Usage:
The 2P2340 Magneto Test Bench is used to make the tests of all of the magneto systems. Before making any tests, visually inspect the magneto for parts that have damage. Always make sure the drive coupling on the magneto is free to turn a minimum of 3 revolutions. A multimeter with the ability to give accuracy with an input of 30,000 ohms per volt or more is also used in these tests.
Some of the time, a magneto will operate correctly at room temperature but will have a failure when the magneto becomes hot. An oven with the ability to heat a magneto evenly to 190° to 200° F, is used for this test procedure. Always do this test before putting the magneto back in service.
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When adjusting the timing of the magneto on the test bench, always use a screw driver that has insulation on the handle. If a potentiometer has a short circuit, a voltage of 160 to 180 VDC will be on the adjustment screw. |
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To determine the source of the problem in a magneto a series of tests are made before making any repair or adjustments. These tests will give aid to the serviceman in making a quick analysis of the problem. Once the area with the defect is determined, follow the corresponding REPAIR PROCEDURE. Always complete this series of tests after making any repair or adjustments to the magneto.
A. There Is A Mechanical Problem In The Drive System
Turn the drive coupling on the magneto at least three or four complete revolutions. If the drive coupling does not turn or will not turn smoothly, disassemble the magneto and check all components for cracks, breaks or missing pieces. Make the necessary repairs as shown in the section MECHANICAL DRIVE REPAIR and do the FAILURE ANALYSIS again to be sure the magneto does not have any other problem.
B. One Cylinder Fires Too Often; 6 And 8 Cylinder Magnetos
1. With the magneto still installed in the test bench, remove screws (1) from cover (2). Move the cover to one side and check for any loose or broken wires or wires with worn or broken insulation.
NOTE: If any loose or broken wires or wires with worn or broken insulation are found, make the necessary repairs. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
2. Remove screws (3). Move the power board and heat sink assembly to one side and check the wires as in Step 1.
3. Put the heat sink and the power board section into position and install screws (3).
4. Put the selector switch of a multimeter to the 10 VDC scale. Turn the speed control knob from OFF to a point where the magneto is running at 1200 rpm. Put the negative probe of the multimeter on terminal (C-11) (distribution board terminal with white/yellow wire). Put the positive probe on terminal (C-1) (distribution board terminal with white/green wire). The generator bias is good if the voltage is between 2.15 and 4.50 VDC. Check the resistance of the pulser coil. Disconnect the pulser wires from the distribution board [terminals (C-3) through (C-8) for 6 cylinder magnetos, terminals (C-3) through (C-10) for 8 and 12 cylinder magnetos, and also terminals (E-3), (E-5), (E-10) and (E-12) for 12 cylinder magnetos].
Put the multimeter switch to the RX100 scale and connect one of the probes to any white/green wire. Check the resistance between the white/green wire and each pulser wire. If the resistance between any wire and the white/green wire is not between 600 and 800 ohms, install a new pulser coil as shown in the section PULSE COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
NOTE: If there is a reading of 0 resistance when checking a wire on magnetos with the jumper wires between the distribution board and the power board, check the jumper wires for short circuits.
If the resistance of the pulser coil is good and the generator bias is good, the distribution board has a defect. Install a new distribution board as shown in the section DISTRIBUTION BOARD INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
5. If the voltage is less than 2.15 VDC, remove the white/yellow wire from terminal (C-11). Put the negative probe on the white/yellow wire and the positive probe on terminal (C-1).
If the voltage is 2.15 to 4.90 VDC, stop the magneto. Remove screws (3) and move the power board and heat sink section to one side. Remove the protection plate for the pulser coil. Check the pulser coil for any damage. If no damage is found, remove the magneto from the test bench. Turn the drive assembly until the timing hole in the gear is in the center of the opening and the unit is in the "flux-lock" position. The front edge of the pulser rotor must be in the center of pick up (4). If the pulser rotor is not in this position disassemble the magneto and make the necessary repairs as shown in the section MECHANICAL DRIVE REPAIR. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the pulser rotor is in the correct position but the voltage is still less than 2.15 VDC, install the magneto on the test bench. Open the heat sink section and disconnect the two gray wires from terminals (B-3) and (B-4). Put the multimeter switch on the 30 VAC scale and connect the multimeter probes on the gray wires. Run the magneto at 1200 rpm.
If the voltage is between 7 and 18 VAC the power board has a defect. Install a new power board as shown in the section POWER BOARD INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is less than 7 VAC, install a new generator coil as shown in the section GENERATOR COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
B. One Cylinder Fires Too Often; 12 Cylinder Magneto
1. With the magneto still installed in the test bench, remove screws (1) from cover (2). Move the cover to one side and check for any loose or broken wires or wires with worn or broken insulation.
NOTE: If any loose or broken wires or wires with worn or broken insulation are found, make the necessary repairs. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
2. Remove screws (3). Move the power board and heat sink assembly to one side and check the wires as in Step 1.
3. Put the heat sink and the power board section into position and install screws (3).
4. Turn the speed control knob until the magneto is running at 1200 rpm. Put the selector switch of the multimeter to the 3 VDC scale. Put the negative probe on terminal (E-1) and the positive probe on terminal (E-7). If the voltage is between 1.75 and 2.50 VDC, the generator bias is good but the distribution board that controls the cylinder that fires too often has a defect. Install a new distribution board or auxillary distribution board as shown in the corresponding INSTALLATION section.
If the voltage is less than 1.75 VDC, stop the magneto and remove the white/orange wire from terminal (E-1). Connect the negative probe of the multimeter to the white/orange wire and the positive probe to terminal (E-7). Turn the speed control knob until the magneto is running at 1200 rpm.
If the voltage is now more than 2.15 VDC, the auxillary distribution board has a defect. Install a new auxillary distribution board as shown in the corresponding INSTALLATION section. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is less than 2.15 VDC, stop the magneto and remove all of the wires from terminal block (E) and remove the auxillary distribution board.
NOTE: Put the wires in a position so they will not contact each other or the frame.
Put the negative probe of the multimeter on terminal (C-11) (terminal with white/yellow wire). Put the multimeter switch to the 10 VDC scale. Run the magneto at 1200 rpm and connect the positive probe of the multimeter on terminal (C-1) (terminal with white/green wire).
If the voltage is 2.15 to 4.50 VDC, the generator bias is good but the distribution board has a defect. Install a new distribution board as shown in the section. DISTRIBUTION BOARD INSTALLATION.
If the voltage is less than 2.15 VDC, stop the magneto and remove the white/yellow wire from terminal (C-11). Check the voltage between the white/yellow wire and terminal (C-1) with the magneto running at 1200 rpm.
If the voltage is 2.50 to 4.90 VDC, stop the magneto. Remove screws (3) and move the power board and heat sink section to one side. Remove the protection plate for the pulser coil. Check the pulser coil for any damage. If no damage is found, remove the magneto from the test bench. Turn the drive assembly until the timing hole in the gear is in the center of the opening and the unit is in the "flux-lock" position. The front edge of the pulser rotor must be in the center of pick up (4). If the pulser rotor is not in this position disassemble the magneto and make the necessary repairs as shown in the section MECHANICAL DRIVE REPAIR. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the pulser rotor is in the correct position but the voltage is still less than 2.15 VDC, install the magneto on the test bench. Open the heat sink section and disconnect the two gray wires from terminals (B-3) and (B-4). Put the multimeter switch on the 30 VAC scale and connect the multimeter probes on the gray wires. Run the magneto at 1200 rpm.
If the voltage is between 7 and 18 VAC the power board has a defect. Install a new power board as shown in the section POWER BOARD INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is less than 7 VAC, install a new generator coil as shown in the section GENERATOR COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
C. One Cylinder Does Not Fire At Regular Intervals Or One Cylinder Does Not Fire At All; 6 And 8 Cylinder Magnetos
1. With the magneto still installed in the test bench, remove screws (1) from cover (2). Move the cover to one side and check for any loose or broken wires or wires with worn or broken insulation. Each cylinder has a different color wire in the magneto. Check the wires for the cylinder that does not fire correctly.
NOTE: If any loose or broken wires or wires with worn or broken insulation are found, make the necessary repairs. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
2. Remove screws (3). Move the power board and heat sink assembly to one side and check the wires as in Step 1.
3. Terminal block (C) and the pulser coil are connected with wires. Terminals (C-3) through (C-8) are for cylinders 1 through 6 respectively for 6 cylinder magnetos. Terminals (C-3) through (C-10) are for cylinders 1 through 8 respectively for the 8 cylinder magnetos.
4. Remove the wire for the cylinder that has the defect from terminal block (C). Remove another cylinder wire from terminal block (C) that is known to be operating correctly. Install the good cylinder wire on the cylinder terminal that has the defect. Run the magneto at 1200 rpm.
If the cylinder with the defect now operates, stop the magneto. Put the multimeter switch to the RX1 scale and check the resistance from terminal (C-1) to the wire with the defect.
NOTE: The cylinder with the defect will fire in position of the good cylinder. EXAMPLE: If the wire of cylinder number 5 were put on the terminal for cylinder number 9, the number 5 light or spark will be seen in the number 9 position.
If the resistance is zero (0) the pulser coil has a short circuit. If the resistance is maximum or near maximum the pulser coil has an open circuit.
In both cases, the pulser coil has a defect. Install a new pulser coil as shown in the section PULSER COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the cylinder still does not operate correctly after changing the pulser wires, the distribution board has a defect. Install a new distribution board as shown in the section DISTRIBUTION BOARD INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
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Do not operate the magneto with a new distribution board until all of the wires from the pulser coil are checked. Check each wire for worn insulation or short circuits. A new distribution board could be destroyed if the magneto is operated with wires that are in contact with each other or the frame. |
Check the timing of the magneto and change if necessary. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
C. One Cylinder Does Not Fire At Regular Intervals Or One Cylinder Does Not Fire At All; 12 Cylinder Magneto
1. With the magneto still installed in the test bench, remove screws (1) from cover (2). Move the cover to one side and check for any loose or broken wires or wires with worn or broken insulation. Each cylinder has a different color wire in the magneto. Check the wires for the cylinder that does not fire correctly.
NOTE: If any loose or broken wires or wires with worn or broken insulation are found, make the necessary repairs. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
2. Remove screws (3). Move the power board and heat sink assembly to one side and check the wires as in Step 1.
Terminal block (E) on the auxillary distribution board and terminal block (C) on the distribution board are connected with wires to the pulser coil. Terminals (C-3) through (C-10) are for cylinders 1 through 8 respectively and terminals (E-3), (E-5), (E-10) and (E-12) are for cylinders 9, 10, 11 and 12 respectively.
If cylinder 9, 10, 11 or 12 has the defect, remove the wire of the cylinder with the defect from terminal block (E). Remove another cylinder wire from terminal block (E) that is known to be operating correctly and connect this wire to the cylinder terminal that has the defect. Run the magneto at 1200 rpm.
If the cylinder with the defect now operates, stop the magneto. Install a new pulser coil as shown in the section PULSER COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
NOTE: The cylinder with the defect will fire in the position of the good cylinder. EXAMPLE: If the wire of cylinder 9 was connected to the terminal of cylinder 11, the number 9 light or spark will be seen in place of the number 11 light or spark.
If the cylinder still does not operate correctly after changing the pulser wires, the auxillary distribution board has a defect. Install a new auxillary distribution board as shown in the corresponding INSTALLATION section. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
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Do not operate the magneto with a new auxillary distribution board until all wires from the pulser coil are checked. Check each wire for worn insulation or short circuits. A new auxillary distribution board or distribution board could be destroyed if the magneto is operated with wires that have short circuits. |
If cylinder 1, 2, 3, 4, 5, 6, 7 or 8 has a defect, remove the auxillary distribution board and put the loose wires from terminal block (E) in a position so they will not contact each other or the frame. Remove the wire for the cylinder that has the defect from terminal block (C). Remove another cylinder wire from terminal block (C) that is known to be operating correctly. Install the good cylinder wire on the cylinder terminal that has the defect. Run the magneto at 1200 rpm.
If the cylinder with the defect now operates, stop the magneto. The pulser coil has a defect. Install a new pulser coil as shown in the section PULSER COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
NOTE: The cylinder with the defect will fire in position of the good cylinder. EXAMPLE: If the wire of cylinder number 5 were put on the terminal for cylinder number 9, the number 5 light or spark will be seen in the number 9 position.
If the cylinder still does not operate correctly, the distribution board has a defect. Install a new distribution board as shown in the corresponding INSTALLATION section. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
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Do not operate the magneto with a new distribution board until all of the wires from the pulser coil are checked. Check each wire for worn insulation or short circuits. A new distribution board could be destroyed if the magneto is operated with wires that are in contact with each other or the frame. |
Check the timing of the magneto and change if necessary. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
D. One Side Of The Magneto Does Not Fire At Regular Intervals Or Does Not Fire At All
The source of this type of problem is in the power board. Install a new power board, check the timing and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
E. The Magneto Makes A Weak Spark
With the magneto still installed in the test bench, remove screws (1) from cover (2). Move the cover to one side and check for any loose or broken wires or wires with worn or broken insulation. Connect a 3N4104 capacitor to the capacitor in the end cap. Run the magneto at 1200 rpm.
If the magneto now sends a strong spark and the spark can go across a gap of more than .75 in. (17.0 mm), stop the magneto. Remove the storage capacitor and install a new capacitor as shown in the section STORAGE CAPACITOR INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the magneto still makes a weak spark, stop the magneto and remove the 3N4104 capacitor used for testing. Put the selector switch of the multimeter to the 300 VDC scale. Put the negative probe of the multimeter into pin (H) of the output plug and the positive probe into pin (G). Run the magneto at 1200 rpm and read the voltage on the multimeter.
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Use extra care when making these tests, the voltages may become as high as 1000 VAC. |
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If the voltage is less than 130 VDC, open the heat sink section of the magneto. Disconnect the white wire from terminal (B-1) (this is a wire from the generator coil). Put the multimeter switch on the 300 VAC scale and run the magneto at 1200 rpm. Put one of the multimeter probes on the disconnected wire and the other probe on terminal (B-2).
If the voltage is not between 200 and 300 VAC install a new generator coil as shown in the section GENERATOR COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is between 200 and 300 VAC, the generator coil is good. Stop the magneto and connect the white wire back to terminal (B-1). Disconnect the red wire from terminal (B-8) (this is the wire from the zener diode). Connect a 3N4103 zener diode to the system (red wire to terminal (B-8) and the black wire to the magneto frame).
Put the multimeter switch to the 300 VDC scale. Put the negative probe into pin (H) (or any white/green wire) and the positive probe into pin (G) (or the frame). Slowly make an increase in speed until the magneto is running at 1200 rpm.
If the voltage is not between 130 and 185 VDC, the zener diode has a defect. Remove the 3N4103 zener diode used for testing and install a new zener diode as shown in the section ZENER DIODE INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is more than 185 VDC the zener diode is open and must be changed. Remove the test zener diode and install a new zener diode as shown in the section ZENER DIODE INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
NOTE: If the magneto does not operate correctly with a new zener diode, the problem may be a power SCR on the distribution board. A power SCR can be destroyed if the magneto is operated for very long with an open zener diode. Install a new distribution board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the power generator, storage capacitor and power zener diode are all found to be good, the problem is in the power board. Install a new power board as shown in the section POWER BOARD INSTALLATION. Check the timing of the unit and change if necessary. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
F. The Magneto Makes No Spark
1. With the magneto still installed in the test bench, disconnect the wiring harness at the magneto. Slowly turn the speed control knob until the magneto is running at 200 rpm. Put the selector switch of the multimeter to the 300 VDC scale and put the negative probe of the multimeter into pin (H) of the output plug on the magneto. Put the positive probe into pin (G) (or on the frame) and read the voltage on the meter.
If the voltage is more than 185 VDC the zener diode is open and must be replaced. Remove the 3N4103 zener diode, and install a new zener diode as shown in the section ZENER DIODE INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
NOTE: If the magneto does not operate correctely with a new zener diode, the problem may be a power SCR on the distribution board.
A power SCR can be destroyed if the magneto is operated faster than 100 rpm with an open zener diode. Install a new distribution board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is less than 100 VDC stop the magneto and remove screws (1) from cover (2). Move the cover to one side and check the white/green wire for any breaks or worn or missing insulation.
NOTE: On magnetos for 12 cylinder engines, remove the screws that hold the auxillary distribution board to check the wiring on both distribution boards.
If any loose wires, broken wires or wires with worn or broken insulation are found, make the necessary repairs. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the wiring is good but the voltage is still less than 100 VDC open the heat sink section and disconnect the red wire from terminal (B-8) (this is the wire from the zener diode). Connect a 3N4103 zener diode to the system (red wire to terminal (B-8) and the black wire to the magneto frame).
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Never operate the magneto faster than 100 rpm with the zener diode disconnected. This would destroy the silicon controlled rectifiers on the distribution boards. |
Put the multimeter switch to the 300 VDC scale. Put the negative probe into pin (H) (or any white/green wire) and the positive probe into pin (G) (or on the frame). Slowly make an increase in speed until the magneto is running at 1200 rpm.
If the voltage is now between 130 and 185 VDC, the zener diode has a defect. Remove the test zener diode and install a new zener diode as shown in the section ZENER DIODE INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the zener diode is good, check the generator coil.
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Use extra care when making these tests, the voltages may become as high as 1000 VAC. |
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If the voltage is less than 130 VDC, open the heat sink section of the magneto. Disconnect the white wire from terminal (B-1) (this is a wire from the generator coil). Put the multimeter switch on the 300 VAC scale and run the magneto at 1200 rpm.
Put one of the multimeter probes on the disconnected wire and the other probe on terminal (B-2).
If the voltage is not between 200 and 300 VAC install a new generator coil as shown in the section GENERATOR COIL INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the generator coil is good, stop the magneto and remove the red wire from terminal (B-8) (this is the wire from the power resistor). Put the multimeter switch on the RX1 scale and make adjustments to the meter until it shows zero resistance with the probes connected to each other. Connect one probe of the multimeter to the red wire and the other probe to terminal (B-7).
The resistance must be between 8 and 12 ohms. Install a new power resistor as shown in the section POWER RESISTOR INSTALLATION if the resistance is not between 8 and 12 ohms. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the power resistor is good, test the storage capacitor. Connect a 3N4104 capacitor to the capacitor in the end cap. Run the magneto at 1200 rpm.
If the magneto now sends a strong spark and the spark can go across a gap of more than .75 in. (18 mm), stop the magneto. Remove the capacitor used for testing and install a new storage capacitor as shown in the section STORAGE CAPACITOR INSTALLATION. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the zener diode, generator coil, power resistor and the storage capacitor are all good, the power board has a defect and a new power board must be installed.
Do the FAILURE ANALYSIS again to be sure that all problems have been corrected.
If the voltage between pin (G) and pin (H) is between 130 and 185 VDC, make an increase to the speed of the magneto until it is running at 1000 rpm.
A voltage reading above 185 VDC is an indication of an open zener diode. Install a new zener diode as shown in the section ZENER DIODE INSTALLATION. Do the failure analysis again to be sure the problem has been corrected.
NOTE: If the magneto does not operate correctly with a new zener diode, the problem may be a power SCR on the distribution board. A power SCR can be destroyed if the magneto is operated faster than 100 rpm with an open zener diode. Install a new distribution board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
2. For 6 and 8 cylinder magnetos, put the multimeter switch on the 30 VDC scale and run the magneto at 30 rpm. Put the positive probe on terminal (C-2) and the negative probe on terminal (C-1). The voltage must be between 17 and 24 VDC. If the voltage is less than 11 VDC, stop the magneto and disconnect the white/red wire from terminal (C-2). Check the voltage between terminal (C-1) and the white/red wire with the magneto running at 30 rpm. If the voltage is now between 17 and 24 VDC, a trigger SCR or a potentiometer on the distribution board has a defect. Install a new distribution board.
If the voltage is still less than 17 VDC, stop the magneto, disconnect the white/green wire from terminal (C-1). Check the voltage between the white/green wire and the magneto ground with the magneto running at 30 rpm. The power board has a defect if the voltage between the white/green wire and ground is at least 25 VDC. Install a new power board and do the FAILURE ANALYSIS again.
3. For 12 cylinder magnetos, put the multimeter switch on the 30 VDC scale and run the magneto at 30 rpm. Put positive probe on terminal (E-2) and the negative probe on terminal (E-7). The voltage must be between 17 and 24 VDC. If the voltage is less than 17 VDC, stop the magneto and disconnect the white/red wire from terminal (E-2). Check the voltage between terminal (E-7) and the white/red wire with the magneto running at 30 rpm. If the voltage is now between 17 and 24 VDC, there is a defect on the auxillary distribution board. Install a new auxillary distribution board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is still less than 17 VDC, the auxillary distribution board is probably good and the main distribution board must be checked. Stop the magneto and move the auxillary distribution board to one side using care to be sure the spacer posts do not cause a short circuit on the bottom of the auxillary board. Disconnect the white/red wires from terminal (C-2). Check the voltage between the white/red wires and terminal (C-1) with the magneto running at 30 rpm.
If the voltage is now between 17 and 24 VDC, a trigger SCR or a potentiometer on the distribution board has a defect. Install a new distribution board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the voltage is still less than 17 VDC, stop the magneto and disconnect the white/green wire from terminal (C-1). Check the voltage between the white/green wire and the magneto ground with the magneto running at 30 rpm. If the voltage is at least 25 VDC, the power board has a defect. Install a new power board and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
4. For 6 and 8 cylinder magnetos, put the negative probe of the multimeter on terminal (C-11). Put the multimeter switch to the 10 VDC scale and put the positive probe on terminal (C-1). Turn the speed control knob until the magneto is running at 1200 rpm.
If the voltage is between 2.15 and 4.5 VDC, the magneto bias is good. (Go on to step 6.)
If the voltage is less than 2.15 VDC, stop the magneto and remove the white/yellow wire from terminal (C-11). Put the negative probe on the white/yellow wire and the positive probe on terminal (C-1). Turn the speed control knob until the magneto is running at 1200 rpm.
If the voltage is between 2.50 and 4.9 VDC stop the magneto, remove the protection plate for the pulser coil and inspect the pulser coil.
(When the magneto is in the "flux-lock" position the straight edge of the pulser rotor must be in the center of a pick up (4) on the pulser coil.) If the straight edge of the pulser rotor is not in alignment with the center of a pick up, loosen the retainer nut and make adjustments to the position of the rotor. Check the timing and change if necessary. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
Open the heat sink section and disconnect the gray wires from terminals (B-3) and (B-4). Put the multimeter switch to the 30 VAC scale. Check the output voltage of the bias generator by connecting the multimeter probes to the gray wires with the magneto running at 1200 rpm.
If the voltage is less than 7 VAC, install a new generator coil. Do the failure analysis again to be sure the problem has been corrected. If the voltage is between 7 and 18 VAC, the generator bias is good and the defect is in the power board. Install a new power board, assemble the magneto and do the FAILURE ANALYSIS again to be sure the problem has been corrected.
5. For 12 cylinder magnetos, put the negative probe of the multimeter on terminal (E-1) (terminal on the auxillary distribution board with the white/orange wire). Put the multimeter switch on the 3 VDC scale and put the positive probe on terminal (E-7). Turn the speed control knob until the magneto is running at 1200 rpm.
If the voltage is between 1.75 and 2.50 VDC the magneto bias is good (Go on to step 6.)
If the voltage is less than 1.75 VDC, stop the magneto and remove the white/orange wire from terminal (E-1) and check the voltage between the white/orange wire and any white/green wire with the magneto running at 1200 rpm.
If the voltage now is more than 2.15 VDC, stop the magneto and install a new auxillary distribution board.
If the voltage now is less that 2.15 VDC, disconnect the wires from terminal block (E). Make sure none of the wires are in contact with each other or the frame. Test the magneto as shown in Step 4 for 6 and 8 cylinder magnetos.
6. Put the multimeter switch to the 250 or 300 VDC scale. Disconnect the wiring harness at the transformer load bank and run the magneto at 200 rpm. Check the voltage between any white/green wire and the magneto ground. The voltage should be between 110 and 185 VDC. Make a note of the voltage. Connect the wiring harness back to the load bank and check the voltage again. If there is a difference of more than 50 VDC between the two readings, install a new distribution board. Check the timing and assemble the magneto. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
G. The Timing System Has A Defect
If the timing of any one cylinder is not correct, install the magneto in the test bench as shown in SPECIAL INSTRUCTION FORM GEG02059.
Remove the four screws holding the end cap to the magneto. With all of the wiring still connected move the end cap to one side. The potentiometers on the distribution boards for 6 and 8 cylinder magnetos are numbered in sequence from left to right (1 through 6 and 1 through 8). The 12 cylinder magnetos have an auxillary distribution board in front of the main distribution board. The four potentiometers on the auxillary distribution board are numbered in sequence left to right (9 through 12). The main distribution board is the same as the 8 cylinder board.
To make an adjustment to any one cylinder, turn the screw of the potentiometer for that cylinder.
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If a potentiometer has an internal short circuit, a 160 VDC shock may result if care is not used when making adjustments to the timing. Connect a neon tester between the adjustment screw and the magneto ground. If the tester glows, the potentiometer has a short circuit. |
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NOTE: If the adjustment screw is loose or if the timing does not change when the screw is turned, the potentiometer has a defect. Install a new distribution board or a new auxillary distribution board and test the timing of the magneto again.
If the timing of all of the cylinders is not correct (the timing of all cylinders is off the same amount), check to be sure the pulser rotor assembly is tight on the shaft. If the nut is loose on the shaft, remove the nut and install a new self-locking nut. Tighten the nut to a torque of 12 ± 1 lb. ft. (1.6 ± 0.1 mkg). Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
If the nut is tight on the shaft but timing is still not correct, check the bias generator as shown in REPAIR PROCEDURE B. If the generator bias is correct, disassemble the magneto and check:
1. Condition of the retainer key for the drive coupling, (make a repair to the shaft and install a new key).
2. The position of the arrow on the timing gear in relation to the drilled hole in the drive gear, (the arrow should point at the hole).
3. The fiber gear, (if the shaft is able to rotate with the gear held stationary, the gear must be removed and a new gear installed).
4. Do the FAILURE ANALYSIS again to be sure the problem has been corrected.
H. Magneto Does Not Operate Correctly When Hot
An electric oven is used in this part of the test. The oven must be heated to a temperature of 195° ± 5° F (90 ± 3° C) for at least one hour before the test is started.
Put the magneto in the oven. After a period of four hours remove the magneto using gloves and rags. Install the magneto in the test bench and do the FAILURE ANALYSIS tests.
NOTE: The magneto should be located in the oven so the magneto is heated evenly.
1. If there is a problem now, test and adjust the magneto as shown in REPAIR PROCEDURES A through G.
2. If there is no problem, run the magneto for two hours. Check the magneto several times during this test and make adjustments if necessary as shown in sections A through G.
3. After the magneto has run for two hours stop the magneto and let the magneto become cool or at room temperature [80° F (26° C)]. Run the magneto for one half hour and do the FAILURE ANALYSIS again.
4. If there is no problem, do Steps 1, 2 and 3 again. If there is no problem after doing Steps 1, 2 and 3 again, the magneto is ready for use.