16 replies to this topic

[Spider]

 

Those tachos need a 12 V supply. It's an RCV type of Tacho. I have found inside them there is a pot for calibrating, but if opening it up for adjustment, I'd suggest replacing all the Electrolytic Capacitors too (there's only one or 2 of them) as they'd likely be on their last legs by now.

You can calibrate the unit yourself, find yourself a 12V AC Plugpak (or transformer), connect that between Earth and the Pulse Input Terminal. In the UK, it should read 3000 RPM and in the US, 3600 RPM.

Tried that but don't get any reading.....googling suggests this needs to be done with the coil or a bulb wired into the circuit

 

 

I've only ever had trouble with that when the Tachos been duff, but nothing to loose by trying again with a coil or bulb as has been suggested, also try with the AC Source between +ve and the Pulse Input.

[Vanman20]

We have success.
Got that test circuit working with a bulb,was showing 2,500 rpm.
There is an adjuster but it's not a screw , it's the white arm in the picture below.
Adjusted that to 3000rpm and now it not only seems to work reasonably accurately it also starts reading without me having to tap the glass