Tach signal from rectifier

[Texasmark]

Just acquired a 2002 115 2 stroke. Tach inop.

Checked voltage and ground at tach and ok.

Ohmed grey wire from tach to bayonet connector inside engine adjacent to rectifier-regulator module....continuity ok...did find connection to appear corroded....shined it up. Haven't run engine since so don't know if that was it.

Voltage output from rect-regl ok.

If voltage is ok, could the tach output still be bad.....do not have schematic of reg-rect? I understand that the tach signal is just picking off (sampling) the rectified half waves from the rectifier section and the tach counts the peaks....if so, what is there to fail on that?

Do you need an oscilloscope or a fancy multimeter with a video display to read the signal? If DCV on a multimeter how much voltage? Probably a voltage divider inside module to cut the voltage to something in the digital range.....5v?????

Manual is on the way so no help there yet.

Thanks,
Mark

 

[Texasmark]

Just got my service manual today. If anybody is interested the manual says it needs to be greater than 2 VDC at the Signal input to the tach. Also it says it's simply the rectified sine waves coming from the 6 coil charging stator. No reference to whether or not it is fed through a voltage divider network to drop it to a value usable in the tach....probably if there is one and probably is, it's in the tach itself since that's where the signal processing takes place and that's where the size of the signal would matter especially when it can get to 16v coming right off the rectifier diodes.