 $29 Oscilloscope, always wanted to see a spark |
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| worn |
 Jul 19 2017, 10:28 AM
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#1
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can't remember  Group: Members Posts: 3,144 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest 
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I have had squirrelly ignition problems with the rebuilt 911 and the 2056 teener. In both cases a key problem was that a new part was assumed to be a functioning part. This is electrics, so I should have known better. Having taken LC circuits in physics 40 years ago I figure I know how to push electrons. Again not necessarily so.
At any rate I found an Amazon deal on a oscilloscope kit for $29 shipped. Except the price includes an extra $4 to have it shipped already assembled. I am too old for surface mount soldering (IMG:style_emoticons/default/blink.gif) . And here is the spark trace from the 914:  To get this I made a 1000-1 capacitance probe with a piece of copper pipe and a couple caps and resistors I had lying around. I followed the basic ideas here. https://www.princeton.edu/ssp/tiger_cub/lib...n_waveforms.pdf The basic idea is to put a slit piece of copper tubing around the plug wire with a clothespin and link that to a 1 microfarad capacitor assuming that the tubing is around a picofarad. I used what I had in the bins. At any rate I always wanted to see what the spark was like and hope to be able to use this for better tuning. Someday. I already know that the waveforms aren't even. Haven't spent enough effort to determine how consistent this is - may be a limitation of the number of places available on the screen and thus limited resolution. |
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| McMark |
Jul 19 2017, 11:35 AM
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914 Freak! Group: Retired Admin Posts: 20,179 Joined: 13-March 03 From: Grand Rapids, MI Member No.: 419 Region Association: None |
I've always wanted to get more knowledgable about this stuff too. Watching along and hoping for some additional insights from others. (IMG:style_emoticons/default/popcorn[1].gif)
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| Elliot Cannon |
Jul 19 2017, 02:40 PM
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#3
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914 Guru Group: Retired Members Posts: 8,487 Joined: 29-December 06 From: Paso Robles Ca. (Central coast) Member No.: 7,407 Region Association: None 
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That looks like my last EKG. (IMG:style_emoticons/default/biggrin.gif)
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| worn |
Jul 19 2017, 05:50 PM
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#4
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can't remember Group: Members Posts: 3,144 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(Elliot Cannon @ Jul 19 2017, 12:40 PM)  You know, it does remind one of the keg. Which spell check chose to spell as KEG. The spark looks like the QRS complex, which seems appropriate. Hope the ticker is as it should be Elliot (IMG:style_emoticons/default/piratenanner.gif) |
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| crash914 |
Jul 19 2017, 07:56 PM
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#5
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its a mystery to me Group: Members Posts: 1,826 Joined: 17-March 03 From: Marriottsville, MD Member No.: 434 Region Association: MidAtlantic Region |
looks like a coil or dwell issue. Not consistent.
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| worn |
Jul 20 2017, 09:51 AM
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#6
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can't remember Group: Members Posts: 3,144 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(crash914 @ Jul 19 2017, 05:56 PM) looks like a coil or dwell issue. Not consistent. Well, the dwell hasn't been set - this was done with a feeler gauge. Also, I am not sure how well the scope works - $29 isn't going to buy you a ton of resolution. I am new to all of this. Anyone with experience reading these things want to chime in? I am particularly interested in finding coil problems as they develop. The trace is with a new Bosch blue coil straight out of the box from Brazil. |
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| worn |
Jul 20 2017, 09:51 AM
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#7
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can't remember Group: Members Posts: 3,144 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest
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QUOTE(worn @ Jul 19 2017, 03:50 PM) QUOTE(Elliot Cannon @ Jul 19 2017, 12:40 PM) You know, it does remind one of the keg. Which spell check chose to spell as KEG. The spark looks like the QRS complex, which seems appropriate. Hope the ticker is as it should be Elliot (IMG:style_emoticons/default/piratenanner.gif) Dammit - I retyped EKG twice! |
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