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I'm doing some old school work. I'm wondering where I can get a parade waveform on a GM HEI distributor. I suppose a paddle would supply waveforms but I'm not sure how good they are and I don't have a paddle. A scope on the ignition power lead I suspect would not give a proper waveform because (like a COP coil with the transistor in the coil) you are not connected to the coil. A current probe on the power lead doesn't really give you a reflected secondary waveform for the same reason with the driver being in the distributor. Finally I'm not sure what the tach output of the distributor gives. Can anyone shed some light before I start poking around. I'm looking for good secondary waveforms or reflected secondary (primary) waveforms.
Thanks
Oh sorry I misunderstood your question I thought you just wanted to see what they looked like. Anyways to answer your question to view secondary you would need either a paddle or a secondary clamp I personally chose the paddle because you can use it on cop or ignition wires . You can view primary current with a low amp clamp on either your power or your ground of coil but you won't see the same detail as secondary ignition
I was sort wanting to see reflected secondary waveforms or primary voltage waveforms. Not current waveforms. What does the tach output give? I presume it's conditioned somehow so it won't look right. Maybe I'll have to cobble together a paddle of some sort. I'm wanting to see the spark line and peak spark voltage (or a reflected version of it). I'm pretty sure paddle waveforms may give you the shape but all that I've seen wander all over the place in amplitude. Maybe I'm wrong.
Other suggestions welcome. Thanks
Unfortunately a primary current waveform isn't going to show me what's going on in the secondary (voltage). I have no doubt the module is working properly so the current waveforms will be ok. I'll have to play around I guess. Maybe make a simple paddle or see what the tach output delivers. Could be it will have what I want because I think it will drive old school tachs which were expecting a reflected secondary waveforms from points etc. (several hundred volts).
Thanks
I discovered by accident that on some ignition systems you can capture primary waveforms by holding the scope + lead in one hand ( - to block ground) and simply holding other hand over but not actually touching a COP coil.
Edit I was using the scope this morning so I did a quick capture using above method ---
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
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Last edit: 8 years 10 months ago by Andy.MacFadyen.
Sage wrote: I tried the Tach output from the stock HEI distributor. It shows primary and reflected secondary waveforms fine. Just thought I'd update the thread.
Thanks for the update I'll give that a try the next time I have an hei in the shop
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