INSIDE A DG NITION

[howardjs]

Malcolm and myself set off for a southern Lakes tour on our way to the CSC gathering at St. Bees, we never made it! (But a really brilliant do).
We were bowling along the A590 when with no warning my engine cut.
My engine is fitted with a DG Nition unit that has been totally reliable for 0ver 14 years.
After much head scratching and to cut a long story short, there was no spark at the plugs. We changed the coil, plugs, plug caps one by one but still no spark. In the end we removed the DG and fitted the standard points and condenser. The timing was set as best we could by eye. A turn of the key and the engine fired and ran moor or less normally.

On returning home after the rest of the great weekend, I removed the back on the DG marked the position of the Hall Effect transistors, re assembled and connected up a coil and plugs. Then with a 12volt bench power supply connected I waved one of the trigger magnets across the marks and low and behold, 2 perfect and powerful sparks. This was repeated several time with the same perfect results.

Here are some photos... Any Ideas
Howard

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[Rob Bryant]

MPS 54 print.pdf

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Hello Howard.
Some of the packing machines I work on use hall effect sensors for 'home' positions of grips.
While the sensor chip itself is reliable, the cable to the PCB has to flex many times an hour, and the multicores are only 0.5mm each.
After (X) years, the strands fracture, and the 12v will drop slightly, causing 'not home' errors.
Pic attached shows the hall sensors at the top of L of pcbs, 1 on one pcb, 2 on other. They are a little more beefy than yours, but could the supply voltage have dropped through a loose connection or heat?
Also, checking the operational temp range, 150 C is max. Considering your sensors are smaller, and possibly less tolerant, could temp have been the issue?

Rob Bryant

[howardjs]

Hello Rob, thanks for the input...
The Hall effect sensors on the DG PCB are SMT so very small. The temperature on that day was quite cold and at that point dry (not so for the rest of the weekend)!
I have tested the setup shown in the photo right down to 6 volts and still produces a good sparks.

However on closer examination the wire strands inside the end on the positive feed wire do look as though "black wire corrosion" could have started. So next I will strip the wire back a little at a time to see how far and how bad the corrosion is.

Update will follow...

Thanks again Howard

[howardjs]

Well!
All wires in fine condition,

However, confession time!
The +ve bullet connector certainly is not! This is covered in perfectly even black oxidisation with a conductivity of virtually zero...

How did I not see this when looking for the fault? Perhaps because we were blocking the muddy entrance to a farmers field with the clock ticking.

Anyway, I have ordered some new 4mm connectors so I will now refit the DG... We will see Howard

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