RING-RETAINING 1M4093 - Caterpillar

Some changes are necessary to the 6V2100 Multitach and 5P9698 Calibrator for correct operation. These changes are listed below.
Changes To 6V2100 Multitach
RPM indications on the 6V2100 Multitach can be in error when either the tachometer generator or magnetic pickup is connected to the MAG input at the same time a 6V4950 Injection Line Speed Pickup Group is connected to the PHOTO input. A resistor located on the printed circuit board inside the multitach must be changed to correct the problem.
Procedure To Change 6V2100 Multitach
1. All 6V2100 Multitachs built after July 1, 1982 have had the resistor changed at the factory. These units have the letter "A" on the end connector panel next to the 11 to 40 volt DC connector. See Illustration 1. Check to see if your multitach has this letter.2. For those multitachs which have not had the problem corrected and have no letter "A" on the connector panel, a resistor must be purchased from an electronic supply store. The resistor needed is a 220 k ohm 10%, 1/4watt carbon resistor.3. Remove the rear cover of the multitach as shown in the Special Instruction, "Using the 6V2100 Multitach," Form SEHS7807-01, Page 17. It is possible that the printed circuit board will also have to be removed.
Illustration 1. Identification mark after change is made to 6V2100 Multitach.4. Remove resistor R16 from the printed circuit board. See Illustrations 2 and 3. This is done with the application of heat from a small soldering iron. Use heat on the lead wires on each end of the resistor until the solder melts and the resistor can be lifted from the printed circuit board. Use needlenose pliers or a 5P1720 Oil Seal Pick to lift the resistor.5. Install the new 220 k ohm resistor in the location where resistor R16 was removed.
Illustration 2. Location of R16 and R15 resistors in 6V2100 Multitach.
Illustration 3. Location of R16 and R15 resistors in electronic diagram of 6V2100 Multitach.6. Check resistor R15 to see if it is in direct contact with the printed circuit board. See Illustration 3. There must be approximately 1.0 mm (.04") of clearance between the body of the resistor and the printed circuit board. If there is no clearance, use heat on the lead wire on one end of the resistor. Lift this end of the resistor with an oil seal pick when the solder melts. Do the same procedure on the lead wire on the other end of the resistor. Replace the rear cover on the multitach and make a test according to the procedure in the Special Instruction.7. Use a letter stamp or engraving tool to permanently mark a letter "A" on the connector panel, as shown in Illustration 1.Changes To 5P9698 Calibrator
The 6V6113 Amplifier, which is part of the 6V4950 Pickup Group, will test as bad when test procedures are done unless a resistor in the 5P9698 Calibrator is changed.
Procedure To Change 5P9698 Calibrator
1. All 5P9698 Calibrators built after July 1, 1982 have already had the problem