1989/09/11 Caterpillar

AP-800, AP-1200 Asphalt Pavers

SUPPLEMENT: 10/22/90

SERVICE MAGAZINE; SEPTEMBER 11, 1989; PAGE 11; "Repair Parts And Troubleshooting Procedures For Grade And Slope Controls" for AP-800 and AP-1200 Asphalt Pavers. Step 6 of the troubleshooting procedure on Page 12 is incorrect. The 200 ohms should be 155 ± 5 ohms.

--------------- END SUPPLEMENT ---------------

The following gives parts and troubleshooting information for grade and slope controls.

Grade Control

Repair Parts For 8T8029 Grade Control

1 - 5E8637 Case

1 - 5E8642 Amplifier Module

1 - 7R0449 Deviation Meter

1 - 5E8641 Spring Assembly

1 - 5E8640 Right Hub

1 - 5E8639 Transducer

1 - 5E8638 Left Hub

1 - 7R0448 Switch

1 - 7R0446 Potentiometer

1 - 7R0447 Cap And Chain Large

1 - 7R0445 Cap And Chain Small

Facts To Aid In Troubleshooting

When preliminary investigation of a system malfunction indicates touble in the grade control, keep the following facts in mind to determine the specific malfunction.

1. The deviation meter will indicate deviations in grade whenever power is supplied to the grade control, regardless of the position of the Run/Standby switch.

2. In the RUN mode, the amplifier output is connected to the servovalve. In the STANDBY mode, the amplifier is not connected to the servovalve.

3. If the gain adjustment on the front panel is turned fully counterclockwise (for minimum gain), the position of the follower will not affect the amplifier or servovalve. The unit is effectively shut off.

Illustration 1. Typical example (slope control shown).

4. Preliminary checks should include examination of the cables and the leads for damaged or broken wires. Examine areas where shorting may occur, and check the power supply to be sure it is greater than 11 VDC.

5. A Slope/Grade switch located on the printed circuit board of the amplifier module must always be in the GRADE position.

Illustration 2.

Troubleshooting Procedure

1. With the grade control in STANDBY, check to see if the meter operates as the follower is slightly raised or lowered. Raising or lowering the follower approximately 2 mm (.08") should deflect the indicator to the red/white division on the meter when the gain potentiometer rotated fully clockwise.

2. If the meter operates correctly, check for power output at the servovalve with the Run/Standby switch in RUN position. Raising or lowering the follower should cause a voltage change to about 6 volts before the follower reaches the stop.

3. If the meter of the grade control does not operate, recheck the cables for damage or breaks. Replace cables that show damage. Cables that have been badly pinched or kinked may have shorted or broken leads.

4. Check the power supply to be sure that voltage is more than 11 VDC. If the voltage supply is adequate, check voltage at the grade control's larger connector between Pins A (-) and B (+) to be sure that cable wiring is not broken.

5. Using a 12 volt power source, unplug the large connector and check the meter by momentarily placing 12 VDC across Pins C and D on the large connector. The meter should deflect fully to one side. Reverse the polarity and the meter should deflect to the other side. Be sure the Run/Standby switch is in the RUN position. If the meter does not respond when 12 VDC is applied to Pins C and D, apply 12 VDC to Pins E and F. If the meter responds, the internal Slope/Grade switch is in the SLOPE position and should be changed. If the meter does not operate, replace the amplifier.

6. If the meter operates correctly, remove the cover and check the wiring to the transducer for continuity. Remove the plug from the socket on the transducer so that the pins are accessible. A circuit should be complete between Pins A and B, C and D, and E and F on the transducer. There should be approximately 5 ohms between A and B, and 200 ohms between C and D or E and F. The circuit should be open between Pins A and F, A and D, and D and F as well as between each pin and ground. If the transducer wiring has a short or break, the transducer should be replaced. If the transducer wiring is not broken and the grade control does not function, replace the amplifier.

Calibrating The Transducer

After installing a new transducer (as shown in Illustration 3) on the 8T8029 Grade Control, do the following steps.

Illustration 3.

1. 12 VDC power supply.

2. Flat screwdriver.

1. Connect the positive lead of the 12 volt power supply to Pin B of the 10 pin connector and the negative lead to Pin A.

2. Rotate the hub on the control until the stop screw is equally spaced between the two stop pins as shown in Illustration 4. A wedge can be used to keep the hub in place.

Illustration 4.

3. The needle on the deviation meter should be centered as shown in Illustration 1. If it is not, loosen the mounting screws and rotate the transducer until the needle is centered. Tighten the mounting screws. See Illustration 5.

Illustration 5.

Slope Control

Repair Parts For 8T8030 Slope Control

1 - 5E8945 Slope Sensor

1 - 5E8944 Cover

1 - 5E8642 Amplified Module

1 - 7R0448 Switch

1 - 7R0449 Deviation Meter

1 - 7R0446 Potentiometer

1 - 7R0447 Cap And Chain Large

1 - 7R0445 Cap And Chain Small

Facts To Aid In Troubleshooting

When preliminary investigation of a system malfunction indicates trouble in the slope control, keep the following facts in mind to determine the specific malfunction.

1. The deviation meter will indicate deviations in slope whenever power is supplied to the slope control, regardless of the position of the Run/Standby switch.

2. In the RUN mode, the amplifier output is connected to the servovalve. In the STANDBY mode, the amplifier is not connected to the servovalve.

3. If the gain adjustment on the front panel is turned fully counterclockwise (for minimum gain), the device's slope will not affect the amplifier or servovalve. The unit is effectively shut off.

4. Preliminary checks should include examination of cables and leads for damaged or broken wires. Examine areas where shorting may occur and check the power supply to be sure it is greater than 11 VDC.

5. A Slope/Grade switch located on the printed circuit board of the amplifier module must always be in the SLOPE position. See Illustration 2.

Troubleshooting Procedure

1. Check the deviation meter operation when the slope control is in the STANDBY position. Use the tow point jog switch to vary the screed position and note the indication. Then use the remote set point to vary the slope setpoint. In both situations, the deviation meter should deflect in one direction and then the other each time the conditions are reversed. If the meter does not move, turn the gain potentiometer fully clockwise and check for operation again. A setpoint change from 0.0% to 0.5% slope should deflect the meter to the red/white divisions at maximum gain.

2. Disconnect the power and output cable connector from the slope control. Check voltage at the socket end of the cable for at least 11 VDC between Pins A (-) and B (+). If voltage does not exist at this point, the cable or the voltage supply is faulty.

3. If power is available, place 12 volts across Pins E and F of the control's ten pin connector. Place the Run/Standby switch in the RUN position. The meter should deflect fully to one side. Reverse the polarity, and the meter should deflect to the other side. If the meter does not respond when 12 VDC is applied to Pins E and F, apply the same voltage across Pins C and D. If the meter then responds, the internal Slope/Grade switch is in the GRADE position and should be changed. It is the only switch on the printed circuit board of the amplifier. If the meter fails to respond, replace the amplifier.

4. If the meter operates correctly, remove the cover and check the wiring to the transducer for continuity. Remove the plug from the socket on the transducer so that the pins are accessible. A circuit should be complete between Pins A and B, C and D, and E and F on the transducer. There should be approximately 10 ohms between A and B, and 350 ohms between C and D, or E and F. The circuit should be open between Pins A and F, A and D, D and F, as well as between each pin and ground. If the transducer wiring has a short or break, the transducer should be replaced. If the transducer wiring is not broken and the slope control does not function, replace the amplifier.

NOTE: Lower performance can result if either the amplifier or the transducer is replaced in the 8T8030 Slope Control. The amplifier and transducer are calibrated together at the factory.

Matching The Amplifier And Transducer

1. 12 VDC power supply.

2. 6V7070 Multimeter or equivalent.

3. Small flat screwdriver.

4. Slope remote set point (if possible use the set point that will stay with this control).

5. A fixture that can be tilted from 0% slope to ± 6% slope.

1. Mount the control on the fixture and level the fixture from front to rear and left to right.

2. Connect the positive lead of the 12 volt power supply to Pin B of the 10 pin connector and the negative lead to Pin A.

3. Connect the leads of the multimeter to Pins E and F.

4. Plug in the remote set point and set it to 0% slope.

5. Set the gain potentiometer fully clockwise (CW).

6. Check the deviation meter. If the needle is not centered loosen the mounting clips and rotate the transducer until the needle is centered. See Illustration 6.

Illustration 6.

7. Tilt the fixture to which the control is mounted until the multimeter reading is 0.000 ± 0.010 volts.

8. Rotate the control to 6.00 ± 0.01% slope counterclockwise (CCW).

9. Turn the remote set point until it indicates 6% counterclockwise (CCW).

10. Adjust range potentiometer (P1), until the multimeter reading is at zero. See Illustration 2.

11. Rotate the control to 6.00 ± 0.01% slope clockwise (CW).

12. Turn the remote set point until it indicates 6% clockwise (CW). Note the multimeter reading.

13. Adjust range potentiometer (P1) to equalize in both amount and direction between clockwise and counterclockwise. For example, if the multimeter reading is 0.62, adjust (P1) until the reading is 1/2 of 0.62 or 0.31.

14. Adjust the control and set point to zero slope. The multimeter reading must not exceed 0.10 volts at 0% slope.

15. Adjust the control and set point to 6% counterclockwise (CCW). The multimeter reading should be within .05 volts of the final reading taken in Step 13.

NOTE: The final reading taken in Steps 13 and 15 must not exceed 1.0 volts at ± 6% slope.

16. Use an electronic grade RTV to reseal range potentiometer (P1).