LITTON IOT CIRCUIT ASSEMBLY MANUAL

Transcription

1 LITTON IOT CIRCUIT ASSEMBLY MANUAL Date 7/18/01 REV X5 1

2 TABLE OF CONTENTS LITTON circuit assembly for I.O.T. amplifiers 1. Health and safety hazard Manual Applicability Equipment and personnel Identifying the parts Preliminary checking of the IOT a. Ion pump test b. Gas test Unpacking and rising the IOT Loading the iot in the circuit assembly frame Fitting the Body Cooling Hoses Fitting the cavities a. Fitting the primary output cavity b. Assembly of the secondary output cavity c. Fitting the electron gun leads d. Assembly of the Input cavity e. Installing Air Distribution Manifold (CH s & 56 69) f. Installing Air Distribution Manifold (CH s 45-55) g. Removing the Input cavity The complete assembly Installation of the IOT assembly into the transmitter a. Water connections b. Electrical connections Tuning the IOT a. Connectors and tuning controls of the IOT cavity assembly b. Tuning Chart c. Tuning operations Recommendations a. Recommended coolants b. Starting the transmitter at very low ambient temperatures Date 7/18/01 REV X5 2

3 1 HEALTH AND SAFETY HAZARD Date 7/18/01 REV X5 3

4 2. MANUAL APPLICABILITY LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS This manual provides information for assembling and tuning the following: LITTON circuit assembly for I.O.T. amplifiers p./n The contents of the present manual are arranged in chapters according to the following: 3. Equipment and personnel 4. Identifying the circuit assembly parts 5. Preliminary checking of the IOT 6. Unpacking and raising the IOT 7. Loading the IOT into the circuit assembly frame 8. Fitting the water pipes 9. Fitting the cavities 10. The complete assembly 11. Installation of the IOT assembly into the transmitter 12. Tuning the IOT 13. Recommendations 3. EQUIPMENT AND PERSONNEL Two people are required to install the IOT in the circuit assembly. In order to raise the IOT out of its packaging. It is recommended to have a hoist with a minimum lifting capability of 100 lbs. Other tools necessary are listed below: Allen extension ball wrench, 5mm (Provided) Allen extension ball wrench, 4mm (Provided) Screwdriver Adjustable Crescent Wrench Date 7/18/01 REV X5 4

5 4. IDENTIFYING THE PARTS LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Table 1 List of the cavity components: 1 Magnet Cart. 2 Primary output cavity. (Figure 1a) 3 Secondary output cavity (Figure 1a) 4 *Input cavity. (Figure 1a) *Note: There are two different I/P cavities required to cover channels The only difference being the size of the coupling loop. The proper loop will be installed at the factory prior to shipment. If your channel is between 14 and 64 the cavity supplied will tune over this range. If your channel designation is between channels then the tuning range of the cavity supplied will be from Air Manifold and distribution assembly (Figure 1g). 6 Tuning Crank (Figure 1b) 7 Allen screwdrivers (Figure 1b) 8 Flexible water hoses and stainless steel water fittings (including seal glands) for the cooling of the body. (Figure 9) 9 Extractor of the input cavity (Figure 37) 10 **Inter-cavity Coupling Loops used for Channels (Figure 1e) 11 **Inter-cavity Coupling Loops used for Channels (Figure 1f) 12 **Saddles for Primary Output Cavity. Used for channels 56 to 69 (Figure 1f) 13 **Secondary Cavity output Loop #16 (Figure 1c) 14 **Secondary Cavity output Loop #17 (Figure 1d) **Note: Unless otherwise specified the unit will only be shipped with the coupling loops required for the designated channel of operation. 15 Double slug tuner 16 Heater and Cathode Leads (Note: Vac-Ion Lead is supplied with IOT) Date 7/18/01 REV X5 5

6 Input and Ouput Cavities (FIG 1a) 4 & 5 mm Drivers with Tuning Crank (FIG 1b) Date 7/18/01 REV X5 6

7 Antenna Loop Assembly for Channels (FIG 1c) Antenna Loop Assembly for Channels & (FIG 1d) Date 7/18/01 REV X5 7

8 Intercavity Coupling components for Channels (FIG 1e) Note: Looking at figure 1e it is hard to tell the difference between the channel loop and the channel loop. Looking at the loops side by side one can tell the difference by examining the respective heights of the assemblies. The loop for channels is taller than the loop for channels Inter-cavity coupling components for Channels (FIG 1f) Date 7/18/01 REV X5 8

9 Air Manifold and Distribution Assembly (FIG 1g) Date 7/18/01 REV X5 9

10 5. PRELIMINARY CHECKING OF THE IOT LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS a. Ion pump test This test allows to check the vacuum in the tube and pumping away any residual gas, so a zero ion current could be indicative of an excellent vacuum (i.e. very low pressure). Typical value of the ion current is approx. 1 ua. However a zero ion current would also be registered if the IOT is at atmosphere. In this event the gas test described below should be carried out. The ion pump magnet is supplied fitted to the IOT. Connect the ion pump to the positive terminal of a high voltage d.c. power supply and the IOT heater/cathode to the negative (earth) terminal (see Fig. 2). The open circuit voltage should be in the range 3 to 4kV and the supply should have an internal impedance of 500 kohm approx. The power supply should incorporate a current metering system capable of indicating a full scale deflection of 10 ua while withstanding an overload of several milliamps. Connect a variable voltage a.c or d.c. power supply between the IOT heater and heater/cath-ode terminals. Switch on the ION pump power supply and note the current Date 7/18/01 REV X5 10

11 drawn. Typically either no current or a very small current will flow. Slowly increase the heater voltage to its rated value (do not let the heater current exceed 60A). Typically an ion current of up to 10 ua which decays rapidly will be observed. Heater and ion pump supplies should remain on until the pumping is complete, indicated by the ion current falling below 2.0_A. If this process takes more than 10 minutes it will be necessary to blow a small volume of air over the IOT gun region to prevent excessive heating. WARNING When the IOT is run in operational service, then the transmitter must incorporate a supply so that the ion pump can be run continuously. Date 7/18/01 REV X5 11

12 b. Gas test WARNING The grid must be electrically connected to the heater/cathode (HK) during this test. The gas test provides a definitive indication of the residual gas pressure in the IOT. The circuit used for the gas test is shown in Fig. 3. An electron current flows between the cathode and the IOT anode. The electrons ionize the residual gas in the IOT producing positive ions. These ions are attracted to the negatively charged drift tube walls resulting in an ion current. The magnitude of this current is a measure of the gas pressure in the IOT. Therefore, the lower the measured current, the harder the IOT s vacuum. Increase the heater voltage slowly; the heater current should at no time be allowed to exceed 60A. If, five minutes after, the heater voltage reaches 6.0 V, the positive ion current is greater than 20uA, do not run the IOT but consult the manufacturer. FIG 3 Date 7/18/01 REV X5 12

13 6. UNPACKING THE IOT LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Remove the lid of the crate, then the top cushion and the two cushions immediately below it. Now fit the two eyebolts as shown in Fig. 4. Using a suitable hoist lift the IOT out of the crate. Note that the foam packing surrounding the output ceramic of the IOT is split in two halves (see Fig. 5). Care should be taken to ensure that the foam does not jam on the inside of the crate when raising the tube (see Fig. 6). NOTE Avoid touching with hands the output ceramic of the IOT. It is advisable to wear cotton gloves. FIG 4 FIG 5 FIG 6 NOTE: The wooden crate should be retained for future repacking or storage of the IOT. To repack the IOT the procedures described in this paragraph are reversed. When repacked, for storage, the IOT should be kept vertical. The vacuum should be checked periodically (every 3 to 4 months, or in accordance with the provisions of the Warranty Leaflet enclosed with the IOT). If necessary, the tube should be pumped by means of the ion pump (refer to the previous paragraphs 5.a Ion pump test and 5.b Gas test). Date 7/18/01 REV X5 13

14 7. LOADING THE IOT IN THE CIRCUIT ASSEMBLY FRAME LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Position the cavity assembly frame directly beneath the IOT, taking care not to strike the collector against the frame. Slowly lower the IOT into the frame, one person guiding the tube through the magnet coils, until the mounting flange seats correctly in the frame (see Fig. 7). Ensure that the two body water fittings on the output drift tube are positioned appropriately for connection to the transmitter, but not towards the secondary output cavity side of the circuit. Remove the hoist and the eyebolts and retain them in a safe place (see Fig. 8) FIG 7 FIG 8 Date 7/18/01 REV X5 14

15 8. FITTING THE WATER PIPES LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS a. Fitting the body water pipes Before connecting the body cooling hose to the IOT place a minimum of 5 wraps of teflon (ptfe) plumbers tape around the threads of the connecting pipe. Then using a ¾ wrench thread the pipe into the body cooling fittings located on the IOT. (see Fig.9). Figure 9 shows the body cooling fittings oriented to face the front of the IOT Trolley Assy. FIG 9 Date 7/18/01 REV X5 15

16 9. FITTING THE CAVITIES LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS a. Fitting the primary output cavity Note: Remove the protective cover from the output ceramic window before installing the cavity. Unpack the cavities and separate the two halves of the primary output cavity; inspect all the cavity contact fingers for damage. Using two people carefully fit the primary output cavity halves around the IOT, ensuring that each is the right way up and in the correct position Note: With the front of the trolley at your left the first cavity half has to be rotated into position per figures 10a 10d. This rotational method of installation is only required when the body cooling fittings occur underneath one of the cavity halves. FIG 10a FIG 10b FIG 10c FIG 10d Date 7/18/01 REV X5 16

17 Once the two halves have been aligned begin to tighten the screws, using the 4 mm extension ball wrench provided, ensuring that the interconnection tuning rods (figure 10g) have engaged before fully tightening (see figures 10e 10h). FIG 10e FIG 10f FIG 10g FIG 10h Date 7/18/01 REV X5 17

18 b. Assembly of the secondary output cavity Attach the center conductor and inter-cavity loop assembly together for the appropriate channel per below. Pick the proper inter-cavity transition and place into the secondary cavity with the correct orientation per the following figures listed below. Note: In most cases the secondary output cavities will be shipped with the proper inter-cavity loop assembly already installed. Low Band Loop Assemblies Channel corverage: Loop # for Ch. 14 to 24 (Figures 11a and 11b) Loop # for Ch. 25 to 44 (Figures 11c and 11d) Loop # for Ch. 45 to 55 (Figures 11e and 11f) High Band Loop # for Ch. 56 to 69 (Figures 12a and 12b) Note: The smaller diameter center conductor is used with the Loop Assy. for Channels Date 7/18/01 REV X5 18

19 CH Low Band Configuration FIG 11a CH Low Band Configuration FIG 11b Date 7/18/01 REV X5 19

20 CH Low Band Configuration FIG 11c CH Low Band Configuration FIG 11d Date 7/18/01 REV X5 20

21 CH Low Band Configuration FIG 11e CH Low Band Configuration FIG 11f Date 7/18/01 REV X5 21

22 CH High Band Configuration FIG 12a CH High Band Configuration FIG 12b Date 7/18/01 REV X5 22

23 Install the transition-rotating lever (Fig. 13a and 13b). LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS FIG 13a FIG 13b Date 7/18/01 REV X5 23

24 Attach belt to the rotating lever (Fig. 14) LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Fig 14 After the belt is attached with the loop in the proper 90 deg position adjust the tuning knob position to add enough tension to the belt to prevent slipping (Fig. 15). Make sure the counter is set to read 90 degrees before tightening in place. FIG 15 Date 7/18/01 REV X5 24

25 For channels 55 to 69, install the Saddles using a 2.5 mm Allen driver, top and bottom, into the Primary Cavity (Figures 16a & 16b). FIG 16a FIG 16b Date 7/18/01 REV X5 25

26 Lift the secondary output cavity and carefully position it on the support points of the frame. Take care when guiding the coupling loop into the primary output cavity to avoid damage (Fig. 17a and 17b). Adjust the height of the support points so that the holes inside the secondary cavity are aligned with the corresponding tapped holes on the mounting flange of the primary output cavity. FIG 17a FIG 17b Date 7/18/01 REV X5 26

27 Attach the secondary output cavity using the five long 5 mm allen head bolts. Utilize the 5mm ball end driver to attach the socket head screws to the primary cavity (Fig. 18). FIG 18 Date 7/18/01 REV X5 27

28 Attach the End Cover using the 2.5 mm Phillips heads screws provided (Figures 19a and 19b) Note: The pipe clamp located on the End Cover should not be tightened until after all tuning operations are completed. FIG 19a FIG 19b Date 7/18/01 REV X5 28

29 The output loops, #16 &17, are keyed with a pin so the open end of the loops are facing away from the tube when the indicator displays 90 (Figures 20 & 21). Note: There are two output loops: Loop # 17 for Ch. 14 to19 and 56 to 69 (Ref Figure 1d) Loop # 16 for Ch. 20 to 55 (Ref Figure 1c) Installation of O/P Connector with loop # 16 (FIG 20) Date 7/18/01 REV X5 29

30 Installation of O/P Connector with loop # 17 (FIG 21) Date 7/18/01 REV X5 30

31 c. Fitting the electron gun leads LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Before assembly of the Input cavity onto the gun, the Cathode, Filament and Vac-Ion leads need to be routed through the Tree Assembly provided prior to connection to the electron gun (figure 22). Note: This tree has been designed to work in other cavity configurations. In this application there is no air cooling attached and connection points for air flow should be left open. FIG 22 Date 7/18/01 REV X5 31

32 The electron gun leads then must be assembled and fitted to the electron gun. Attach the three leads to their respective electron gun terminals as indicated below (Fig. 23). --lead with red band to the insulated filament terminal (heater); lead with the black band to the threaded metal stud (cathode terminal); ion pump connector to ion pump terminal. FIG 23 Date 7/18/01 REV X5 32

33 d. Assembly of the Input cavity LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Note: Remove the top cover and input junction box before attempting to install the cavity on the IOT. Lift the input cavity and carefully lower it onto the tube taking care not to damage any of the RF contact fingers (Fig. 24). The I/P cavity tuners should be oriented towards the front of the trolley. When the cavity has been lowered sufficiently, ensure that the clamps are correctly oriented (Fig. 25). FIG 24 Lower the cavity into position and apply careful downward pressure on the input cavity to ensure that it is correctly seated. Fasten the three hold clamps. FIG 25 Date 7/18/01 REV X5 33

34 e. Installation of the Air Distribution Manifold (Channels & 56 69). Remove the two screws securing the manifold clamp to the frame (see Fig. 26). Position the air distribution manifold as in Fig. 27; clamp it in place using the semi circular clamp and two screws. Connect the air hoses to the Input and secondary output cavities as indicated in figures FIG 26 FIG 27 FIG 28 Date 7/18/01 REV X5 34

35 FIG 29 FIG 30 Date 7/18/01 REV X5 35

36 f. Installation of the Air Distribution Manifold (Channels 45 55) LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Remove the two screws securing the manifold clamp to the frame (see Fig. 31). Position the air distribution manifold and clamp it in place using the semi circular clamp and two screws. Connect the air hoses to the Input and secondary output cavities as indicated in figures FIG 31 FIG 32 Date 7/18/01 REV X5 36

37 FIG 33 FIG 34 Date 7/18/01 REV X5 37

38 g. Removing the Input cavity LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS When the input cavity has to be removed (i.e. for replacing the IOT tube) it is necessary to use the extractor. Operate as follows: Unscrew the three hold clamps (Fig. 35); Position the extractor at the bottom of the cavity (Fig. 36) taking care that it hooks the two pins; Push downwards on the extractor until the cavity lifts up and is released from the tube. It is now possible to remove the I/P cavity. FIG 35 FIG 36 Date 7/18/01 REV X5 38

39 10. THE COMPLETE ASSEMBLY LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS FIG 37 Date 7/18/01 REV X5 39

40 11. INSTALLATION OF THE IOT ASSEMBLY INTO THE TRANSMITTER Wheel the IOT assembly into the transmitter rack and align the output coupler directly underneath the transmitter output feeder. a. Water connections Make the following water connections: Collector water in Note: Connect the collector inlet line to the fitting located at the center of the boiler assembly on the IOT. Collector water out Body water hoses b. Electrical connections Connect the transmitters wire harness to the HV Junction box. (Reference figure 38) Make the following electrical connections: FIG 38 Bolt the earth connections from the IOT input cavity and the transmitter frame to the grounding stud on the front left hand side of the IOT cart. Insert the rear of the junction box into its recess in the top of the input cavity and connect the leads to the associated sockets on the junction box (see Fig. 39a 39c). Screw the junction box and the cover plate back in place and connect the cover plate micro-switch to its socket on the IOT circuit assembly. Date 7/18/01 REV X5 40

41 FIG 39a FIG 39b Date 7/18/01 REV X5 41

42 FIG 39c Connect the magnet focus supply. (Figure 40) Connect the two output cavity arc detectors. (Figure 40) Connect the collector lead to the wing nut terminal on the base of the collector. Connect the input cable to the double slug tuner and drive amplifier Connect the air input to the distribution manifold. Date 7/18/01 REV X5 42

43 12. TUNING THE IOT LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS a. Connectors and tuning controls of the IOT cavity assembly FIG 40 Date 7/18/01 REV X5 43

44 b. Tuning Chart The tuning chart below only provides the rough counter settings and coupling loop angular positions needed for each channel with the exception of the nulling cavity settings. Following the tuning procedure outlined on page 46. Ch freq Input Cavity Input Nulling Cavity Prim O/P Cavity Sec. O/P Cavity Intra- Cavity Coupling Position Output Coupling Position Intra- Cavity Loop No. Output Loop No #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #14-24 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #25-44 # #45-55 # #45-55 # #45-55 # #45-55 # #45-55 # #45-55 #16 Date 7/18/01 REV X5 44

45 Ch freq Input Counter Input Nulling Cavity Prim Cavity Sec. Cavity LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS Intra- Cavity Coupling Position Output Coupling Position Intra- Cavity Loop No. Output Loop No #45-55 # #45-55 # #45-55 # #45-55 # #45-55 # #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #56-69 with #15 #17 #17 #17 #17 #17 #17 #17 #17 #17 #17 #17 #17 #17 #17 Date 7/18/01 REV X5 45

46 c. Tuning Procedure LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS The following tuning procedure assumes that the output of the IOT is terminated into a match of 1.5:1 or better. All tuning operations should be carried out with the vestigial sideband filter bypassed. The beam voltage and quiescent current should be set to the required values; for this purpose refer to the test report which comes with the tube. Tuning should be carried out using a white and syncs. video sweep signal or a low power CW RF sweep (If available use a network analyzer with a built in calibrated tracking generator). Typically, tuning should be carried out with a peak sync. drive power of 50W. This will ensure that the possibility of over dissipating the collector is avoided. 1. Rough tune the Input and two output cavities on the transmission channel frequency. See chart. 2. Tune the I/P nulling cavity to the counter setting specified on the chart by turning the right hand tuning crank. Note: No further tuning of this cavity is required. 3. Set the primary coupling and output coupling. Refer to the tuning chart. 4. Apply the drive, as described above, to the input of the slug tuner, which should be positioned directly before the input cavity. 5. Starting with the I/P set at the proper counter setting for the desired channel tune/peak the input cavity while looking at the output of the IOT and looking at the vision carrier level with a spectrum analyzer. 6. Adjust the setting of the double slug tuner while looking at the output of the IOT and looking at the vision carrier level with a spectrum analyzer. (Note: The best way to tune the input is by tuning for the best match. If available drive the IOT using a network analyzer with a built in calibrated tracking generator and bridge and use the reflected port of the Input coupler) 7. Fine tune the primary output cavity to produce a pass band roughly 2 MHz below vision carrier. 8. Fine tune the secondary output cavity to produce the required bandwidth. 9. Adjust the output/antenna loop coupling to flatten the observed frequency response. 10. Adjust the inter cavity coupling to trim the frequency response to the required bandwidth. 11. It may be necessary to go through steps 5 to 9. several times in order to obtain an acceptable frequency response at the output of the IOT. Date 7/18/01 REV X5 46

47 13. RECOMMENDATIONS LITTON IOT CIRCUIT ASSEMBLY FOR IOT AMPLIFIERS a. Recommended coolants When there is no danger from freezing, the coolants should be good quality demineralized water. Where outside ambient temperatures are such that there is a danger that pure water will freeze, the coolant should be a mixture of equal volumes of pure demineralized water and a commercial glycol antifreeze preparation containing appropriate corrosion inhibitors and ph buffers. The coolant flow will need to be increased by about 20% when the glycol water mixture is in use. It is recommended that the glycol coolant is discarded after being used for one winter season. The transmitter should then be operated with de-mineralized water during the summer before changing to a new glycol solution for the next winter. WARNING The long-term use of commercial grade, un buffered and uninhibited ethylene glycol will lead to corrosive damage to the transmitter cooling system and consequential damage to the IOT. Such coolants may only be used for a short time (not more than one week) in an emergency. b. Starting the transmitter at very low ambient temperatures At very low coolant temperatures, around 20 deg. C, the ability of glycol water mixtures to remove heat is severely reduced. Before powering the IOT at full beam power, the coolant should be at a temperature of at least 5 deg. C. At lower temperatures it should therefore be pre-warmed by running the IOT on idle current only or by any other means found appropriate. Even simply allowing the coolant to circulate all night during periods of very low ambient temperature may maintain the coolant temperature around 5 deg. C, due to the dissipation of the energy consumed by the circulating pump, pro-vided the cooling fan on the heat exchanger is off. Date 7/18/01 REV X5 47