VR Circuit Trouble

[EmileS]

Hi.

I've recently finished assembling a V3.0 board with an MS II processor and I'm running v2.684 firmware.

I'm having trouble with my tach signal, when I crank the engine I get an rmp signal of 6000 – 8000. I'm currently using a Bosch VR sensor with a 60-2 wheel on the crank.

I've tried adjusting R52, but the signal just changes to 70+ rpm, there's no transition, it goes directly from the first rpm signal of 6000 down to 70.

When I adjust R56 the time it takes to change from 0 rpm to 7000 rpm seems to become instantaneous.

I've checked all the components and I've checked for dry solder joints but everything seems to be fine.

Also, during cranking I measure a voltage across the VR sensor of 1.8V. Unfortunately I don't own an oscilloscope so I cannot get an indication of the signal from the VR sensor

I haven't tried to connect a resistor from VR ground to R56's wiper, as I'm not to sure if it will solve my problem. Also, everything seems to be fine when I use the stim.

Can anyone give me advice on what I should do.

Thanks.