SW 990B tach and 970 transmitter?

dec31 · #1 01-30-2007, 04:29 PM

I was wondering if anyone out there can tell me what exactly the function is of the 970 transmitter block for the SW 990B tach. What does this unit do. I did call SW directly and no one there could tell me, the company has changed hands so many time the info is no longer available

. I would appreciate the assistance
thanks Chris

68l30 · #2 01-30-2007, 05:06 PM

FYI....990B is the transmitter......970 is the tach...

Steve

**SuperNovaSS** · #3 01-30-2007, 07:37 PM

Chris,

I believe all it does is reduces the voltage to the tach. I opened one up at one point and if memory serves me correctly the only thing inside is a resistor on the 12V area.

Jason

**Steve Shauger** · #4 01-30-2007, 08:10 PM

I am not sure, but the transmitter probably conditions the pulses coming from the distributor, and integrates them. Basically the # of pulses for a period of time represent a voltage, more pulses the higher the corresponding voltage is. The meter movement is a voltmeter calibrated to convert voltage to a corresponding RPM's.

dec31 · #5 02-02-2007, 03:14 PM

Thanks for the input guys. May have to make a trip to a electronics shop and have them test it to figure out what it really does for sure.
Thanks again for your help
Chris

Dedicated to the Promotion and Preservation of American Muscle Cars, Dealer built Supercars and COPO cars.