converting a smiths rvi rev counter to negative earth

[underkut]

As headline says.
I have a 4inch smith rvi2423 from my 1300gt that is currently positive earth that i am chaning to negative.
I see from articles that these can be polarity swapped.
Any one know how.?

[surfblue63]

A quick internet search found these two links that might help

http://www.mgexp.com/article/neg-convert.html

http://mgaguru.com/mgtech/dash/dt201.htm

[underkut]

I had seen these but they are for the slightly earlier version.
I am sure the procedure would be the same but i am having difficulty identifying the componants.
My one does not have the simple earth connection like the earlier ones.
It seems that most of the web details are for the earlier version although i have found a conversion pcb on ebay that may be the way to go.
If anyone does have the solution i would welcome it unless anyone has a negative earth rev counter from a 1300gt??

[dklawson]

If I may offer a different suggestion than what you may have found on eBay.

Board member Chris sells a conversion board on his Spiyda Design web site. The board will convert the RVI tach to what is effectively a later negative earth RVC type. If you use his board it will address both the polarity conversion and allow you to use the tach with an electronic ignition should you decide to fit one. The RVI tachs are generally unhappy and won't work with electronic ignitions.

https://www.spiyda.com/magento/index.ph ... board.html

[underkut]

How spooky.
That is the very person whom i have ordered one from for £41.00 inc delivery.
I shall update on here when completed and installed.
Thank you.

[rich@minispares.com]

You can get neg earth rvi rev counters, I have one in the er cooper s

It works fine, though some on has been into to neatly paint the red mark at 6000 rpm white


That means I can rev it another 1000 rpm right?

[underkut]

Well i said i would give an update once the modification was done so.
Ordered the item last sunday from Spiyda as mentioned.
This turned up on tuesday.
On wednesday i carried out the conversion and with the help of his youtube videos thought i had it sorted but could not get any reading.
On Friday i brought the battery into the house and with the supplied calibration lead plugged the lead into my pc where i had already downloaded the calibration frequency.
It worked fine so performed calibration and put the unit together.
By now i had already worked out that the wiring would have to be altered to suit a RVC type but in the back of my mind i had a oil filter light in the car so was going to adopt the cable but when i checked (although i have the light i have no sensor or cable ????)
I therfore had to run a cable ( infact i run a 4 core flex due to the secondry insulation and some spare cores should i need them ) to pick up the negative side of the coil
I was so tempted to connect the rev counter up under the bonnet to prove it worked but i thought no. One more bench test first. The bloody thing did not work!!!!
I assumed a poor earth through the case so opened it back up and linked the guts to the casing with an earth link and hey presto.
I then was confident enough to fit to the dashand remembering to link the old loop cables together i put it all back together.
Then the big test turned the engine over and while cranking over the rev counter bounced about but sat around 7000 revs .Until the engine fired up and then there they were
A perfect steady reading.
I am one happy man

[dklawson]

Excellent !

However, I am sorry it was a bumpy road getting to the converted working tach.