XJ12; 1979 triggerboard with Hall and primary of coil
 

Hello
is a Pre HE motor;
Can anyone explain whats happening with the signal coming from the trigger board in the distributor (red wire). Where is the signal 600Khz) decoded and how can it make the primary of the coil circuit closing. Does anyone has a diagram of whats happening between the red wire and the coil primary.

Not quite sure what you're trying to achieve, but assuming you have a 4 wire trigger board (you mentioned hall effect, which means 4 wire) it's likely the red wire is the 12V ignition wire, and most people connect this to the coil primary terminal. It is a better suggestion to connect it to a clean ignition supply, ideally through a standalone relay to make sure you are getting a nice, clean 12V to the trigger board.

At this moment I only try to understand. The signal on the red wire is a modulated 600KhZ signal. How can this provoke the primary to be closed and (at firing moment) to be cut off.

A few things concern me here.

The trigger board has NOTHING to do with the coil, or the ignition system.

The trigger board, eithyer 3 wire, or 4 wire, is for teh Injection System only.

The 2 systems, fuel and ignition, do not "talk" to each other.

The only relationship, and the WRONG one, is the 4th wire being connected to the +ve terminal of the ignition coil, which only has ABOUT 7volts avaialble in the running mode.

As said,that 4th wire (and I forget the colour after all these years, but Red sounds about right), MUST be connected to a GOOD 12v Ignition supply.

If I understand it well: the red wire with the signal from the pick up goes to the ignit. amp and on the other hand the output of the triggerboard goes to the D jetronic?

The 4 wire board requires a 12v Ign power supply, thats it. This is done via that 4th wire.

The 4th wire is a SUPPLY wire, NOT an outgoing wire.

Where people get that supply from has reeked havoc over the years, and a stand alone relay to do this task is what I have done with every PreHE I have worked on, and surprise, surprise, the engine runs as designed.

The old 3 wire, reed switch board, had no 4th wire or power supply, the magnet in the heel of the rotor simply triggered the imbedded switches at each end of the board. Unreliable was an understatement, and the 4 wire board was introduced very early.

Again, neither board has ANY influence on the ignition system, and the Ignition System has NO inlfuence on the trigger board.

The rotors have a different shaped magnet for each board, and I have NO idea why. My understanding is a magnet is a magnet, but there is a rectangular magnet and a round magnet, and I do not remember which goes with which board, and what, if any, difference it would make.

Thanks for yr answ., Grant.
Maybe some magnets have more focused magnetic field lines?

This may be of interest

https://www.jaguarforums.com/forum/x...5/#post1402353