Tacho - again!

[imp_nut]

Hi all,

I have searched the forum for this problem, but I think it is a new one...

I have an electronic tacho, known good with points and old-style electronic ign. So I connect it to the MJLJ tach output, and get nothing, so i try the EDIS. My EDIS 4 plug has no hole in between the two coil outputs, so i drill one and connect the tacho to the EDIS, pin 11, the tacho works steady as a rock! BUT with the MJLJ connected (or more specifically the PIP connected) the tacho dies, the only time the needle jumps is whilst cranking. the MJLJ works fine otherwise.

I'm not really an electronics person, and so i'm hesitant about putting an extra diode circuit on the coil outputs, so can anyone think of cure to this fault?

Thanks, Paul.

[brentp]

The tach signal from the MJLJ is a 5v square wave output, so your tach might be expecting a 12v signal.

Pin 11 on the edis module is labeled "clean tach out". Unknown as to why it would stop working if you connected the PIP line to the MJLJ.

What about pin 2, the IDM signal? that fires every time there is an ignition event, it might work for your tach.

Brent

[Ivan]

I seem to have the same problem here with my tacho
When only the edis is connencted the tacho works fine
once you connenct mjlj the tacho dies.
What's up with this?

Ivan

[Ivan]

The signal from the Mjlj tacho is a 5V one, can't this be changed into a 12V output by replacing the Q4 and R10 on the board and connecting it to the 12V input?
The trans and resistor from the tachdriver in the file section maybe?

Ivan

[Ivan]

Please brent can you give me an answer on this 5v to 12v situation
The time is running out to work it out before the race this weekend

Regards Ivan

[brentp]

Ivan,

The tach driver posted in the files section should work for you.. V3 controller will have a 12v output.

[Ivan]

I have tryed it already but no go on tacho yet
I will have a second try tonight
Won't it be possible to change it on the board to 12v outpout?
I am only asking because I don't like to place more boxes with stuf in them than there already are in the car.

I'm no specialist but I think if the trandistor for this output would
be connected to 12V source it would work fine.
Maybe the transistor needs to be replaced and a wirebridge from the 12V source, but this is still not a big cost to change.
Please let me know if I don't know what I am talking about.

regards Ivan