Dancing Dizzy King Lead waveform - Help!

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Dancing Dizzy King Lead waveform - Help!

Postby FioranoCars » Tue Aug 01, 2017 1:24 pm

These 2 captures are both from the same vehicle, a few weeks apart, pre and post Dizzy rebuild.
Excuse the channel limit displaying at 10kv, but fixing that was not as important as stabilising the signal ...

I have moved the earth location a few times, engine block, chassis and finally battery terminal (where the other channels were earthed), but the dancing continued.

I can't think of anything else that has changed since the previous capture was taken, both on same 4425 scope, both had laptop on battery power, no chargers connected.

Pre-Rebuild
king lead - stable enough.png
Relatively Stable pattern on King lead

Post-Rebuild
king lead - NOT stable.png
UnStable Dancing King Lead


What's up :oops: , what have I overlooked:?:

First it looked to run in 4's but looking over several buffers it's fairly random ...

Secondary spark captures on the HT leads are all good and stable, so are injector voltages (within same capture), it's just the King lead.

I have noticed that others who have posted Dizzy king lead traces seem to supper to some degree or another, but some are perfectly stable. Earth was my first thought, and I've done all I can think of, back to battery negative. Face black from dust on coal face, no doubt will turn red when someone points out the obvious snafu I've made :? :?

Thanks
Richard
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Re: Dancing Dizzy King Lead waveform - Help!

Postby Autonerdz » Tue Aug 01, 2017 6:00 pm

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Re: Dancing Dizzy King Lead waveform - Help!

Postby FioranoCars » Tue Aug 01, 2017 9:43 pm

Thanks Tom

I have seen the single slow earth, but this is more extreme and makes analysis of the coil almost impossible ...

While the phenomena seems to be repeatable at the time it occurred (and unable to be cured), I was doing more tests today, and the leads were still attached, although the scope had been disconnected and laptop unplugged, basically it was all the same. Today the signal was steady (not perfect but not dancing like yesterday):
king lead - stable again.png
Back to Stable

I know that inductance can have issues, but there must be some aspect influencing this extreme behaviour?

The pickup leads are the same (not rotated), the king pickup position was changed yesterday many times on the unstable readings from coil to dizzy ends and the middle. Today it was fine first go. The only thing I changed was adding a jumper lead to the engine from Battery negative terminal, but removing it did not revert to dancing ... The starting settings were the last file from yesterday, so nothing changed there ...

It's hard to believe there is not some aspect (leads routing, scope location (yesterday hanging, today on front wing, but in rubber protector), that is cause/effect. It's hard to believe that such a radical issue cannot be overcome, yet disappears on its own a day later?

Should there be a redesign to the pickup to improve stability? It's solid state stuff, so surely can't be a failing test lead?

I hope tomorrow does not return to dancing, as need to take some dwell readings at 1,500 and 3,000 rpm, and rather not be fighting noise (yes I know a DMM can do this, I'm just curious if there is any differential between the two).

Thanks
Richard
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