I spoke with Corey at SR Mariner Instruments today regarding my old, non-functioning SR Mariner KT-5 knot meter. He sent me the following troubleshooting info. Thought it might be helpful to others with the old SR Mariner analog knot meters... TROUBLESHOOTING SPEED TRANSMITTERS I. TR-5 - 2 wire transmitter used on KT-5, 5A, 6,7, DKT-5A and SK-5 A. Measure with an ohmmeter for a resistance value of approximately 2000 ohms (2K ohms). Please do not spin the paddlewheel during this procedure. 1. If unit is good, then visually inspect the paddlewheel for any broken paddles or missing magnets 2. If unit is open (infinite resistance), then unit needs to be replaced. or B. Measure with an AC voltmeter when the paddlewheel is spinning. You should get approximately 0.97 VAC at 5 knots of speed. II. TR-10 - 2 wire transmitter used on the Nav-5A and Nav-10 systems. A. Measure with an ohmmeter for a resistance value of approximately 5000 ohms (5K ohms). Please do not spin the paddlewheel during this procedure. III. TR-1 - 3 wire transmitter used on all KL units and DKL units. A. Apply +12 VDC to the RED wire and the GROUND (NEGATIVE) to the BLACK wires. 1. Measure actual voltage across RED and BLACK with DC voltmeter. 2. Disconnect the GREEN wire (if still connected to the display) and measure across the GREEN and BLACK. This voltage should be approximately 1 volt less than step 1. a. If good, then go to step 3. b. If not even close to the proper voltage, sending unit needs replacing 3. Continue measuring GREEN and BLACK, but now spin the paddlewheel. Your voltage should drop to approximately 6 or 7 volts. a. If good, then the problem is in the readout. b. If not good, then you have either missing magnets form the paddlewheel or the sending unit needs replacing. IV. TR-1E5 - 3 wire transmitter for Nav-5 system. A. Use the same test as for the TR-1. The wires are coordinated in the connectors as follows: 3 PIN CONN. 25 PIN CONN. 1. RED wire pin 1 pin2 2. BLACK wire pin 2 pin 1 3. GREEN wire pin 3 pin 3