how to connect a 2.5 jack -- sensor coil

[akvoyager]

Dear forum users,
Could someone tell me whether the jack socket connectors in the PM3 monitor are connected to the plus and minus of the power supply ? There are three connectors and someone soldered the jack socket incorrectly. I don't know where the sensor coil wires (white, black, red) should be connected on the PCB.

Best regards
Artur Kalbarczyk

[Carl Watts]

2.5mm TACH connector.

Model D/E
Stereo - 3 wire
White - tip
Red-centre
Black-base

Model C
Mono-2 wire
Works either way around, technically they wire it for positive pulses.

Note if you purchase another moulded cable and connector the connections can change.

Personally I wouldn't bother trying to fix a cable anymore, just replace the whole pickup, especially if you have the older single yellow coil version just bin it and replace the whole thing including the plastic holder with the newer twin coil design.

Hopefully yours is not like the worst one I have ever had to repair, they drilled a hole in the PM3 case, cut the connector off and tried to direct solder the cable to the socket

[JaapvanE]

For completeness:
Model D/E
Stereo - 3 wire
White - tip - Signal, 15V sinoid
Red-centre - 15V rectified from coil to PM (the coil powers the PM)
Black-base - Ground

But as Carl said, just replace the damaged sensor. It is easier and might prevent damaging a working PM.

[akvoyager]

Thanks a lot for answer!

By the way, two questions more:

1. Carl Watts, do You have any photos regarding Your repair: "they drilled a hole in the PM3 case, cut the connector off and tried to direct solder the cable to the socket".
I have to fix connector in PM3, it means solder connector properly. My sensor looks good, I think. PM3 socket reguires fixing.

2. JaapvanE, why does sensor produce two signals, instead pulses like in the old bike computers (magnet on wheel, sensor on bike fork)
"White - tip - Signal, 15V sinoid
Red-centre - 15V rectified from coil to PM (the coil powers the PM)"

Sincerely Artur Kalbarczyk

[JaapvanE]

2. JaapvanE, why does sensor produce two signals, instead pulses like in the old bike computers (magnet on wheel, sensor on bike fork)
"White - tip - Signal, 15V sinoid
Red-centre - 15V rectified from coil to PM (the coil powers the PM)"

The sinoid is used for measuring flywheel speed, which drives all metrics the PM presents. The rectified signal is used as power for the PM5, so when you row, it won't depend on the batteries.

[Carl Watts]

The TACH socket is surface mount on the board so its either visibly cracked through the plastic case or the soldering to the board is broken and the socket moves making an intermittent connection. Generally if the soldering is good, there is no problem with the socket.

90% of the time the 90 degree 3.5mm stereo connector has a wire fractured inside. This is a fairly common problem. I have never had a component failure on the TACH pickup, its always the cable.

[akvoyager]

JaapvanE, this solution makes sense and is simple and smart.

Carl Watts, thank You for opinion. This will allow me to narrow down the suspects

We can close the thread, thank You for help !

[akvoyager]

However, one more and last question. My guess is that someone soldered the socket incorrectly. Do You know, which colour of sensor-coil-cable (white, red, black) go to the orange marked soldering pads ?

Below link to the picture:
https://drive.google.com/file/d/1PeeKW4 ... sp=sharing

Artur Kalbarczyk