The azimuth and elevation transducers monitor cage position in mils. This information is transmitted to the fire control system through cables and is used whenever the cage is moved automatically. This information is essential for accurately aiming the missiles. The azimuth transducer also contains a limit switch deck that defines to the FCS the position limits of the cage. If a transducer fails, the fire control system does not know where the cage is aimed, and the MLRS is deadlined. 27M repairers troubleshoot, repair, and adjust the transducers in a shop. The following troubleshooting procedures are those repairers are most likely to do.
Elevation Transducer Assembly
Troubleshooting procedures for the elevation transducer assembly are limited to the resolver test. To do it, you need the following tools and test equipment: audio oscillator, 1311A-9701; an azimuth position transducer breakout box, 13101680; two digital voltmeters, 8050A-01; a dual trace oscilloscope, 212 (500 kHz); a synchro angle indicator (angle position indicator), SR202; a test cable, 13103717; and a tool kit, 13032302.
The following procedures for the resolver test are taken from TM 9-1425-646-40. References cited are not necessary to complete this subcourse and have not been included.
The following instructions call for a 1311A-9701 audio oscillator as the power supply; however, you can use any power supply that can provide 11.7 to 11.9 VRMS, 1 W, 400 Hz. Monitor the power supply throughout the test and, if voltage goes out of tolerance, stop adjustments until power supply is brought back within tolerance.
If the assembly fails any part of this test or you see a distorted waveform, replace resolver/connector assembly.
To begin the resolver test, connect breakout box cable P1 to connector J1 on transducer. Connect breakout box cable J1 to the test cable, then the cable to the input terminals of angle position indicator (API). Connect wires as follows:
Connect these J1 wires to these terminals of the API.
Connect adapter cable from the 600-ohm terminal of the power supply to the breakout box power supply dual binding post. Connect digital voltmeter (DVM) test leads to the breakout box DVM dual binding post and set DVM for maximum AC voltage. Connect channel 2 of the oscilloscope to the breakout box test jack J1, pins 12 (RH-high) and 11 (RL-low). Connect channel 1 of oscilloscope to the breakout box test jack J1, pins 9 (R2-high) 13 (R4-low).
Adjust API for
The following oscilloscope adjustments are for both channels, with one noted exception: trigger (not for channel 1), pos sig, 20V/DIV, 1MS/DIV, sweep-norm, and AC input.
Set the following power supply controls: frequency central for 400 Hz and voltage control for the minimum voltage. Turn on DVM, API, and power supply. Adjust power supply to 11.7 to 11.9 VAC as measured on DVM.
While watching the oscilloscope and the API, rotate input shaft on the transducer and compare waveforms on channels 1 and 2 of the oscilloscope.
Note: Any time the waveforms are not correct in the following steps, replace resolver/connector.
Make sure the two signals are out of phase in the range of 0° to 180°. If they are, disconnect channel 1 leads from breakout box test J1, pins 9 and 13, and connect channel 1 leads to breakout box test J1, pins 7 (R1-high) and 8 (R3-low). Rotate input shaft on transducer in opposite direction from rotation you did when comparing waveforms on channels 1 and 2. Does the API angle go from 180° to 90°? Make sure the waveforms are out of phase in the range of 180° to 90°. Note: Any time the waveforms are not
Rotate input shaft through 0° to 270°, then to 180°, and verify that the waveform is out of phase between 270° and 180°. Leave input shaft at 180° as indicated on API. Disconnect oscilloscope from breakout box test jacks and turn it off.
Make sure the power supply voltage on DVM is between 11.7 and 11.9 VAC. Disconnect DVM leads from breakout box binding posts, and connect the leads so breakout box test jack J1, pins 7 (R1-high) and 8 (R3-low).
While watching the voltage reading on the DVM, rotate input shaft from 180° to 270°, then to 0°, then to 90°, and finally to near 180°. Make sure the R1-R3 voltage is not higher than 12.3 V.
Connect DVM leads to breakout box test jack J1, pins 9 (R2-high) and 13 (R4-low). While watching DVM as before, rotate input shaft from 180° to 90° to 0° to 270° to near 180°. Make sure the R2-R4 voltage is not higher than 12.3 V. Return input shaft to 0°. Note: If voltage measurements are not correct in the following, replace resolver/connector.
This completes the resolver test. Turn off test equipment and disconnect breakout box cable P1 from transducer assembly. Disconnect adapter cable from power supply, the breakout box cable J1 from API, and the DVM test leads from breakout box.
Azimuth Transducer Assembly
Troubleshooting procedures for the azimuth transducer assembly include two tests, five adjustments, and two fault isolations:
To troubleshoot and repair, repairers need the following:
An audio oscillator, 1311A-9701; an azimuth position transducer breakout box, 13103680; two digital voltmeters, 8050A-01; a dual trace oscilloscope, 212 (500 kHz); a synchro angle indicator (angle position indicator), SR 202;
a test cable, 13103717; and a tool kit, 13032302.
Gear Binding Test. Make sure the input gear can be turned smoothly and freely by hand. If the gear binds, refer to fault isolation of binding gear towards the end of this lesson.
Resolver Test
Note: This test calls for a 1311A-9701 oscillator as the power supply, but you can use any power supply that provides 11.7 to 11.9 VRMS, 1 W, 400 Hz. Monitor the power supply throughout the test and if the voltage goes out of tolerance, stop the adjustments until the power supply is within tolerance. If the assembly fails any part of this test or you see a distorted waveform, replace the resolver/connector.
To begin this test, connect breakout box cable P1 to connector J1 on transducer switch assembly, and connect cable P2 to connector J2. Connect breakout box cable J1 to the test cable, then connect the cable to the input terminals of the API.
Connect this wire to this terminal of the API.
Connect adapter cable from the 600-ohm terminal of the power supply to the breakout box power supply (P/S) dual binding post. Connect DVM test leads to the breakout box DVM dual binding post and set the DVM for maximum AC voltage.
Next, connect channel 2 of the oscilloscope to the breakout box test jacks J1, pins 12 (RH-high) and 11 (RL-low).
Connect channel 1 of oscilloscope to the breakout box test jack J1, pins 9 (R2-high) and 13 (R4-low).
Adjust API in the order given for the following: 11.8 V, TRK, LO, LOCAL, and RSLVR.
The following oscilloscope adjustments are for both channels, with one exception: trigger (except channel 1), pos signal, 20 V/DIV, 1 MS/DIV, sweep-normal, AC input.
Set the following power supply controls:
Frequency central for 400 Hz and voltage control for the minimum voltage. Turn on DVM, API, and power supply, and adjust power supply to between +11.7 and +11.9 VAC as measured on DVM. Then rotate input gear on transducer and compare waveforms on channels 1 and 2 of the oscilloscope. Make sure that the two signals are out of phase in the range of 0° to 180°. Note: Any time waveforms are not correct, replace/resolver connector.
Disconnect channel 1 leads from breakout box test jack J1, pins 9 and 13, and connect them to breakout box test jack J1, pins 7 (R1-high) and 8 (R3-low).
Rotate input gear on transducer in opposite direction from rotation when you compare waveforms on the channels. The API angle should go from 180° to 90
°. Compare waveform on channels 1 and 2.
Make sure the waveforms are out of phase in the range of 180° to 90°. Rotate input gear through 0°
to 270°, then to 180°, and make sure that the waveform is out of phase between 270° and 180° but is in phase at 180°. Leave input gear at 180°, as indicated on API.
Disconnect oscilloscope from breakout box test jacks and turn it off. Check power supply voltage on DVM for +11.7 to +11.9 VAC then disconnect DVM leads from breakout box binding posts and connect them to breakout box test jack -- J1, pins 7 (R1-high) and 8 (R3-low). Note: Any time voltage measurements are not correct, refer to fault isolation of the resolver test at the end of this lesson. While observing voltage readings on the DVM, rotate input gear from 180° to 270°. The voltage should not exceed 12.3 V.
Connect DVM leads to breakout box test jack J1, pins 9 (R2-high) and 13 (R4-low). Note: Any time voltage measurements are not correct, refer to fault isolation of resolver test.
While observing voltage reading on DVM, rotate input gear from 180° to 90°, then to 0°, then to 270°, then to near 180°. The voltage should not be more than 12.3 V. Reconnect DVM to breakout box DVM dual binding post.
Rotate input gear until API reads 0°. Use a pencil or chalk, and mark one tooth on the gear. Rotate input gear 360° (back to the mark) and make sure the API increases between 15.53° to 15.73°. Return input gear to 0°. Leave equipment connected for rotary limit switch adjustment.
Rotary Limit Switch Adjustment
CAUTION: The rotary limit switch has internal stops. Do not overtighten the adjusting screws because that might damage the switch. If you are not yet at the desired angle when you feel a marked increase in resistance, loosen lock screw on opposite side of deck and then complete adjustment. If you have to loosen the lock screw, go back to the other side of the deck and reset the adjustment on that side.
If the transducer-switch assembly passed the binding gear and resolver tests and the rotary limit switch cannot be adjusted, the switch/connector assembly is faulty.
Using No. 2 crosstip screwdriver and 10-mm socket, remove the six screws, two bolts, and eight washers that secure the cover. Remove cover and gasket. You can reuse the gasket if it isn't damaged. If it is damaged, replace it.
The rotary limit switch has three decks, each with two actuation points (during 360° switch shaft rotation, the contacts of each deck alternately open and close twice). The following procedures adjust these points to actuation. If switch deck A cannot be adjusted within the proper limits in the following procedure, replace switch/connector assembly.
Switch Deck A Adjustment
After connecting test leads to DVM, turn on DVM and set controls for the 200-ohm range.
Connect DVM test leads to breakout box test jack J2, pins 12 and 13, and rotate input gear on transducer until API reads about 0°. Verify that DVM is indicating open contacts.
Rotate input gear on transducer until you find point A2, where the switch is now actuating. Note: You have to find the existing switch actuation point so you'll know the switch starting point before you begin the adjustment.
Using a jeweler's screwdriver, loosen lockscrews B and H one turn. Then turn adjusting screw A, moving transducer input gear as required, until switch actuates at 59° as indicated on API. Tighten lockscrew H.
Rotate transducer input gear until API indicates about 70°. Rotate gear back and adjust screw A until the switch contacts open between 58.9 and 59.9° as indicated on API. Turning screw A clockwise moves the 59.4° line toward 90°.
You may have to try several times to make the adjustment. If necessary, slightly tighten lockscrew B to complete the adjustment so you won't overshoot the actuating point.
The only allowable difference is between 59.4° and 61.4° for opening and closing of contacts.
Rotate transducer input gear until API indicates about 50°. Rotate gear to increase angle to approach the 59.4° point again. Verify that, with the API angle increasing, the switch contacts close at no more than 61.4°.
Readjust screw A as necessary to open switch contacts between 58.9 to 59.9°, and close the contacts at no more than 61.4°. Tighten lockscrew B with a flat-tip screwdriver and rotate input gear on transducer back through 0°
on API to find point A1 where switch is now actuating.
Using a flat-tip screwdriver, loosen lockscrew H and turn adjusting screw G, moving input gear as required, until switch actuates at about 300°.
Rotate input gear back until API indicates about 290
°, then rotate the gear back towards 300° and adjust screw G until the switch contacts open between 300.1° and 301.1° (as indicated on the API).
Turning screw G clockwise moves the 300.6° line toward 360°.
Rotate input gear until API indicates about 310°, then rotate gear back toward 300°. Verify that the API angle decreases and switch contacts close at no
Readjust screw G as necessary to open switch contacts, between 300.1° and 301.1°, and close contacts at least 298.6°. Then tighten lockscrew H and recheck adjustment.
Switch Deck B Adjustment
If switch deck B cannot be adjusted within these limits, replace the switch/connector assembly.
Disconnect DVM test leads from breakout box test jack J2, pins 12 and 13, and connect them to test jack J2, pins 1 and 13. Rotate input gear on transducer until API reads about 0°, then verify that DVM is indicating closed contacts. Rotate input gear on transducer until point B2 is found where the switch is now actuating.
You have to find the existing switch actuation point so you will know the switch starting point before you begin the adjustment.
Using a flat-tip screwdriver, loosen lockscrews D and J one turn. Then turn adjusting screw I, moving transducer input gear as required, until the switch actuates at about 86° (as indicated on API). Tighten lockscrew D.
Rotate transducer input gear until API indicates about 75°. Rotate gear back toward the actuating point and adjust screw I until the switch contacts open, between 85.7° and 86.7° (as indicated on API).
You may have to try several times to make the adjustment. If necessary, tighten lockscrew J slightly so you will not overshoot the actuating point.
Rotate transducer input gear until API indicates about 95°. Rotate gear back and verify that, with the API angle decreasing, the switch contacts close at no less than 84.2°. You can expect a difference from between 86.2° and 84.2° for opening and closing of contacts.
Readjust screw I as necessary to open switch contacts, between 85.7° and 86.7°, and close the contacts at least 84.2°. Using flat-tip screwdriver, tighten lockscrew J. Rotate input gear on transducer back through 0° on the API to find point B1, where switch is now actuating. Loosen lockscrew D and turn adjusting screw C, moving input gear as required, until the switch actuates at about 274°.
Rotate the input gear back until API indicates about 285°. Rotate the gear toward 274° and adjust screw C until the switch contacts open between 273.3° and 274.3° (as indicated on the API). Turning screw C clockwise moves the 273.8° line toward 360°.
Next, rotate input gear until API indicates about 265°, then rotate gear back toward 274°. Make sure the API angle increases and the switch contacts close at no more than 275.8°. Readjust screw C as necessary to open switch contacts, between 273.3° and 274.3°, and close switch contacts at no more than 275.8°. Tighten lockscrew D and recheck adjustment.
Switch Deck C Adjustment
If switch deck C cannot be adjusted within the proper limits, replace the switch/connector assembly.
Disconnect DVM test leads from breakout box test jack J2, pins 1 and 13, and connect them to test jack J2, pins 1 and 2. Rotate the input gear on transducer until the API reads about 0°. Make sure the DVM indicates closed contacts. Now, rotate input gear on transducer until you find point C2, where the switch is now actuating. Note: You have to find the existing switch actuation point so you'll know the switch starting point before you begin the adjustment.
Using a flat-tip screwdriver, loosen lockscrews F and L one turn, then turn adjusting screw K, moving transducer input gear as required, until the switch actuates at about 158° as indicated on API. Tighten lockscrew F.
Rotate transducer input gear until API indicates about 148°, then rotate gear back towards the actuating point, and adjust screw K until the contacts open between 158.2° and 159.2° (as indicated on the API). about 167°. Rotate gear back and verify that, with the API angle decreasing, the switch contacts close at a minimum of 156.7°. You can expect a difference of between 158.7° and 156.7° for opening and closing contacts with this switch.
Readjust screw K as necessary to open switch contacts, between 158.2° and 159.2°, and to close the contacts at no less than 156.7°. Tighten lockscrew L, then rotate input gear on transducer back through 0° on the API to find point C1, where switch is now actuating.
Loosen lockscrew F, and turn adjusting screw E, moving input gear as required, until switch actuates at about 200°.
Rotate input gear until the API indicates about 211°.
Rotate gear toward 200°, and turn adjusting screw E until the switch contacts open, between 200.8° and 201.8° (as indicated on the API). Turning screw E clockwise moves the 201.3° line toward 270°.
Rotate input gear until the API indicates 190°, then turn gear back towards 201°. Verify that the API angle increases and the switch contacts close at a maximum of 203.3°. Readjust screw E as necessary to open switch contacts, between 200.8° and 201.8°, and close switch contacts at a maximum of 203.3°. Tightening lockscrew F and rechecking adjustment completes the adjustment of the rotary limit switch.
Turn off test equipment and disconnect breakout box cables from connectors J1 and J2 of transducer switch.
Disconnect the test leads from DVM and breakout box, adapter cable No. 3 from power supply, and breakout box cable J1 from API.
Position gasket and cover on transducer-switch housing. Then, using a No. 2 crosstip screwdriver and a 10-mm socket, install the six screws, two bolts, and eight washers. Torque screws and bolts between 0.5 to 0.8 N.m. (newton meter).
Tag assembly as ready for issue if test and adjustment was successfully completed.
Misoriented Switch Adjustment
Note: If any switch deck cannot be adjusted to proper limits, replace the switch/connector assembly.
This procedure establishes the switch closure angle required to adjust the rotary limit switch. The procedure that follows covers adjusting the switch closure angle for deck A. All other decks are done the same way. (The values for decks B and C are in parentheses.)
Rotate the transducer-switch input gear to point A2, where the switch actuates. Note the angle on the API. It should be about 59° (86° for B2 and 159°
for C2).
Rotate input gear so that the API angle goes through 0° until you find point A1, establishing the other limit of the switch closure. It should be approximately 300° (274° for B1, 201° for C1).
Using a jeweler's screwdriver, loosen lockscrews H and B for deck A (D and J for deck B, F and L for deck C).
Turn adjusting screw A for deck A (C for deck B, E for deck C) and move gear so that point A2 moves to the position shown.
Rotate the input gear until you find point A1 again. (It should have moved to a new position.) Return to point A2. Continue adjusting screw A and rotating gear until A2 is approximately in the position shown. Point A1 will also move to a new position.
Fault Isolation of Binding Gear
Using a crosstip screwdriver, remove the six screws and washers securing the front cover. Remove cover and gasket, and inspect all gears for proper mesh. Then inspect split gears for broken or disconnected springs.
Using 7/64-inch socket head key, loosen the clamp screw on gear B. Spin gear E and check for evidence of gear binding. If it binds, retighten clamp screw on gear B and examine gears A and F for broken teeth. Replace any defective gear. If gears are not defective, loosen clamp screw in gear A and spin-gear E. If there is no binding, replace bearings for gears A and B. If there is still binding, replace bearing for gears E and F. If there was no binding when you spun gear E, inspect gears B, C, and D for broken teeth. Replace any defective gears.
If gears are not defective, retighten clamp screw on gear B and loosen clamp screw on gear D, then spin gear E.
If it does not bind, replace the bearings for gear D. If it binds, replace the bearings for gear C.
Use methyl-ethyl-ketone to clean sealing compound from the cover gasket. Install cover and gasket and secure with the six screws and washers. Using crosstip screwdriver, tighten screws.
Use methyl-ethyl-ketone to clean sealing compound from the cover gasket. Install cover and gasket and secure with the six screws and washers. Using crosstip screwdriver, tighten screws.