Usage:
- I. General Troubleshooting and Repair of The Engine Horsepower Meter and Accessories
- II. Electronic Troubleshooting and Repair of The Engine Horsepower Meter
For information on how to use the Engine Horsepower Meter, see Special Instruction Form GEG02402, "Using The 5P2160 Engine Horsepower Meter Arrangement". For information on correction factors and reference material to be used with the Engine Horsepower Meter, see Special Instruction Form SEHS6947, "Reference Material and Correction Factors For Use With The 5P2160 Engine Horsepower Meter Arrangement".
General Troubleshooting And Repair Of The Engine Horsepower Meter And Accessories
General Troubleshooting Procedure
The following section gives a general procedure for isolating a faulty portion of the entire Engine Horsepower Meter Arrangement. It is written to enable a person with reasonable knowledge of electricity and a multimeter to find simple faults which are field repairable, without taking the unit to an electronics repair facility or returning it to the manufacturer.
If the following procedure does not isolate the problem, U.S. dealers should return the unit (Horsepower Meter or flowmeter only) to the appropriate address shown on page 49. Dealers outside the U.S. may wish to have the unit further inspected and repaired locally by a qualified electronics shop which is familiar with digital circuitry.
The material on pages 20-23 and pages 26-48 is intended only for those situations where it is not practical to return the unit to the U.S. for repair. U.S. dealers are urged to send their units to Fluidyne Instrumentation where repairs and calibration can be performed more precisely and efficiently.
NOTE: Be sure to check out the components by using the following procedure in the order indicated. Do not omit any tests unless the unit is known to operate correctly in that specific mode.
| NOTICE |
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Do not use a continuity light to trace circuits on either printed circuit board. Some semiconductor components can be damaged if 3 volts is connected across them. |
1. Turn the POWER switch to ON (Be sure the knob has not slipped on the shaft).
2. Do any of the display lights light?
a) YES - Go to Step 3.
b) NO - Open the Horsepower Meter and perform the steps shown on page 6. If the problem cannot be identified as a blown fuse, bad switch contact, broken wire, loose battery connection, dead batteries, etc., return the unit to Fluidyne Instrumentation (see page 49). If the problem is known to be in the power board, return only the power board to Fluidyne.
3. Are the display lights dim?
a) NO - Go to Step 4.
b) YES - Check for a voltage at the batteries of greater than 5.2 volts. If the voltage is less, recharge the batteries to over 6 volts and recheck. (If the batteries won't charge, go to Step 15.) Check for voltage losses between the batteries and wiring point 16 and the displays. The voltage should be greater than 5 volts at wiring point 16.
4. Do any of the lights have the correct brilliance?
a) YES - Go to Step 5.
b) NO - Review Step 2. If the problem cannot be found, return the unit to Fluidyne.
5. If all digits light correctly, go to Step 6. Individual lamps or related 7447's (integrated circuits) may fail while most digits work properly. Interchange known good components with suspected components. See page 24. Be sure to remove the plug-in lights carefully so they separate correctly from their sockets. Replacement lamps and 7447's are available from Fluidyne. If any soldered component is suspected, return the entire unit to Fluidyne.
6. With the POWER switch ON, turn the MODE switch to the BATT. TEST position (be sure the knob has not slipped on the shaft). Is the displayed value greater than 5.0 volts?
a) YES - The power supply circuit and displays are basically operational. Go to Step 7.
b) NO - Review Step 2. If the problem cannot be found, return the unit to Fluidyne.
7. If the BATT. TEST value is less than 5.80 volts, recharge the batteries so there is sufficient power to complete the remaining tests. If the batteries cannot be charged, Step 15.
8. Turn the MODE switch to the ENGINE SPEED VERIFY position. Is 6000 rpm displayed?
a) YES - The tachometer circuit in the Horsepower Meter is operational. Go to Step 9.
b) NO - Is only one digit wrong?
(1) YES - See step 5.
(2) NO - Check for broken wires, a broken switch, etc. If no physical defects can be seen, an oscilliscope is needed for more testing. Return the unit to Fluidyne.
NOTE: A tachometer circuit defect will not affect the flow rate readings or horsepower tests.
9. Connect the Tachometer Generator and RPM cable to the Horsepower Meter. Turn the MODE switch to any position except ENGINE SPEED VERIFY. Spin the generator shaft by hand. Is a fluctuating reading displayed (approximately 300 - 500 rpm)?
a) YES - All tachometer components are basically operational. If difficulty is encountered while running on an engine, check the tachometer generator and adjustment (see the NOTE below and page 8). Be sure to install the generator only finger-tight and check that the tachometer drive ratio is correct (shaft running at 1/2 engine speed). Electrical noise (from older electric sets) can be eliminated by using a shielded 9S3048 Cable Assembly between the tachometer generator and the 5P2159 Cable. If the tachometer circuit is correct while running an engine, go to Step 10.
b) NO - Check the rpm cable for continuity and for shorts, and the tachometer generator (see page 13). If the generator and cable check is satisfactory, look for obvious physical defects in the readout box. If none can be seen, return the unit to Fluidyne.
NOTE: Pin A of the threaded connector of the rpm cable should be connected to the center terminal of the phone jack on the opposite end. Some cables may be assembled wrong.
10. Turn the MODE switch to the GAL/HR CALIB. position. If the unit has been turned on for at least 5 minutes, is the GAL/HR CALIB. value (top display) stable and within the tolerance given on the lid of the unit?
a) YES - The gallons per hour circuitry is basically operational. Go to Step 11.
b) NO - If the value is within ± 1.0 gph, the unit may simply need to be calibrated. See pages 9 - 12.
NOTE: Special electronic equipment is needed for calibration (see page 11), so it is suggested that the unit be returned to Fluidyne for correct calibration. It is also possible that the Digital-to-Analog Converter (DAC) is malfunctioning. Replacement of this item should be done by Fluidyne.
If the GAL/HR CALIB. value is wrong, refer to Step 5; then check the power supply voltages as shown on page 6. If the GAL/HR CALIB. value is still incorrect, or the top display stays "locked up" in the first four positions of the MODE switch, the unit probably has an internal component failure. The unit should be returned to Fluidyne for repair and recalibration.
11. To check the flowmeter input circuit, connect a 1.5 volt battery across the FLOWMETER connector (+1.5 volts to pin B and ground to pin A). In the GAL/HR position (third position), is the gallons per hour reading approximately 48 gph (gph = voltage × 32.0)?
a) YES - The GAL/HR circuitry is operational. Go to Step 12.
b) NO - If Step 10 checked correctly, the problem is an open circuit between the FLOWMETER connector and wiring point C (refer to the schematic on pages 35-38). If a physical defect cannot be seen in the wiring or switch, return the unit to Fluidyne.
12. Perform all of Step 2 on page 16. Do not perform Step 3 (page 16) unless Step 11 above was correct, but the flow rates are erratic or wrong when the flowmeter is connected to the engine. Did the flowmeter pass the checks shown on page 16?
a) YES - The flowmeter is basically functional. Go to Step 13.
b) NO - If the flowmeter cable has correct continuity, the flowmeter has failed or needs repair. If the problem is lack of voltage when spinning the generator, remove the top plate (see the picture at the bottom of page 15) and inspect the wiring. Do not remove the generator unless calibration of the flowmeter is necessary. See pages 17-19 for flowmeter calibration (not normally required).
- (1) Engine load varying (governor surges; unstable load; loose linkage; cold engine; torque converter; etc.). The engine rpm should be stable.
- (2) Air in the fuel (invert the flowmeter temporarily at high idle to work air through the flowmeter).
- (3) Low battery voltage.
- (4) Bad seals in the female quick-disconnect couplers.
- (5) Lack of adequate pressure at the fuel flowmeter (on engines with a fuel filter before the transfer pump, additional pressurization may be needed; see Special Instruction Form GEG02402). Always use a clean fuel filter, especially when testing sleeve metering fuel systems.
- (6) Defective accumulator. See page 14.
- (7) Defective solenoid valve in the fuel bypass line (when used).
- (8) Actual flow is bypassing fuel filter. Example: D353 can have filter base gasket reversed so flow does not go through filter (and flowmeter) properly.
- (2) Air in the fuel (invert the flowmeter temporarily at high idle to work air through the flowmeter).
13. Are the GAL/HR (or Horsepower) readings relatively erratic when the flowmeter and readout box are connected to a running loaded engine (flow rate above 5 gph)?
a) NO - The GPH functions and flowmeter are operating correctly. Go to Step 14. See pages 17-19 if calibration errors are suspected.
b) YES - The following can cause erratic flow (or erratic horsepower) readings. Check each of the following:
If the above tests do not locate the problem, the following additional test may be performed before returning the unit to Fluidyne:
Connect the flowmeter and readout box to a fuel pump such as the one in the Fuel Injection Test Bench (see page 17). Do not connect the flowmeter to a fuel injection pump. Connect the test bench fuel supply hose to the input of the flowmeter, and the outlet of the flowmeter to the fuel supply tank (at the bottom front of the test bench). No accumulator is necessary. Use the gate valve on the test bench to vary the fuel rate. The readings should be very stable (within 0.3 gph over a minute or two). If the readings are not stable, the flowmeter or internal magnet may be binding or otherwise defective, or the readout box may be defective. NOTE: The readings will drop slowly as the flowmeter warms up to the fuel temperature. Determine which unit is defective and return it only to Fluidyne.
14. Turn the MODE switch to the HORSEPOWER CALIB. position. If the unit has been turned on for at least five minutes, is the horsepower calibrate value (top display) within the tolerance shown in the lid of the unit?
a) YES - If the values are relatively stable when the engine is running, the entire unit is basically operational. If intermittent problems exist but Steps 1 through 14 check correctly, return the unit to Fluidyne. (Be sure to review Step 13.) To check for correct horsepower values across the range, see page 10.
b) NO - Make sure the BSFC and FUEL DENSITY dials are set correctly and have not slipped on the shaft (see page 5). If the value is within 10 horsepower, the unit may only need to be calibrated. Refer to pages 11 and 12, and the Note in Step 10 on page 3. If the value is incorrect by more than 10 horsepower, or erratic, or "frozen" in the first four MODE switch positions, return the unit to Fluidyne.
15. To check for correct operation of the battery charging circuit, connect the unit to a fully charged 12 volt battery. Turn the POWER switch to the BATT. CHARGE position after observing the displayed battery voltage. Leave the switch in the BATT. CHARGE position for 20 seconds. If the charging circuit is working, the displayed reading will increase by at least 0.10 volts (unless the batteries are close to fully charged). If the charging circuit is not operating, check for a blown fuse or loose connections, then see page 7. If the problem is not corrected after checking the battery charging cable, return the power supply board and aluminum plate to Fluidyne for repair. If the batteries are discharged completely, check the fuses, then attempt to charge for at least 12 hours.
If the preceding 15 tests check correctly, the Horsepower Meter and related components are performing satisfactorily. If a problem exists that is not covered above, consult your Caterpillar Division Service Manager.
Setting The Fuel Density And BSFC Controls
The FUEL DENSITY control and BSFC control each has two basic parts - the dial mechanism and gears, and the potentiometer. The gear mechanism is designed to count approximately 100 units for each full revolution of the potentiometer shaft. The range of the FUEL DENSITY counter is .653 to .747 pounds per gallon; the potentiometer shaft therefore turns one revolution. The range of the BSFC counter is .299 to .601 pounds per brake horsepower per hour; its potentiometer shaft turns three revolutions.
The FUEL DENSITY and BSFC controls can be put out of adjustment with poor handling. To check the controls for proper calibration, loosen locking levers (1), and slowly turn the knob all the way to the left and then all the way to the right. See if there is any slipping of the gears. The counterclockwise limits should be the lower limit (for example, BSFC of .299). The clockwise limit should be the upper limit (BSFC of .601). If these limits are not correct, the dials should be reset to the potentiometer shaft as shown below. If the gears slip or are difficult to turn, either the shaft is bent or the gears are stripped. Replace the defective part. Sometimes it is possible to exchange the two controls as a temporary repair. For replacement of the gear mechanism shown, contact Helipot Division of Beckman Instruments, Inc., 2500 TR Harbor Blvd., Fullerton, California 92634, U.S.A., Telephone (714) 871-4845 for the name of a local distributor, or order directly from the above address. Specify a Model 205 "Digidial" turns-counting dial. Get replacement potentiometers from Fluidyne Instrumentation; see page 49. NOTE: Serial number 1105-up use a different mechanism than shown below. These may be removed in a similar manner after first removing the knob. Order replacement dials (Stock No. 12F4492) from Newark Electronics, 500 N. Pulaski Rd., Chicago, Illinois 60624, U.S.A.
(1) Push up on release locking lever (1). Remove cover (2) by pulling straight up. Use the Allen-head wrench (3) to loosen the two setscrews in knob (4). Remove the knob. Turn the potentiometer shaft (5) all the way counterclockwise. This is the minimum setting. With the knob removed, turn dial (6) until the minimum setting (.299 for BSFC or .653 for FUEL DENSITY) is at the top of the dials.
(2) Carefully install knob (4) and tighten both setscrews while holding dial (6) and the readout at the minimum setting. Check the setting by turning the knob to the full clockwise stop. The readout should be the maximum value (.601 for BSFC and .747 for FUEL DENSITY). If the setting is not exactly correct, change the position of the knob on the shaft until the amount of any error is the same between the two stops. For example, if movement is from .300 to .598 change the knob to show .301 to .599 movement. The error in the working range will be very small. Install cover (2).
Checking Power Supply And Battery Charging Circuits
NOTE: The following procedure applies to Horsepower Meters with either two or three batteries.
Power Supply Circuit
(1) Carefully remove panel (1) from the top of the Horsepower Meter by removing the six screws.
(2) Check the battery clips to be sure that the pink leads are connected to the positive (red) battery terminals (2) and the black leads are connected to the negative (black) terminals (3).
(3) Check the batteries to make sure they have enough voltage. The "BATT. TEST" position should indicate 5.30 volts or greater. The voltage measured across the battery terminals should be 6.00 volts or more.
NOTE: When the battery voltage (displayed reading) is less than approximately 4.90 volts, the Horsepower Meter display circuit will not work correctly. The circuit will give a random readout at approximately three times the normal display rate, the display lights will become dim, and the calibration values may be incorrect.
(4) Remove fuses (4) and check them for continuity using an ohmmeter.
| NOTICE |
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Do not use an ohmmeter to check components on either printed circuit board. |
(5) Connect the negative lead of a voltmeter to P4-8 on the connector. Turn the Horsepower Meter on, and check for the following voltages with the positive lead of the voltmeter connected as indicated.
NOTE: The P4 locations are shown on the power board loading diagram on page 40 or 42.
The displayed battery test voltage should be within 0.15 volts of the voltage at P4-6 with the instrument ON. Any unidentified problems are caused by switches or connections which are open or shorted.
Battery Charging Circuit
(1) Connect the charging cable to a fully charged 12 volt battery.
NOTE: The charging input must be a minimum of 11 volts to properly activate the voltage regulator.
(2) Turn the mode switch to the "BATT. TEST" position.
(3) Turn the Horsepower Meter ON and record the displayed voltage.
(4) Turn the power switch to the "12 V D.C. BATT. CHARGE" position for one minute.
(5) Turn the power switch to the ON position, and look at the displayed voltage reading. If the charging circuit is working correctly, there will be a definite increase in the displayed voltage. This reading may drift downward rapidly.
(6) If there is an increase in the voltage reading but the batteries will not charge or hold a charge, remove the batteries and check them for leakage around the terminals and the three serrated ports. If a "gell/cell" battery charger is available (see Special Instruction Form GEG02402), use this battery charger to charge the batteries. If this battery charger is not available or if the batteries are leaking, replace the batteries.
(7) If there is no increase in the displayed voltage reading in Step 5, check fuse F1 for continuity. Disconnect the battery connectors, turn the power switch to the "12 V D.C. BATT. CHARGE" position and measure the voltage at the battery connectors. This voltage should be approximately 7.2 volts. If the voltage is correct, the batteries are defective.
(8) For further troubleshooting, remove the power board from the case and disconnect the main board connector and the battery connectors.
(9) Apply 12 V D.C. positive to P4-12 and 12 V D.C. negative to P4-8.
NOTE: The P4 locations are shown on the power board loading diagram on Page 40 or 42.
(10) Connect the voltmeter positive lead to the junction of R65 and R66 and the negative lead to P4-8. The maximum reference voltage should be 1.725 volts and the minimum 1.690 volts.
(11) Check voltage regulation with the digital voltmeter positive lead to P4-14 and the negative lead to P4-8. Put a 3 ohm 20 watt resistor across P4-14 and P4-8. The voltage should not drop below 7.00 volts.
(12) Put a 2 ohm 20 watt resistor across P4-14 and P4-8. Check the current through the 2 ohm resistor by using an accurate ammeter, or measure the voltage across R64 and calculate the current. The maximum current should be 2.6 amperes; minimum current should be 2.25 amperes. The current is limited with this load.
(13) If any of the values in Steps 10, 11, or 12 are outside the specifications given, either the voltage regulator or Q41 or Q42 has failed. The most likely failure would be in the voltage regulator.
(14) To check the 24 volt protection circuit, remove fuse F1 and replace it with a 100 ohm 1% 1/2 watt resistor.
(15) Place the voltmeter across the 100 ohm resistor.
(16) Apply a variable DC voltage source (0 to 24 V DC) with the positive lead to P4-12 and negative lead to P4-8.
(17) Increase the voltage from zero until the voltage across the 100 ohm resistor increases rapidly to approximately the applied voltage. This voltage should be less than 20 volts and more than 15 volts. If this voltage is not correct, the problem is in CR12 or CR13.
Checking Tachometer Circuit
NOTE: Use an accurate tachometer to check the tachometer circuit of the Horsepower Meter. The following procedure shows how to use the one on the Fuel Injection Test Bench. Use a tachometer generator that is known to work and is in correct adjustment (see Page 13).
(1) Install a J-23300-35 Adapter Plate (1) and J-23300-530 Pilot Adapter (2) on the test bench. The plate and adapter are part of the 1P1800 Test Housing Group.
(2) Install the 5P2151 Tachometer Drive Adapter (3), and tighten setscrew (4).
(3) Engage the drive adapter with the test bench drive.
(4) Install the tachometer generator (5) on the drive adapter.
(5) Use the tachometer cable to connect the tachometer generator to the Horsepower Meter.
(6) Install a 3B6483 Cap (6) on the end of the lubricating oil supply hose.
(7) Turn on the Horsepower Meter. Check operation in each MODE position except ENGINE SPEED VERIFY.
(8) Turn on the Fuel Injection Test Bench, and run it at several speeds. Compare the readings of the two tachometers. Tachometer (7) on the test bench should read one-half the value of the Horsepower Meter tachometer (8).
NOTE: If the test bench tachometer does not read one-half the value of the Horsepower Meter tachometer but readings are relatively close (and the Horsepower Meter tachometer readings are constant), the tachometer circuit in the Horsepower Meter is working correctly.
(9) If no reading is obtained on the Horsepower Meter tachometer, check the cables and connectors for open and short circuits.
(10) If the readings are erratic, check the tachometer circuit in the Horsepower Meter with a sine wave or square wave signal generator and oscilloscope. With the input wave signal set at 1 volt peak-to-peak, the Horsepower Meter will show an engine rpm of six times the signal frequency; see the topic ELECTRONIC TROUBLESHOOTING on Page 24. Erratic readings can be caused by fluctuating engine rpm, intermittent electrical connections, or an external noise source. For the latter, use a shielded 9S3048 Cable Assembly between the Horsepower Meter cable and the tachometer generator.
Checking Flow Rate Circuit
(1) Make sure the Horsepower Meter batteries are charged. The readouts should be lighted when the Meter is turned ON.
(2) Turn the MODE switch to the GAL/HR CALIB position. The displayed value on the upper readout should be the same as the GAL/HR CALIB value in the lid of the Meter. Permissible tolerance is ± 0.2 gph.
NOTE: The FUEL DENSITY and BSFC dials have no effect on gallon-per-hour readings.
(3) If the displayed value is not correct, perform the flow rate calibration procedure on page 16.
(4) If no reading is obtained, check the input circuit for broken connections, defective components, etc. See the topic ELECTRONIC TROUBLESHOOTING on page 24.
Even if the flow rate calibration value is correct, the flow rate circuit should be checked periodically at various flow rates to check accuracy. The following tools are necessary: a) a well-regulated variable DC voltage source of 0 to 35 volts, b) a calibrated 3 1/2 or 4 1/2 digit digital voltmeter and c) test leads.
(5) Turn on the Horsepower Meter, the power supply, and the digital voltmeter. Let them stabilize for about 15 to 20 minutes.
(6) Make sure the voltage output of the power supply is less than 3 volts. Connect the power supply to the FLOWMETER socket. Pin B of the socket is positive; pin A is negative; pin C is not used.
(7) Vary the voltage input through the range of 0.098 to 3.125 volts.
(8) The displayed flow rates should agree closely with the values shown below. The flow rate should vary linearly with the input voltage except at the extreme ends of the range. Allow a variation of ± .2 gph for any flow rate less than 6 gph or greater than 80 gph. Allow a variation of ± .1 gph for flow rates between 6 and 80 gph.
(For other voltages, use the formula: Desired displayed flow = Input voltage × 32.)
(9) If the correct flow rates cannot be obtained, perform the calibration procedure shown on page 11.
(10) If the calibration procedure cannot be performed satisfactorily, there is probably a circuitry problem. See the topic ELECTRONIC TROUBLESHOOTING on page 24.
Checking Horsepower Circuit
(1) Be sure the Horsepower Meter batteries are charged. The readouts should be lighted when the Horsepower Meter is turned ON. The settings of the FUEL DENSITY and BSFC dials have a direct effect on all horsepower readings.
IMPORTANT: The flow rate circuit must be calibrated and operating correctly in order to check the horsepower circuit.
(2) Check the positions of the FUEL DENSITY and BSFC dials on their respective potentiometer shafts as shown on page 5. If correct, set the FUEL DENSITY dial to 7.00 and the BSFC dial to .400. Lock the dials in place using the locking levers.
(3) Turn the MODE switch to the HORSEPOWER CALIB. position. The displayed value on the upper readout should be the same as the HORSEPOWER CALIB. value shown in the lid of the Meter. The permissible tolerance is ± 4 horsepower (± 3%).
(4) If the displayed value is not correct, perform the calibration procedure shown on page 11. If there is no reading, see the topic, ELECTRONIC TROUBLESHOOTING.
To check the accuracy of the horsepower calculations over the entire range of flow rates, BSFC values, and fuel densities, use the same tools as for calibrating the flow rate circuit.
(5) Turn on the Horsepower Meter, the power supply, and the digital voltmeter. Allow them to stabilize for about 15 to 20 minutes. Make sure the voltage output of the power supply is less than 3 volts. Connect the power supply to the FLOWMETER socket. Pin B of the socket is positive; pin A is negative; pin C is not used. Vary the voltage input through the range of 0.098 to 3.125 volts.
(6) The displayed horsepower values should agree closely with those shown below. The horsepower readings should be within .5% in the range of 100 to 1200 horsepower and within approximately 1% outside of this range. If the readings are not within these limits, perform the calibration procedure shown on page 11. If the calibration procedure cannot be performed satisfactorily, there is probably a circuitry problem. See the topic ELECTRONIC TROUBLESHOOTING on page 24.
For other voltages, use the formula: Displayed Horsepower = Input Voltage × 560 (with FUEL DENSITY of 7.00 and BSFC of .400)
(7) Vary the FUEL DENSITY and BSFC dials from approximately 6.75 to 7.25 and from .375 to .425 respectively. Use the following formula to check the calculations:
(8) The displayed results should be within 1% of the theoretical values over the entire range of possible combinations.
Calibrating The Engine Horsepower Meter
The following tools are necessary to perform the calibration procedure: a) an accurate and stable voltage source capable of resolving 10 microvolts, and b) a 4 1/2 digit digital voltmeter with an accuracy of at least .1% and a resolution of at least 10 microvolts. Whenever making voltage measurements, connect the voltmeter common lead to wiring point "B" on the Horsepower Meter. See the schematic on pages 35-36 or 37-38 and the loading diagram on pages 39-40 or 41-42 for reference to locate the test points (TP's).
Turn ON the Horsepower Meter, the power supply, and the digital voltmeter. Let them stabilize for about 15 minutes.
NOTE: Difficulty in obtaining or maintaining any of the following adjustments is probably caused by an active component that is out of specification; see the section ELECTRONIC TROUBLESHOOTING. For normal calibration, it is not necessary to separate the circuit board from the face panel.
Digital-To-Analog Converter (DAC) Adjustment
(1) Solder a temporary jumper across TP2.
(2) Turn the MODE switch to the ENGINE SPEED VERIFY position.
(3) Connect the digital voltmeter to the analog output pin of the DAC.
(4) Adjust the DAC zero trim potentiometer (R44) for 0.000 on the digital voltmeter.
(5) Remove the jumper from TP2.
Amplifier Offset Adjustment
(1) Connect the digital voltmeter to wiring point "L" (or TP3).
(2) Turn the MODE switch to the ENGINE SPEED VERIFY position.
(3) Adjust the amplifier offset trimmer potentiometer (R25) for 0.000 on the digital voltmeter.
Comparator Offset Adjustment
(1) Set the voltage source to 62.50 millivolts, and connect it to the flowmeter connector - minus to pin A and plus to pin B.
(2) Turn the MODE switch to the GAL/HR position.
(3) While observing the gal/hr readout on the Horsepower Meter, adjust the comparator offset trimmer potentiometer (R42) for a reading of 2.0 gal/hr.
Fuel Flow Span Adjustment
(1) Set the voltage source to 2.500 volts, and connect it to the flowmeter connector - minus to pin A and plus to pin B.
(2) Turn the MODE switch to the GAL/HR position.
(3) Attach the digital voltmeter to wiring point "L" (or TP3).
(4) Adjust the density trimmer potentiometer (R26) for a reading of 10.000 volts.
(5) Attach the digital voltmeter to wiring point "T".
(6) Solder a temporary jumper across TP2.
(7) Adjust the fuel trimmer potentiometer (R28) for a reading of .8000 volts.
(8) Remove the TP2 jumper.
(9) Observe the gal/hr readout on the Horsepower Meter, and adjust the DAC full scale trimmer potentiometer (R45) for a reading of 80.0 gal/hr. Center the trimmer rotation midway between 79.9 and 80.1 gal/hr.
(10) Adjust the calibration voltage source to 62.50 millivolts, and check for a reading of 2.0 gal/hr. If this reading cannot be obtained, repeat the COMPARATOR OFFSET ADJUSTMENT.
(11) Recheck calibration steps 1 through 10, and make adjustments as necessary.
Horsepower Span Adjustment
(1) Set the voltage source to 2.500 volts, and connect it to the flowmeter connector - minus to pin A and plus to pin B.
(2) Turn the MODE switch to the HORSEPOWER position.
(3) Check the FUEL DENSITY dial for a minimum-maximum range of 6.53 to 7.47. Set the dial to 7.00.
(4) Check the BSFC dial for a minimum-maximum range of .2985 to .6015. Set the dial to 0.400.
(5) Adjust the BSFC trimmer potentiometer (R31) for a reading of 1400 horsepower.
Checking And Adjusting The Tachometer Generator
NOTE: The tachometer generator is the same one used with the 9S2000 Hydraulic Flowmeter and the 1P5500 Phototach. These instruments can be used to find out if the tachometer generator is defective. If neither instrument is available, a good quality voltmeter or an oscilloscope can be used.
(1) Connect the tachometer generator to the flowmeter or the phototach. Rotate the shaft or the generator rapidly by hand. A small movement of the needle usually indicates that the tachometer generator is operative. (When connected to the Horsepower Meter, readings will be in the range of 300-500 rpm when turned by hand).
(2) Use an ohmmeter to check the resistance of the magnetic transducer. The correct value is 3200 ± 640 ohms. If the generator is faulty, replace it with a new one. If the generator passes both tests, check the tachometer cable for short or open circuits; then check the tachometer circuit of the Horsepower Meter as shown on page 8.
(3) The tachometer generator produces one signal pulse for each six rpm of the engine. This pulse rate is multiplied within the Horsepower Meter. The sensitivity of the tachometer generator is in relation to the distance from the magnetic transducer to the gear teeth on the drive shaft. If the transducer is too far from the gear teeth, no reading will occur at any engine speed. Use the following procedure to adjust the tachometer generator.
(4) Loosen locknut (1). Turn magnetic transducer (2) clockwise while rotating drive shaft (3) manually. The drive shaft gear teeth can be felt by touching the end of the transducer when the adjustment is correct. Hold transducer (2) while tightening locknut (1). Check the adjustment after tightening the locknut by again rotating drive shaft (3). It should be possible to feel each tooth.
(5) If cable tie (4) has been removed, install it. Put epoxy at location (A) if the output cable insulation has pulled away from the transducer but the connection is otherwise good.
Checking And Charging The Accumulator
The accumulator, which is connected with the hoses to the fuel flowmeter, works as a pulse dampener for backward pulses transmitted from the fuel injection pumps toward the fuel flowmeter. These pulses are caused by the closing of the fuel injection plunger ports. Such fuel line surges cause the flowmeter pistons (because of their low frictional losses) to move in a backward direction. Backward movement of the pistons causes the flowmeter to give incorrect measurements of fuel flow. The accumulator serves to dampen these pulses.
To check the accumulator, connect the fuel flowmeter, accumulator, and hoses to an operable engine as usual. Feel the fuel flowmeter hoses at the point where one hose returns fuel to the fuel system (just before the injection pump housing). The pressure surges from the injection pumps probably can be felt at this point. Continue to feel these surges along the hose back toward the accumulator. The surges should become less noticeable. At or near the point that the hose connects to the fuel flowmeter, the surges should not be felt at all if the accumulator is working properly.
Inside the accumulator is a special bladder which is resistant to diesel fuel. This bladder is pressurized with a nitrogen precharge of 6 psi (0.4 kg/cm2). Check this charge of nitrogen at least every 12 months. If the precharge is lost, recharge the accumulator with nitrogen using the 7S5437 Nitrogen Charging Group as shown in the following procedure.
NOTE: It is not necessary to disconnect the hoses from the accumulator in order to charge it.
 |
Do not charge the accumulator with oxygen; however, charging with dry air is permissible. Always use extreme care when handling high pressure gas cylinders. |
 |
(1) Remove screw (1) and the support disc from the end of the accumulator. Install 5P2963 Charging Adapter (2). Install the gauges and regulator (3) from the 7S5437 Nitrogen Charging Group on the nitrogen tank. Install the valve, fittings, hose, chuck, and 7S8713 Gauge (4) on regulator (3).
(2) Connect chuck (5) to adapter (2). With valve (6) closed, open the valve on the nitrogen tank. Slowly open valve (6) until there is slightly less than 25 psi (1.8 kg/cm2) reading on gauge (7). CAUTION: Do not exceed 30 psi (2.1 kg/cm2) or the gauge can be damaged in the next step.
(3) Disconnect chuck (5) from adapter (2). Use an accurate low pressure gauge and a suitable chuck to bleed the pressure down to 6 ± 2 psi (0.4 ± 0.14 kg/cm2). Do not exceed 8 psi (0.5 kg/cm2) pressure or the dampening effect will be lost. The parts shown are the 0-30 gauge psi (8) from the 9S8140 Pressurizing Pump, 3B6768 Bushing (9), and chuck (10) from the 7S9394 Connection Assembly. Remove adapter (2), and install the washer, disc, and screw.
Fuel Flowmeter General Information
The fuel flowmeter has four radial pistons and built-in sequence valves which measure the fuel flow. Fuel enters the center portion of the flowmeter and passes through the uncovered port P1 to the face of piston No. 1, and moves it inward. As piston No. 1 moves, it turns the crankshaft clockwise; this clockwise motion causes piston No. 3 to force its fuel out through the passage and port P3 to exhaust port (E). This sequence repeats alternately with the other pistons on each one-quarter revolution of the flowmeter crankshaft. When one piston is the driving piston, the piston directly opposite it is the delivering piston. The fuel flowmeter has extremely low frictional losses and offers little resistance to fuel flow.
The fuel flowmeter crankshaft is magnetically coupled to a very accurately calibrated linear DC generator which creates a signal of a voltage directly proportional to the fuel flow rate. This DC signal is transmitted to the Horsepower Meter where it is changed into a gallons per hour figure and displayed, or used for horsepower calculations.
Fuel Flowmeter Wiring
NOTE: Effective with approximately flowmeter serial no. 1162 and up, the resistance values were changed to 50K ohm for the potentiometer and 150 ohm (1%) for the resistor.
Fuel Flowmeter General Checks
(1) To check whether there is a defect in the fuel flowmeter and not the Horsepower Meter, apply a small voltage (less than 3 volts) to the FLOWMETER connector on the Horsepower Meter. Always connect the positive source lead to the "B" pin, and the negative lead to the "A" pin. The GAL/Hr reading should equal 32 times the voltage. For example, a 1 1/2 volt cell should give a gallons per hour reading of approximately 48 gal/hr. If there is no reading with the cell connected as above, the problem is in the Horsepower Meter.
(2) If the Horsepower Meter reads the correct gallons per hour reading as shown in the above step, check the continuity of the flowmeter cable. If the problem is not in the flowmeter cable, unscrew the generator section (1) from the flowmeter housing. Rotate magnet (2) counterclockwise by hand (with the flowmeter still connected to the Horsepower Meter). If there is a flow indication, the generator section of the flowmeter is operational. Inspect magnet (2). If more than 20% of the magnet is missing, obtain a new one from Fluidyne. (The magnet must be tight in its holder, and the holder must be tight on the generator shaft.)
(3) Remove the four cover plates (3), and carefully push on the four pistons in the letter sequence A-B-C-D as shown. The pistons should move with relative ease, and the shaft under magnet cover (4) should turn. All pistons should move in and out. If they do not, a connecting rod may be broken or off the crankshaft. When installing plates (3), always put the recess (E) in the plate in alignment with hole (F).
| NOTICE |
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Do not remove magnet cover (4) unless further disassembly is necessary, since removal may cause the piston connecting rods to be separated from the crankshaft. Further disassembly makes calibration of the flowmeter necessary. |
(4) If the pistons move freely and there is no sign of excessive wear or contamination, there was probably an air lock on one piston. Assemble the flowmeter and again check the operation.
NOTE: After assembly of the flowmeter, operate the flowmeter for at least one hour at 15 gallons per hour or more before checking calibration or before recalibrating as shown on page 17.
Fuel Flowmeter Calibration
Preliminary Checks
Check and/or calibrate the gallon per hour circuit of the Horsepower Meter to make sure it is accurate.
- 1. A fuel supply with very stable fuel temperature, and flow controls with the ability to quickly start and stop flow into a receptacle calibrated in divisions of 1 cubic centimeter (milliliter) or less.
NOTE: In the following procedure, the Caterpillar Fuel Injection Test Bench is used. If the test bench is used for calibration, a new or recently rebuilt fuel injection pump is needed. The pump should be as large as possible with preferably 6 pumps (maximum). In the procedure below, a D8 (D342) pump group is shown.
- 2. A stopwatch with marked divisions of at least hundredths of a minute and tenths of a second.
- 3. The necessary fittings and hoses to connect the fuel flowmeter to the fuel supply.
- 4. An accurate thermometer (160°F minimum).
- 2. A stopwatch with marked divisions of at least hundredths of a minute and tenths of a second.
Calibration
(1) Install the fuel injection pump group on the test bench. Do not connect the fuel supply hose. Install a 3B6483 Cap (1/4" pipe thread) on the lube oil hose to prevent oil loss when the bench is turned on.
NOTE: It is preferable to remove the torque spring and spacers in order to get maximum rack movement.
(2) Install a 3P2235 Nipple (1) and a 3B7722 Reducing Bushing (3/8" pipe thread to 1/4" pipe thread) on the test bench fuel supply hose (2). The special connector on the hose mates with the 1/4" pipe thread. Do not use standard straight thread adapter; it can damage the connector.
(3) At the point where the fuel supply hose (2) would normally connect to the fuel injection pump housing, install a 3B6553 Elbow (3), 3P7262 Pipe Nipple (4), 3B7722 Reducing Bushing (5), and 3P2235 Nipple (6).
(4) Connect fuel supply hose (2) to the "IN" port of fuel flowmeter (7). Connect accumulator (8) and hose (9) to the flowmeter as shown. Connect hose (10) to nipple (6) on the pump housing.
(5) Turn on the Fuel Injection Test Bench, and bleed the air from the pump and lines. Let the system warm up to approximately 110° to 120°F (use the thermometer on the test bench).
(6) Connect cable (11) between Horsepower Meter (12) and fuel flowmeter (7). Turn the Horsepower Meter on and turn mode switch (13) to the GAL/HR position.
NOTE: The settings of the FUEL DENSITY and BSFC controls are not important in this test. During the test, the flowmeter must be positioned with cable (11) up as shown.
(7) Run the fuel injection pumps at as high a delivery rate as possible and at a relatively high rpm. The exact gallon per hour flow rate displayed on the Horsepower Meter is not important, but use a setting stable within approximately ± 0.2 gallons over a five minute period or longer. Once the procedure is started, do not change the bench settings (including the fuel and lube heater switches).
(8) After the fuel flow and temperature have stabilized, pump at least 5 deliveries of fuel into the large (150 ml) graduates. Determine the number of strokes at the chosen flow that consistently delivers between 140 and 150 ml of fuel to each graduate.
(9) To check the flowmeter calibration, run at least three delivery checks with the fuel hot.
IMPORTANT: Unlike the normal test bench procedure, the graduates must be dry before each delivery check. Normally, with only a 10-second drain time, about 2 ml of fuel will remain on the walls and at the base of the graduate. Let the graduates drain at least 5 minutes between deliveries, and wipe the lip of each graduate with a clean, soft tissue.
(10) Make a record of the following readings:
1. Initial fuel temperature before delivery using the test bench thermometer.
2. Final fuel temperature after delivery using a thermometer (14) in one of the graduates. Stir the fuel while taking the temperature.
3. Fuel delivery to each graduate to the nearest tenth of a milliliter (cc).
4. Time of the test using an accurate stopwatch. Start the stopwatch when the test bench START button (15) is pushed and stop it when the counter reaches the preset number of strokes.
5. Gallons per hour reading (16) on the Horsepower Meter during the test. Use an average value if the reading fluctuates; however, the reading should not vary more than ± 0.1 gph.
(11) Use the following formulas for each test to calculate the flow rate, then correct the result for the temperature rise in the fuel injection pumps.
(12) Make at least three runs with hot fuel before making any adjustments to the flowmeter. If an adjustment is necessary, remove cover (17) and turn the small screw on potentiometer (18) while maintaining a steady flow rate. Clockwise rotation increases the displayed value. Several turns may be necessary for a change in the displayed value.
(13) After a change in the calibration, make at least three additional tests to verify the new setting.
NOTE: The 5P2148 Flowmeter can be overhauled to like-new condition and recalibrated by Fluidyne Instrumentation (see page 49 for address). A flat-rate charge of $175.00 (subject to change without notice) will be made, plus charges for any additional main parts required.
Fuel Flowmeter Disassembly
(1) Loosen the four setscrews (1), and remove cover (2) from the inner sleeve. Remove the two screws (3).
NOTE: If necessary, heat screws (3) with a soldering iron to loosen them. Remove the two retainers (4), and pull out the springs and brushes. Loosen setscrews (5), and remove inner sleeve (6) from outer sleeve (7). Remove outer sleeve (7) from the flowmeter.
(2) Loosen setscrews (8) and slide generator (9) out the top of the inner sleeve.
NOTE: Further disassembly of the generator makes recalibration of the flowmeter necessary. Remove the two screws (10), cover (11), flat washers (12), and wave washer (13).
(3) Remove the three screws (14) and body (15) from the generator. Carefully wipe the commutator and brushes clean with carbon tetrachloride. Do not put the entire assembly into the solvent. Let the parts become dry before assembling the generator.
NOTE: The circular magnet still operates correctly, even if small pieces or a section are broken off. Use a light coating of epoxy cement to hold the magnet in its holder.
(4) Remove and inspect couplers (16) and the 5P4772 Seals inside the couplers. Remove the four screws (17) and bottom plate (18) from the flowmeter. Remove ring (19), filter (20), and plate from bottom plate (18). (If disassembly is necessary, install a new filter and all O-rings. A 5P4179 Repair Kit contains all necessary items.) Remove the four side covers (21). Do not remove magnet cover (22) at this time.
(5) Put an identification and alignment mark on each piston (23) respective to its position in housing (24). IMPORTANT: The pistons must be installed back in their original positions in the housing. Remove magnet cover (22). Lift crankshaft (25) out of the housing. Slide pistons (23) out of the housing by gently pushing on connecting rod (26). The connecting rod bearings (27) are not available separately. The connecting rod and piston are matched and must be ordered as an assembly.
Fuel Flowmeter Assembly
(1) Use clean diesel fuel as a lubricant on the pistons, connecting rods, and crankshaft. Install pistons (1) one at a time in housing (2); put the housing on its side and slide crankshaft (3) in. Use a pointed rod (4) as a guide for the connecting rod. Install magnet cover (5).
NOTE: Install the pistons in their original positions in the housing and in the correct sequence. Install the first and third pistons with the connecting rod offset toward the top of housing (2). Install the second and fourth pistons with the offset toward the bottom of the housing.
(2) Install the four cover plates (6) so each recess (A) is in alignment with each hole (B) in the housing. Install plate (7), filter (8), and retaining ring (9) in bottom plate (10). Put plate (10) in position on housing (2), and install the four screws (11). Install couplers (12) in bottom plate (10).
(3) Put body (13) in position on armature assembly (14) and install the three screws. Install the two flat washers (15), wave washer (16), cover (17), and screws (18) on body (13).
NOTE: Wave washer (16) must be installed next to cover (17); and cover (17) must be installed with notch (C) in the cover in alignment with groove (D) in body (13).
(4) Turn inner sleeve (18) to install it on housing (2). Put generator (19) in position in the inner sleeve. Push down on the generator until it is in contact with magnet cover (5); then lift the generator about 1/16" (1.5) and tighten the two setscrews (20).
(5) Install outer sleeve (21), and tighten all setscrews (22). Install the springs and brushes (23), and retainers (24) in the generator.
(6) Connect wire (25) to the No. 1 terminal, and wires (26) to the No. 2 terminal of the generator with screws (27). Put cover (28) in position in the inner sleeve, and tighten setscrews (29) evenly.
NOTE: If the generator was disassembled and/or the pistons removed, calibration of the fuel flowmeter is necessary. See the section, FUEL FLOWMETER CALIBRATION.
Electronic Troubleshooting And Repair Of The Engine Horsepower Meter
General Information
| NOTICE |
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This section gives information necessary for repair of the Engine Horsepower Meter. Repairs should be made only by a technician with experience in digital circuitry, and in a laboratory equipped for such work. |
The troubleshooting flow charts on pages 51 and 53 give a step-by-step troubleshooting procedure for repair of the main board of the Horsepower Meter. The flow charts mainly show active components; however, failures can also be caused by passive components and by defects in foil and solder connections between the active components. All measurements in this section are taken with the negative lead of the test instrument connected to wiring point B on the Horsepower Meter.
The following tools are needed: a) a voltage source that has enough accuracy and stability to give a resolution of 10 microvolts, b) a 4 1/2 digit digital voltmeter with an accuracy of at least .1% and a resolution of at least 10 microvolts, and c) an oscilloscope.
The lights and 7447's can be checked by interchanging a suspected defective component with a known good one. Horsepower Meters No. 1001 through 1043 (except units with cover plate (17) shown below) must be returned to Fluidyne Instrumentation for repair if there is a light failure. The lights in other units can be changed from the front of the face panel by removing the two screws under the Service Tool decal (Form GEG00056) and the cover plate. If the suspected light is good, interchange the plug-in 7447 integrated circuit behind the light with a known good one. If neither the light nor the 7447 is defective, return the unit to Fluidyne for repair.
NOTE: There is no 7447 for the first digit in the top display. When installing the cover plate, use 7M7260 Liquid Gasket Material to seal the cover plate to the face panel, if there is no gasket.
Pin designations of the active components and the segment designations of the readout lights are shown above.
Removal Of Main Board
| NOTICE |
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Always turn off the Horsepower Meter before removing or installing the face panel. |
(1) Remove digi-dial covers (1); see page 5 for later units. Loosen the screws in knobs (2), and remove the knobs. Remove nuts (3) and digi-dials (4). Loosen the screws in knobs (5), and remove the knobs. Remove six screws (6). Remove face panel (7) by rocking and tipping the panel until it is clear of the lip of the case. CAUTION: Be careful not to damage the panel or the two switches (8) when removing the panel. Disconnect wiring plug (9) and vent tube (10) from the power board.
(2) Remove the four screws (11) from each of the three connectors (12).
NOTE: Screw (13) in the tachometer connector also uses a nut to hold ground wire (14) in position. Remove the two mounting screws (15) from the main board. Remove main board (16) from the face panel.
Installing Main Board
| NOTICE |
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Make sure the Horsepower Meter is turned off before installing main board and face panel. |
(1) Put main board (1) in position on face panel (2), and install the two screws (3). Install the four screws (4) that hold connectors (5) and (6) to the panel. Install four screws (7) and nut in tachometer connector (8). Use the nut to hold ground wire (9) in position on the connector.
(2) Connect wiring plug (10) to the power board with the number "1" on the plug to the left in the view of the box as shown. Connect vent tube (11) to the plate. Carefully install panel (2) on the case; be sure to put the vent tube in the left side of the case so it is not on top of the circuitry on plate (12). Install the six screws that hold the face panel in position.
(3) Install the knobs on the two mode switches, and tighten the setscrews. Put the digi-dials in position on the potentiometer shafts, and install the nuts. CAUTION: Do not tighten the nuts enough to bend the plastic base of the digi-dials. Carefully install the knobs on the digi-dials making sure the teeth on the knobs are in correct alignment with the gears on the digi-dials. Tighten the setscrews that hold the knobs in place on the digi-dials. Install the covers on the digi-dials.
NOTE: After installation of the main board and face panel, check the calibration of the Horsepower Meter. If new components have been installed, calibration may again be necessary. See the topics, SETTING THE FUEL DENSITY AND BSFC CONTROLS and CALIBRATING THE ENGINE HORSEPOWER METER.
Main Board Circuit Functions
GAL/HR And Horsepower Circuitry
NOTE: The following pages describe the circuitry used in Horsepower Meters 1001-1104. Later units function in a similar manner with the following exceptions:
- a) Later units have three batteries and a different BATT. CHARGE connector. For the 5 volt logic circuit, two transistors (Q44 and Q45) and associated components were added.
- b) Some of the functions of Q7 and Q9 were eliminated in the later units.
- c) The 7405 integrated circuit Q22 was changed to Q24, and one function was removed.
- d) The 74121 integrated circuit Q24 was changed to Q25 (a 74123 integrated circuit), and associated components were added.
- e) All semiconductors from Q25 through Q38 were renumbered to Q26 through Q39.
- b) Some of the functions of Q7 and Q9 were eliminated in the later units.
- 1. FLOWMETER INPUT The DC signal from the fuel flowmeter is directly proportional to the fuel flow rate (in gph). The flowmeter output signal is internally adjustable and is equal to 32 gph flow per 1.000 volt input to the Horsepower Meter.
- 2. CALIBRATION REFERENCE VOLTAGE During gal/hr or horsepower calibration checks, a built-in DC reference voltage (approximately 2.5 volts) is substituted for the above flowmeter input signal. This calibration reference voltage is determined by the value of zener CR2. During calibration checks, this voltage is displayed as approximately 80 gph (2.5V x 32gph/volt) or 1400 hp (80gph x 7.00 lb/gal ÷ .400 BSFC).
- 3. ACTIVE FILTER Q1, Q2 The typical flowmeter DC signal is not a "clean" signal at low flow rates due to the four piston construction of the flowmeter. Two (2) operational amplifiers (Q1, Q2) eliminate much of the AC ripple from the basic signal.
- 4. OPERATIONAL AMPLIFIER Q3 A third operational amplifier (Q3) with a gain of 4 is used to prepare the filtered DC signal for use in later stages.
- 5. GAL/HR AND HORSEPOWER CALIBRATE The same DC calibrate signal can be used for either gallons/hour or horsepower readouts, depending on the resistance ratios chosen. Various potentiometers and trimmer potentiometers (R26, R31, R30, R34 and R28) are used to calibrate the input signal for use in subsequent stages. For gph readings, R26 and R28 are used; for horsepower readings, R26, R30, R31 and R34 are used. The output of the calibration stage is fed to one input of the voltage comparator (Q23).
- 6. CLOCK CIRCUIT At the same time, a 2MHz crystal (X1) and related components furnish a stable oscillator pulse for use in both the flow circuits (gal/hr and horsepower) and the engine rpm circuits. This signal is fed to the counter circuit.
- 7. COUNTERS The 2MHz signal from the clock circuit is fed first to three decade dividers (Q27, Q31 and Q35); the output thus becomes a 2KHz signal. This 2KHz digital pulse is fed to three counters (Q36, Q32 and Q28). The counters supply the following outputs:
- a) The "1" output of Q36 to the tachometer circuit (Q4) for a reference signal for the "Speed Verify" reading (see below).
- b) The "800" output only of Q28 to a JK flip-flop (one half of Q26).
- c) All outputs to the Digital-to-Analog Converter (DAC).
- d) All outputs to the latches (Q29, Q33 and Q37) for the top display lights (gph and Hp readings).
- b) The "800" output only of Q28 to a JK flip-flop (one half of Q26).
- 8. JK FLIP-FLOPS (Q26) The two JK Flip-Flops associated with Q26 act like binary relays to trigger following stages.
The "800" output of the counters (Q28) feeds one half of Q26. This JK Flip-Flop feeds:
- a) to the Digital-to-Analog Converter (DAC) - 1000 position;
- b) to another JK Flip-Flop (other half of Q26); and
- c) to the latch control (Q25) for the tachometer circuit.
- b) to another JK Flip-Flop (other half of Q26); and
The second JK Flip-Flop controls the "1" digit in the 1000 position of the top (gph and Hp) display.
- 9. DIGITAL-TO-ANALOG CONVERTER (DAC) The DAC converts the digital pulse rate from the counters into a DC voltage. As the output pulses from the counters accumulate, the DAC's output voltage level increases linearly.
- 10. VOLTAGE COMPACTOR (Q23) The voltage comparator receives a voltage signal from both the DAC output and from the input "Gal./hr. - Horsepower Calibrate" network; the latter voltage is proportional to flow rate.
When the linear ramp voltage becomes the same magnitude as the input signal, the voltage comparator activates the monostable multivibrator (Q24).
- 11. MONOSTABLE MULTIVIBRATOR (Q24) This semiconductor causes the latches and second JK Flip-Flop to hold the count that is accumulated when the comparator voltages become equal. For example, if the input signal is 2.5 volts, the accumulated count is 800 for 80.0 gph or 1400 for 1400 Hp. For other voltages, the readings are directly proportional.
- 12. LATCHES (12A), DECODER-DRIVERS (12B), GPH DISPLAY LIGHTS (12C) These items provide display of the count that is held when the monostable multivibrator is activated by the voltage comparator. (In this example, the 2.5 volts input is equivalent to 80.0 gph - the decimal point is activated by the MODE switch position.)
- 2. CALIBRATION REFERENCE VOLTAGE During gal/hr or horsepower calibration checks, a built-in DC reference voltage (approximately 2.5 volts) is substituted for the above flowmeter input signal. This calibration reference voltage is determined by the value of zener CR2. During calibration checks, this voltage is displayed as approximately 80 gph (2.5V x 32gph/volt) or 1400 hp (80gph x 7.00 lb/gal ÷ .400 BSFC).
Tachometer Circuitry
- 13. TACHOMETER INPUT Engine speed is sensed using a magnetic pickup device that produces 10 pulses per engine revolution. This input signal is sinusoidal and varies in frequency directly with engine speed.
- 14. VOLTAGE COMPARATOR (Q4) The voltage comparator is used to convert the sinusoidal signal to digital square wave pulses of the same frequency.
The sinusoidal signal is fed to one input of a voltage comparator (Q4). A reference voltage derived from zener diode (CR1) is fed to the other input. When the magnitude of the sinusoidal input crosses that of the reference voltage, the voltage comparator puts out a pulse. This pulse is fed to a multiplier circuit.
- 15. MULTIPLIER CIRCUIT A multiplication of 60 allows engine speed to be read in one second (1 sec. time base) instead of waiting for one minute. The multiplier circuit first results in increasing the pulse rate by a factor of 8 times, then cancels out two pulses of each group of eight so the output becomes 6 times the input or 60 pulses per engine revolution. (The input signal from the tachometer generator is 10 times engine rpm.) This signal is fed to the counter control. (For 2400 rpm or 40 rev/sec, the input signal is 400 Hz which then becomes 2400 pulses fed to the counters.)
Multiplication is achieved by feeding the output of the voltage comparator directly to one input of an exclusive OR (Q6) and through a series of three inverters to the other input of the exclusive OR. The inverters delay the signal by an amount determined by the capacitance connected across the center inverter. The direct input causes a change of state in the exclusive OR which causes the output to change level. The delayed input from the inverters then causes the output to change level again. This process occurs on both edges of the pulse from the voltage comparator as shown pictorally below. Actual pulses are very brief and clustered more than shown.
The process is repeated through two more inverter-exclusive OR groups as shown below.
From the third exclusive OR, the pulses are fed both through an inverter and a binary counter (Q8) with its 2 and 4 outputs fed to a NAND. The first five pulses pass immediately through the inverter and are counted in the binary counter. The sixth pulse passes through the inverter, and after a short delay, causes the counter to change level. This places the output of the NAND low and the output of the inverter high for the next two pulses. These cancel algebraically and are not transmitted. The final output is as shown below.
These pulses are fed to a NAND (Q9) which serves as counter control. If the NAND is open, the pulses are fed to the counters (Q12, Q15, Q18 and Q21).
- 16. LATCH CONTROL As covered under the topic "GALLONS PER HOUR AND HORSEPOWER READINGS", the first JK Flip-Flop (Q26) feeds a signal to the tachometer circuit's Latch Control (monostable multivibrator Q25) once a second (every 2000 counts - the crystal oscillator clock, after the decade dividers, is running at 2000 Hz). This signal activates the latch control (Q25) which in turn activates the latches and also signals the counter control.
- 17. COUNTER CONTROL (17A), COUNTERS (17B) The NAND which serves as a counter control (Q9) turns the counters on and off. The rpm count (for example: 2400) is fed from the multiplier circuit through the counters. When the latch control is triggered once each second by the Latch Control, the counters are stopped.
- 18. LATCHES (18A), DECODER-DRIVERS (18B), RPM DISPLAY LIGHTS (18C) The latches receive the output of the counters and become latched when signaled by the Latch Control once each second. The stored count corresponds to engine rpm, and the value is decoded and displayed.
In the Engine Speed Verify mode, the one millisecond pulse from the counter Q36 is fed to the tachometer input of the voltage comparator (Q4). Due to the multiplication factor of six present in the RPM circuitry, the one millisecond pulse is displayed as 6000 rpm.
- 14. VOLTAGE COMPARATOR (Q4) The voltage comparator is used to convert the sinusoidal signal to digital square wave pulses of the same frequency.
Power Board Circuit Functions
POWER SUPPLY The power source consists of two or three 6 volt gelatin electrolyte batteries connected in parallel. The batteries are coupled to the power supply through switch (S2). The battery voltage is supplied directly to power the readouts. A Zener (CR14) is used to provide a regulated 5 volts for the logic circuitry. A DC-to-DC converter is used to provide a positive and negative 15 volts for the Operational Amplifiers and the Digital-to-Analog Converter.
CHARGING CIRCUIT The Horsepower Meter is designed to charge from a fully charged 12 volt battery. A minimum of 11 volts is necessary to operate the charging circuit. The GEL-CELL batteries will not be fully charged unless the charging source is at least 11.5 volts. Q41, Q42 and Q43 make up a current limiting voltage regulator which controls the charging current supplied to the batteries. Reverse polarity protection is provided by diode (CR11). Overvoltage protection is provided by SCR (CR12) and Zener (CR13). An overvoltage condition would trigger the SCR, cause a short circuit from the input to ground and cause Fuse F1 to blow.
If Fuse F2 blows, it signifies a problem in the RUN mode, probably a short or shorted component.
Fuse F1 may blow if the charging source voltage is poorly regulated. As the batteries accept charge, they draw less current and the source voltage may increase and blow the fuse without a problem existing.
Block Diagram Of Main Board Circuit Functions
NOTE: The numbers correspond to the circuit descriptions on pages 26 - 29.
Flow Rate And Horsepower Circuitry Troubleshooting Flow Chart
Tachometer Circuitry Troubleshooting Flow Chart
Schematic Of Engine Horsepower Meter (Serial No. 1001 - 1104)
Schematic Of Engine Horsepower Meter (Serial No. 1105 And Up)
Loading Diagrams Of Engine Horsepower Meter (Serial No. 1001 - 1104)
5P2152 Main Board
5P2165 Power Board
Loading Diagrams Of Engine Horsepower Meter (Serial No. 1105 And Up)
5P2152 Main Board
5P4187 Power Board
Electronic Parts List (Serial No. 1001 - 1104)
Main Board
Electronic Parts List (Serial No. 1105 And Up)
Warranty
The 5P2150 Engine Horsepower Meter and 5P2148 Flowmeter carry a one year warranty against defects in materials and workmanship. This warranty period begins with the date of delivery. To validate this warranty, the warranty card must be completed and mailed as explained on the card.
If a unit is received from Caterpillar in a damaged or defective condition, it should be returned to Caterpillar through regular warranty procedures. If a unit becomes defective after use, but before the warranty period expires, return it to one of the following repair stations. Out of warranty period, repair of a unit will also be performed at one of these stations. Further warranty procedural information is explained in the Caterpillar Warranty Guide bulletin "Warranty Practices - Service Tools", Form FEG00037-08.
NOTE: In the United States, Canada, Mexico, and Mid and South America, return the 5P2148 Flowmeter (only) to Fluidyne Instrumentation, 1420 Healdsburg Avenue, Healdsburg, CA 95448, attention Mr. John Max.
For repairs (after the warranty period) outside the United States and Canada, the customer will be billed for the cost of material and labor plus any transportation charges. A warranty credit will be issued if the equipment is in warranty and the warranty card is on file. If the equipment is found to be abused or otherwise not covered by warranty, the owner will be advised of the cost of repair before the work is completed.
