for a valve under test for such a fault will be of considerable importance in some circuits whilst in a few cases its presence has virtually no consequence at all The instrument is capable of giving the insulation between cathode and heater and the acceptance or rejection of the valve can only be determined when the operator has details of the circuit in which the valve is to be used In those cases where these details are not known it is always better to reject a valve having an insulation resistance less than IOMQ It will be appreciated that there are many circuits in which an appreciable potential exists between heater and cathode dc amplifiers etc and the presence of heater to cathode insulation breakdown even of the order of many M Q can often give rise to quite serious trouble Heater to cathode insulation breakdown either permanent or intermittent can also give rise to noise in valve amplifier circuits Determination of Valve condition
30. ck for incorrect setting of the ROLLER SELECTOR Switch or electrode voltages If these are correct and the relay continues to buzz when the instrument is switched on again the valve is probably soft gassy and the test should proceed no further If upon removing the offending valve the relay continues to operate the instrument should be switched off When switched on again the instrument should function normally To check relative goodness of Valve in conjunction with Coloured Comparison Scale 70 a Using recommended anode current i Do not alter ANODE CURRENT controls but adjust NEG GRID VOLTS control until meter is balanced to zero ii Slowly rotate SET mA V control to SET ZERO position and make any final adjustment to zero using fine ANODE CURRENT control See Note 3 iii Continue rotation of SET mA V control to expected value of mA V meter needle should rise iv The comparative goodness of the valve will now be shown by the position of meter needle on coloured scale This scale is divided into three zones and all valves coming within the green portion can be regarded as satisfactory Readings in the intermediate zone between the red and green sections are not entirely satisfactory although the valve may be capable of working in some circuits at lowered efficiency whilst readings in the red zone indicate that the valve should be rejected or replaced 71 b Using recommended negative grid vol
31. entioned in the previous paragraph and they must therefore be tested in two separate sections as a pentode or triode respectively THE USE OF THE LINKS ON THE VALVE PANEL OF THE INSTRUMENT 98 These links in the A and A circuits respectively enable a load to be inserted into the anode circuit of the valve under test By removing the shorting links and inserting the appropriate resistor or other load across the terminals which it is desired to include in the circuit it is possible to obtain certain dynamic figures for the valve or electrode system under test 99 The links also enable a suitable dc Moving Coil Ammeter with low millivolt drop to be inserted in series with the anode of the valve under test Variations in the settings of the ANODE CURRENT controls will not materially affect the readings of the external meter which will read 0 5 of the actual current flowing i e the external meter reading must be multiplied by 2 for true anode current Note 6 Beware of high voltages on shorting links Checking Tuning Indicators TI 100 Tuning indicators Magic Eyes are tested with the controls set to the figures in the data table the SCREEN SWITCH being used to obtain target volts the appropriate anode load being inserted in accordance with the value shown in the remarks column 29 At the approximate bias given in the table the triode section should be at cut off and the eye fully closed Reducing the grid bias to zer
32. ever 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 maintaining the sinusoidal form of the operative negative half cycle K 7 Using the simple expression for the anode current of a triode la Ea pEg Ra and transforming this for ac operation on the positive half cycle of applied anode volts we have K 1 O T Q T la mean x J Ea sin otto Eg sin wt Ra T Wt 0 Gr 0 8 Deriving this in terms of rms applied voltages and remembering that anode current flows only on the positive half cycle and will be read on a mean reading dc meter we have K RMS l DO la mean lt Ea x uEg x 2 2Ra 1 1 Eg 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 or pentode valves which would follow the general form la f Ea pi Es u2 Ea 9 Thus with an applied rms anode and or screen voltage equal to 1 1 x Va dc and a mean value of half wave rectified bias voltage equal to 0 5x 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 the applied dc test volts This relationship holds for all practical purposes over the full c
33. from Static Characteristic Data 63 Normaliy a valve unless it is a diode or rectifier is checked by a comparison of its actual mutual conductance with the rated figure The broad procedure for obtaining this figure consists of 1 Applying to the valve the recommended electrode voltages 11 Backing off to zero the standing anode current thus produced 111 Applying a small incremental signal to the grid of the valve iv Assessing the mutual conductance and consequently the goodness of the valve from the resultant rise in anode current 64 Provision is made to test for mutual conductance under two conditions i Where the measurement is made at a predetermined fixed value of grid bias the resulting anode current being balanced out ii Where the measurement is made at the predetermined optimum value of anode current the grid bias being adjusted to give a balance 65 In either of these cases the determination of goodness can be made by a A comparison of the mutual conductance of the valve on a percentage basis with its rated figure the comparative goodness factor being indicated on a coloured good replace scale b A direct numerical determination of the valve s mutual conductance in mA V which can then be compared with the rated figure 66 In certain circumstances where for example the valve is used as an oscillator or output valve working at peak emission more useful informati
34. haracteristic 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 type of instrument as on a complete characteristic meter as it may be necessary to set the test point anywhere on the characteristic to correspond to required working conditions Further in the absence of any printed or predetermined test figure it must be possible to determine test conditions directly from manufacturers published curves or 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 grid and heater 6 voltages corresponding to the working point of the valve and backing 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 coloured scale 0 gGogpogc FIG 1 BASIC CIRCUIT FOR CHECKING OF MUTUAL CHARACTERISTICS 11 Figure 1 shows the fundamental circuit used in this measurement With the requisite electrode voltages applied to the valve the half wave anode current causes a voltage drop in the resistor RL which is sufficiently
35. hard O NO GO zl ON Un La WN l keet CN Un BW bn Item No L bouge Ara COM G A ON CA hn e Part No 40466 24 14655 2 14548 4 4650 A 10466 2 14647 2 11832 5 14648 2 14644 2 14643 2 14642 2 14646 2 20885 A 14645 2 20885 B 3658 2 ANODE CURRENT SWITCH ASSEMBLY 40464 Part No 40464 1 12049 29 12049 388 12049 389 12049 390 12049 39 12049 392 12049 393 12049 394 12049 395 12049 396 12049 397 RELAY ASSEMBLY 40466 A Description Relay Board tagged Nylock Anchor Plate ABA Contact Contact Screw Contact Armature Spring Split Pin Spring Spring Retainer Armature Pole Piece Contact Spring Wound Bobbin Armature Retainer Wound Bobbin Anchor Plate Description Anode Current Switch Resistor 800 2 Resistor 2400 2 Resistor 600Q 2 Resistor 3kQ 2 Resistor 15kQ 2 Resistor 814kQ 2 Resistor 406kQ 2 Resistor 202kQ 2 Resistor 100kQ 2 Resistor 31 5kQ 2 Resistor 4 35kQ 2 37 Circuit Ref Circuit Ref R15 R23 R24 R26 R27 R28 R29 R30 R31 R32 R33 R34 R35 Qty off Q w off bech Fe Fast Fach Jee s NO Item No Part No 40140 9 40140 4 40140 3 40140 20 40140 6 40140 7 40140 1 40140 14 40140 11 40140 10 40140 19 40140 16 40140 5 40140 8 10281 1 40140 2 10509 1 40166 3 14651 1 40157 C 20903 A 20968 1 30008 62 14714 A 14714 B 30008 63 14264 2 40506 3 14745 1
36. he same coloured meter scale L AN0DE curren T N z unes MANS SCREEN CIALUTY ELECTRODE 103 230 Yu 500 VOLTS SELECTOR SELECTOR 19 The rotary control SET mA V is of the spring return type and once a test has been made automatically returns to its start position at which point the measuring circuit is shunted to a safety condition Thus if a subsequent test is carelessly attempted with circuit wrongly set or if for instance a gassy valve is tested this will be shown up before the circuit is put in a sensitive condition for mutual conductance testing and no damage will result to the instrument 20 The final position of the CIRCUIT SELECTOR marked GAS places the meter M shunted as a microammeter in series with a resistor in the grid circuit of the valve being tested and allows the direct measurement of grid current in 4A 10 21 Further examination of the circuit diagram will show the inclusion of a safety relay with windings RL2 and RL3 in the screen and anode circuits respectively Overloads due to conditions of valve failure or misuse associated with either or both of these circuits will trip the relay This connects a high resistance lamp in series with the transformer primary windings assisted by a hold off winding RL1 at the same time making a red warning light visible through the meter scale This places the whole instrument in a safety condition Normal working cannot be restored until the instrument has been
37. hode anode 1 and grid S R Ai Checks insulation screen to filament cathode and grid 59 Study of the table set out above will show that all normally expected insulation breakdowns are covered with the exception of cathode to grid which case is covered in a later check Thus a reading on the meter of 1 M Q when the SELECTOR Switch is set to A R and the ELECTRODE SELECTOR switch is set to A can only indicate a breakdown from anode 1 to grid provided that breakdowns are not indicated in any other insulation test with heater either hot or cold It is therefore apparent that it is possible to deduce between which electrodes a breakdown is occurring although this information is normally never required for in general any appreciable inter electrode breakdown will render the valve useless Insulation checks with the valve hot 60 All the tests referred to in section 58 were carried out with the valve heater cold The CIRCUIT SELECTOR Switch should now be set to CH R and a short time allowed to elapse to enable the valve to reach working temperature With the ELECTRODE SELECTOR Switch set to A D and D in turn any deflection will denote in M the amount of insulation breakdown which occurs with cathode and heater strapped together to any other electrode 61 Table 3 sets out below the manner in which these insulation checks are made TABLE 3 Circuit Selector Electrode Selector Switch Position Switch Position Insulation Che
38. ibrated from 0 10mA the second having an inner and outer set of calibration figures Only the outer set of figures marked in steps of 10mA from 0 90mA apply when anode current is being measur d These controls enable the expected anode current from the valve under test to be set upon the instrument and also serve as a means of final adjust ment prior to making slope measurement mA V tests These controls do in effect back off the anode current passed by the valve and to prevent overloading they should be set to the expected figure before the CIRCUIT SELECTOR switch is set to the position TEST 19 52 When checking diodes and rectifiers the inner range of figures around the right hand switch become operative enabling the operator to select the required load which is normally 1mA per anode in the case of signal diodes and from 5 120mA per anode for high vacuum power rectifiers The Negative Grid Volts Control 53 This is a continuously variable control calibrated 0 40 and marked NEG GRID VOLTS which enables the initial negative bias at which a test is made to be set at any value between 0 and minus 40 volts The Set mA V Control 54 The mA V control marked 1 20mA V enables the rapid checking of the operative goodness of a valve on a replace good scale on the moving coil indicator or alternatively the direct measurement of mutual conductance in mA V 20 CHAPTER 3 OPERATING INSTRUCTIONS amp GENE
39. low resistance 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 1s shown on the dc millivoltmeter M When this difference is zero the voltage Vb is a measure of the anode current in RL la V and the control Vb is thus calibrated in mA anode current RL 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 valve in mA V is 1 volts In practice dVg the f s d of M is 130 RL millivolts and the scale is zoned in three colours green from 130 to 70 indicating a good valve white from 70 to 50 representing a failing valve and red below 50 indicative of a reject Thus the operating procedure after backing off the initial anode current is to set control dVg calibrated in mA V to a maximum of 20 to the rated mutual conductance and note the deflection on the coloured scale of M to determine valve goodness 12 This arrangement which gives an incremental grid voltage inversely proportional to slope avoids errors otherwise likely to occur on high slope valves which often exhibit marked curvature of characteristic 13 The stopper diode D3 shown in the screen supply
40. ltages are automatically correct throughout the instrument Insulation checks with the valve cold 57 1 The Valve Data Manual supplied with the instrument or the Valve Manu facturer s Data should now be consulted and the ROLLER SELECTOR Switch set up as explained in Chapter 2 Section 35 2 Set the HEATER VOLTAGE Switches to the correct value for the valve under test and insert the valve into its appropriate holder making any necessary connection to top or side caps Note Where given heater voltages in parenthesis should be employed 3 Set the CIRCUIT SELECTOR Switch to H CONT and the ELECTRODE SELECTOR Switch at C H The meter should now indicate a short thus indicating heater continuity 4 Set the CIRCUIT SELECTOR Switch at A R and S R in turn using each of these settings in conjunction with successive settings of the ELECTRODE SELECTOR Switch at A Az D and D The meter will now indicate any insulation breakdown between electrodes 58 5 Table 2 sets out the manner in which insulation checks are made 21 TABLE 2 Circuit Selector Electrode Selector Switch Position Switch Position Insulation Check A R A Checks insulation anode 1 to screen filament cathode anode 2 and grid A R A gt Checks insulation anode 2 to screen filament cathode anode 1 and grid A R D Checks insulation D to screen filament cathode anode 1 and grid A R D Checks insulation D to screen filament cat
41. mall size and constructed to comply with the requirements of the U K Govern ment Climatic Tests Specification K 114 When closed it is completely shower proof All components likely to require replacement or adjustment in service are conveniently located on sub assembly boards on the outer framework of the assembly and are immediately to hand on removing the case whilst the open framework construction used reduces weight to a minimum and ensures a maximum of accessibility Mains Supply 27 Special attention to design details has rendered an instrument suitable for operation on ac mains from 50 500 c s 10 over the following voltage ranges 105 120V 175 250V DIAGRAM OF CONNECTIONS FOR SPECIAL VALVE HOLDERS Showing pin connections viewed from above 13 CHAPTER 2 THE VALVE PANEL AND CONTROL UNIT The Valve Panel and Selector Switch 28 The Valve Panel comprises 20 Valve Holders of the following types English 4 5 pin English 7 pin English 9 pin Philips 8 pin side contact B7G B8A B8G American Loctal B9G B9A Mazda Octal International Octal B3G American 4 pin UX American 5 pin UX American 6 pin UX American small 7 pin UX American medium 7 pin UX two disc seal and a special flying lead Valve Holders See Figs 5 and 6 for diagram of standard pin connections 29 In the case of the flying lead and disc seal valves see Fig 8 the pin numbering sequence corresponding to the set up Data is printed on
42. o the eye should open fully and the value of anode current should be approximately that appearing in the table where given In the case of double sensitivity indicators giving multiple images responding to different sensitivities two sets of data where possible are given the first set referring to the more sensitive indication Checking Gas Filled Rectifiers GR 101 Gaseous rectifiers are tested in conjunction with a load resistor of suitable wattage connected across the link terminals the value of resistance being given in K Q in the remarks column This type of rectifier is not tested on the rectifier or diode test circuits but with the CIRCUIT SELECTOR set to TEST the appropriate voltage and representative anode current figures being given in the valve data columns Full wave examples of this class of valve are of course tested at the ELECTRODE SELECTOR positions A and Ag a suitable resistor being connected across each of the two anode links The maximum loading on these rectifiers must be limited to 100mA per anode to avoid damage to the instrument Checking Cold Cathode Rectifiers CCR 102 Cold cathode rectifiers designated by the symbol CCR can be tested in a similar manner the anode voltage approximate anode current and load resistance being given in the data columns COPYRIGHT No information or diagrams in whole or in part may be copied or reproduced without the prior permission in writing of Avo Limited
43. ols and the 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 20 valve bases provided accommodate valves on standard bases in common use but in addition disc seal co axial and wire ended valves can also 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 AYO Valve Data Manual whilst the letters signify the particular 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 Fault Indicator The Indicating 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 instructions are given as a preface to the AVO Valve Data Manual 2 DI The instrument will 1 2 3 4 5 6 7 8 9 10 Check heater continuity Measure insulation between electrodes with valve cold
44. on than is given by the usual mutual conductance figure can be gained from the anode current obtained for a given set of electrode voltages Such conditions are catered for by calibrating the backing off controls in terms of anode current milliamps Thus when the standing anode current has been backed off to zero as shown by the meter indication not calibrated in anode current the reading of the backing off controls gives the anode current for the valve under test at a particular combination of electrode voltages This figure can be compared with expected anode current for the conditions employed to determine the valve s suitability for the function it has to perform 23 67 It is obvious that this arrangement also enables complete valve characteristics of anode current related to electrode voltages to be plotted it merely being necessary to record the anode current obtained at a series of electrode voltage settings either anode screen or grid and plotting the mutual characteristics I aVe Ia Va etc from the data thus obtained 68 The detailed instructions for making the measurement outlined above having completed the inter electrode insulation checks are as follows 69 Set ANODE VOLTS SCREEN VOLTS NEG GRID VOLTS and ANODE CURRENT controls to the value indicated in Valve Data then set CIRCUIT SELECTOR to TEST and ELECTRODE SELECTOR to A Note 1 Should the protective relay operate switch off and che
45. rked 625 117 and 1 4 80 the second being an 18 way switch sur rounded by two sets of calibration figures The outer set of voltages on the latter can be selected when the toggle switch is in its left hand position 625 117 whilst the inner set of voltages can be selected when the toggle switch is in its right hand position 1 4 80 Table 1 gives details of the 32 available heater voltages Note Where given heater voltages in parenthesis should be employed 18 TABLE 1 OUTER RING INNER RING On load heater volts ap On load heater volts ap pearing at valve base with pearing at valve base with toggle switch set to position toggle switch set to position 625 117 1 4 80 625 1 25 1 4 2 2 5 3 4 4 5 5 5 7 6 3 7 5 10 11 12 6 13 15 16 18 20 23 25 28 30 35 40 45 48 55 70 80 117 The Anode and Screen Voltage Switches 50 These switches enable the requisite electrode voltages to be applied to screen and anodes of valves for the purpose of carrying out mutual characteristic measurements They are calibrated in the equivalent dc voltage settings and therefore no account need be taken of the actual value of ac voltage which appears at the electrodes of the valve for as already explained in Chapter 1 the actual voltage will differ from the equivalent dc value marked at the switch position The Anode Current Controls 51 This is a dual control comprising two knobs the first being continuously variable and cal
46. switched off the fault removed and the instrument switched on again The Valve Holder Panel 22 The valve holder panel by means of which the valve is connected to the test circuit comprises 20 valve bases covering all valves likely to be encountered in normal use including disc seal and wire ended valves The holders are wired with their corresponding sockets according to standard numbering in parallel 23 The wire connection loops thus formed are connected to the wiper rotors of the multi way selector switch Associated with these rotors are ten stators nine of which are each connected to an electrode test circuit the tenth one being open circuited The rotors are in the form of edge operated rollers each having the nine electrode denominations marked in symbols round their periphery the operative selection appearing in a window Thus any valve holder with pins up to nine can be set up to any electrode combination the open circuit connection serving for valves with internally connected pins 24 The problem of self oscillation that can occur with high slope valves at random high frequency due to the inter valve holder wiring has been virtually eliminated by wiring the panel in connection loops of approximately similar length and configuration so that a valve would tend to oscillate at a frequency dependent on the line thus formed These wiring loops are then closed on themselves via a connector loaded to give high loss and thus lower
47. t e b Using recommended negative grid voltage To check valves having a mutual conductance less than 1mA V Measurement of Grid Current W Checking Power Rectifiers Checking Signal Diodes Instructions for testing specific valve types Multiple Diodes and Rectifiers D DD DDD R RR Diodes and Rectifiers combined with other electrode assemblies DT DDT DP DDP DTP Double Triodes and Double Pentodes TT PP Frequency Changers H TH O TP i The use of the Links on the Valve Panel of the instrument Checking Tuning Indicators TI F W Checking Gasfilled Rectifiers GR Checking Cold Cathode Rectifiers CCR SCHEDULE OF SPARE PARTS 2 VALVE TESTER TYPE 160 SUMMARY OF DATA Purpose A simple to use double purpose Valve Tester with two functions a The rapid diagnosis of the condition of a valve 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 charac teristics or similar information using selected anode loads The instrument will check the majority of receiving valves and some small transmitting valves Description The instrument which has been constructed to conform with the 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 contr
48. t the position CH R again using the ELECTRODE SELECTOR Switch the valve is automatically checked for electrode leakage between cathode and heater strapped and all other electrodes with heater voltage applied 45 At the position C H the valve is automatically checked for cathode to heater insulation with heater voltage applied For this test the ELECTRODE SELECTOR is set to C H 46 With the CIRCUIT SELECTOR switch set to TEST and in conjunction with the ELECTRODE SELECTOR ANODE CURRENT and other relevant controls the valve is tested for its normal characteristics the majority of the information being obtained from the setting of controls the meter being used as a form of null indicator 47 At the position GAS the meter is connected in series with the control grid connection and directly indicates gas current in 4A The Electrode Selector 48 This switch used in conjunction with the CIRCUIT SELECTOR enables the meter to be associated with the anode circuit under test with the exception of test position C H This latter setting is used only in conjunction with the CIRCUIT SELECTOR set to C H for the measurement of cathode heater insulation Triodes pentodes and multiple grid valves are checked with the ELECTRODE SELECTOR set to A or A whilst diodes and rectifiers are checked at positions D and D The Heater Voltage Switches 49 Heater voltages are selected by means of two switches the first being a simple toggle switch ma
49. tage i Do not alter NEG GRID VOLTS control but adjust ANODE CURRENT controls until meter is balanced to zero ii Slowly rotate SET mA V control to SET ZERO position and make any final adjustment to zero using fine ANODE CURRENT control See Note 3 iii Continue rotation of SET mA V control to expected value of mA V meter needle should rise iv The comparative goodness of the valve will now be shown by the position of meter needle on coloured scale This scale is divided into three zones and all valves coming within the green portion can be regarded as satisfactory Readings in the intermediate zone between the red and green sections denote 24 that the valve is not entirely satisfactory although it may be capable of working in some circuits at lowered efficiency whilst readings in the red zone indicate that the valve should be rejected or replaced Note 2 Valves having a slope of less than 1mA V cannot be checked on the good replace scale and must be checked in the manner set out in paragraph 74 To check Valve by direct reading of Mutual Conductance mA V 72 a Using recommended anode current 1 Do not alter ANODE CURRENT controls but adjust NEG GRID VOLTS control until meter 1s balanced to zero ii Slowly rotate SET mA V control to SET ZERO position and make any final adjustment to zero using fine ANODE CURRENT control See Note 3 Hi Continue rotation of SET mA V control until meter needle rea
50. the Q of the line so that oscillation is virtually impossible 25 A manual is provided with a line of data for each valve likely to be encountered giving the mutual conductance and operating voltages The data given comprises the pin combinations in the order of their standard numbering and in the form in which they appear in the roller selector switch window top cap or side contact connection if any heater volts anode volts screen volts negative grid volts operating anode current and mutual conductance or load current in the case ofa rectifier Where multiple electrode assemblies are concerned test figures for each assembly are given In case a valve is en countered that does not appear in the manual the base connections and manufacturer s or other recommended test data can be directly set up on the controls without any calculation or complexity 1 vse SIATA NIOIV EE VYL EYS LOds O O O O O Pano D osa vo 989 IVLIOT NVIIVINV XN Nid YNOd NVIIYIINIY LAS Nid N3A3S TIVWS NVIIVINV O O P l O O 80W 1V 90 VOZVIA SX N Nid 3A13 NVIIVINV v9 259 Nid S b HSLLING 9XN Nid XIS NVOININVY 80 VW 1V LDO IVNOILYNYAALN OO O O OP zo os Zo re O O 8 Nid N3A3S HS LIY9g 69 Nid 3NIN HSILIYG spq fo apisaapun OAI pamata SNOILOAINNOD Nid GUVGNVILS JO WVYSVIG Generai Construction 26 The instrument is designed in suitcase form for portability and ease of stowage It is of s
51. tions an amplifying valve can 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 the problems 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 simply provided by a predetermined secondary tappings selected by calibrated switches thus minimising to a very large extent problems of size weight and cost and eliminating the necessity for separate metering 5 A slight difficulty occurs in the supply of the variable negative grid bias voltage which would normally consist of an alternating voltage of suitable 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 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 how
52. u Fa MUTUAL CONDUCTANCE CONTROL ASSEMBLY 40465 A Part No 14630 1 20969 1 14666 2 S 1512 20902 1 14660 2 14659 2 N 5 14652 1 14662 1 40465 34 12049 381 12049 382 12049 387 45482 Part No 20967 29 12049 380 12049 398 12241 12 13738 1 13819 1 13062 2 14709 A 12049 400 12049 401 12049 404 13699 1 13659 6 12049 439 12049 402 12049 384 12049 403 12049 632 13935 1 10770 9 12049 237 Description Cover Ma V Dial Dial Support Screw 4BA secures items 2 amp 3 Dial Housing Drive Bracket Drive Pin ae Hexagonal Nut SBA Nickel plated for it item 7 Switch Wafer Ge Potentiometer Resistor Board tag Resistor 70Q 1 Resistor 5009 1 Resistor 22kQ 2 Telephone Mechanism COMPONENT BOARD ASSEMBLY 20967 A Description Board tagged Resistor 2 34kQ EI Resistor 1 32MQ 1 Valve Type D77 CV140 Valve Holder B7G Valve Can ER Link Resistor 20002 a 0 5 Resistor 8kQ 5 Resistor 500Q 3 5 Capacitor 8uF electrolytic Clip for item 11 Insuloid Clip e Resistor 7000 1 Capacitor 0 04yF Resistor 330kQ 2 Capacitor 0 02uF Resistor 10kQ 2 Spindle Lock Potentiometer 5000 Resistor 10kQ 10 Circuit Ref RVI R2 R5 R14 Circuit Ref RI R3 RA V1 V2 R10 R11 R12 C3 R6 Cl R7 C2 R8 RV3 R36 Qty off Dem bech besi beet Fee beet ba LJ besch b besch p bech h beet Qty Item No
53. valve connections The socket panel is fitted with two links marked A2 and Al to which reference is made in section 98 32 Rotation of the rollers of the Selector Switch will reveal that each roller can be set in any one of ten positions the appropriate setting being indicated in the window opening at the front of the escutcheon The ten positions of each roller are marked as under 1 2 3 4 5 6 7 8 9 0 C H H G S A A Di D2 14 33 The numbers are provided in order that the switch can be rapidly set up from the code numbers given in the Valve Data Manual the corresponding electrode denominations being shown by the letter which appears in the escutcheon window immediately below the number thus Corresponds to Cathode or any other earthy electrode normally connected to cathode e g G3 Corresponds to Heater normally earthy or connected to negative 1 t in the case of a battery valve oe Corresponds to the other Heater connections or centre tap Corresponds to Control Grid Corresponds to Screen Grid or G2 Corresponds to the normal Anode of single or multiple valves In the case of an oscillator mixer valve A represents the oscillator Anode 7 Corresponds to the second Anode of double valves and in the case of oscillator mixer valves the mixer Anode 3 Corresponds to the first Diode Anode of half and full wave Signal Diode and Rectifier valves Diode and Rectifier Amplifier combinations d
54. vision for New Valve Bases 37 Although the Valve Panel caters for all valves in common use the possibility has not been overlooked that new valves and corresponding new bases may appear on the market from time to time Should such a situation arise plug in adaptors will become available commercially which will enable the new valve to be plugged into an existing socket on the Valve Panel Blank adaptors are already available to accommodate non standard bases not incorporated on the existing Valve Panel The Control Unit and its Function 38 With the exception of the Roller Selector Switch and other features incorporated on the Valve Panel all the controls are situated on the Main Panel of the instrument By the manipulation of these controls and the use of the Valve Panel the following tests can be undertaken 1 Heater continuity 2 The measurement of insulation resistance between electrodes with the valve cold 3 The measurement of insulation resistance between Heater Cathode to all other electrodes strapped together with the valve heater at operating temperature 4 The direct indication of cathode to heater insulation with the valve heater hot 5 The direct indication of valve goodness on a coloured good replace scale for a complete range of applied h t and bias voltages 6 The direct indication of anode current and mutual conductance mA V at and pre determined combination of h t and bias voltages
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