Smiths Mechanical to Electronic Tachometer conversion -741-

In stock

A Service to convert a Smiths RN tachometer to RVC.

Fits Smiths/Jaeger RN Cable Driven Tachometers

Many tachometers from the early 160s on not marked with the Smiths Logo

such as UK built Fords

Datsun ( built under licence in Japan)



Converts RN tachometers to RVC


This is a service to convert a Smiths mechanical ( cable driven) tachometer to Electronic, using carefuly chosen parts to give a period performance whilst appearing to look identical to the original mechanical tachometer from the front..


You will need to supply us with the original mechanical tachometer and a donor RVI tachometer ( we can supply the donor for a surcharge)


We remove the needle and dial, discard the mechanical movement and replace it with the electronic movement from the RVI tachometer. This requires new mounting holes in the base and a brass conversion plate to relocate the dial mounting thread positions.


We then fit the Spiyda RVI - RVC conversion circuit board to the RVI movement, this gives 4 inputs suitable for a wide variety of triggering such as , coil negative, ECU, hall effect, alternator etc.


Finally we rebuild the needle, removing counterweights, fit the dial, balance the movement and calibrate it for the number of cylinders specified.


We do not paint touch-up or otherwise interfere with the patina of the original, apart from cleaning the glass.


Instructions on installation are included when we send the tachometer back to you.


Note - :   the degrees of rotation of an RVI tachometer are a little less than an RN tachometer, so the very highest rpm will not be reached.


If the mechanical tachometer has a rolled on bezel, there will be a surcharge.

The conversion is negative earth unlesss pecifically requested at time of ordering.

The conversion produces a clockwise tachometer unless specifically requested

If a donor RVI tachometer is not supplied, there will be a surcharge for us supplying the donor movement.




Note, 1

there are now four inputs on the board.

They vary in sensitivity from the very sensitive calibration input, to the much less sensitive high voltage inputs.

to clarify how these are used depending on your set-up

for calibration with an audio signal the low voltage input should be used
if you have a tacho output the low voltage or TTL input should be used.
if you have standard points and coil, or electronic points and coil, one of the high voltage inputs should be used,
if the tachometer does not trigger correctly then it is OK to use the alternate high voltage input.



Note 2

unfortunately a customer recently sent us a tachometer through the post and it was badly damaged...

to protect the unit in transit, first cut out and tape a disc of something stiff (like hardboard or thick plastic) over the front

this will protect the glass ( I recently had a customer send one with an old CD taped over the glass.. ---  perfect  !! )

then wrap the whole thing in bubble wrap and put it in a box no bigger than 350mm x 250mm x 160mm  (UK SPECIFIC)

this is a special exception to the royal mail small parcel sizes..  it makes a big difference to cost..

Insurance is up to you...  personally the hassle of trying to get money out of the post office is more trouble than it is worth..

so I generally go for a signed for service.

If your tachometer is very valuable use a special delivery service, please let us know and we will do the same in return.
Remember to include at least a clue as to who the tacho is from !!   and an indication of how many cylinders for calibration purposes
Note 3

We have included more power supply cleaning up circuitry on this latest version of the board.

Note 4

We have altered the board a little to make it easier for those driving it from the "W" terminal of an alternator. The frequency of pulses is higher than ignition pulses, so there are a couple of places on the board to cut to enable the board to respond correctly, these are detailed in the instructions.



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