<div dir="ltr">Thanks very much, Mark. Regarding the Snap-on 'scope, yes, absolutely, it was automotive-specific. Here's a link to one for sale on eBay just to give you an idea:<div><br></div><div><a href="https://www.ebay.com/c/1104491855">https://www.ebay.com/c/1104491855</a><br></div><div><br></div><div>SO</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, May 13, 2020 at 8:11 AM Mark Johnson <<a href="mailto:markjohnson100@centurylink.net">markjohnson100@centurylink.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<p>Steve:</p>
<p>Great explanation of LRC circuits...I know (or used to know) most
of this, but your explanation is one of the best I've ever seen. <br>
</p>
<p>I didn't know Snap-On ever sold oscilloscopes - presumably for
diagnosis of automotive ignitions and electrical systems?</p>
<p>With all the GHz-range clocking of modern personal computers, a
knowledge of analog and RF is still very important. At 3 GHz, a
1-inch trace on a circuit board is an antenna!<br>
</p>
<p>Mark Johnson (WB9QLR)</p>
<p>Columbia MO</p>
<p><br>
</p>
<div>On 5/13/2020 6:58 AM, Stephen Offiler
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Glad you mentioned resonance, Carl. This is the next level
of the discussion that I purposely avoided in my previous
comments. With points open, it's a LRC circuit. L is the
inductance of the coil primary; R is the small resistance of
the primary; and C of course is the capacitance of the
condenser. At initial points opening (only open a tiny amount
thus far) a voltage spike comes out of the primary and is
absorbed by the condenser. This discharges back thru the coil
primary in a "ringing" or resonance fashion, and some energy
is dissipated by the resistance. The "ringing" reverses
again, several times, with an exponentially decreasing
amplitude as energy is dissipated. It happens (or should
happen, if the circuit is properly balanced, as you mentioned)
very rapidly. The points re-closing will dead-short the
condenser but by now there's very little energy left to be
dissipated.</div>
<div><br>
</div>
<div>I have some neat oscilloscope plots of this phenomenon
somewhere... oh, just realized where they are: in the
instruction manual for an old Snap-on "Counsellor"
oscilloscope from the 1980's. It happens to be at work right
now. I wonder if I can remember to scan some and send them
along.</div>
<div><br>
</div>
<div>What is really fascinating is that the points-and-condenser
ignition was developed, as far as I know, before the invention
of the oscilloscope. Early electrical engineers had a strong
intuition for analog circuits.</div>
<div><br>
</div>
<div>SO</div>
<div><br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, May 12, 2020 at 7:19
PM <<a href="mailto:szabelski@wildblue.net" target="_blank">szabelski@wildblue.net</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">I agree that the
condenser is wired across the points, and it helps prevent
burning of the contacts by helping to suppress the arc when
the points open. But a condenser can only store so much
energy and must be discharged at some point, it can’t absorb
energy forever. The condenser has to be discharged before
the next opening of the points or it can’t absorb any more
energy and help suppress the arc. It becomes discharged
when the points close again. That is also when the plug is
firing, so that stored energy goes into the spark. The
condenser and coil also form a resonant circuit which is
what is needed to try to have a stable system since the
energy from the coil rises and falls as the energy is
created and released.<br>
<br>
That is why there are as many different condensers available
,as there are cools. You need one that properly works with
the coil to absorb the level of energy developed by the
coil. If it can’t absorb enough, points burn. You also don’t
have a properly balanced resonant circuit.<br>
<br>
Carl<br>
----- Original Message -----<br>
From: Stephen Offiler <<a href="mailto:soffiler@gmail.com" target="_blank">soffiler@gmail.com</a>><br>
To: Antique Tractor Email Discussion Group <<a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a>><br>
Sent: Tue, 12 May 2020 10:04:58 -0400 (EDT)<br>
Subject: Re: [AT] AT Digest, Vol 28, Issue 7<br>
<br>
Condenser function: it connects across the points, aka in
parallel.<br>
Points are used to switch current through the coil primary.
Coil primary<br>
functions like a big inductor - it stores energy in a
magnetic field, and<br>
it uses that field to supply energy to oppose any change in
current. It<br>
can't win, because the energy gets depleted, but it does
try. As the points<br>
open, that implies a sudden change in current from the
steady DC value to<br>
zero. Inductance responds by trying to keep that current
flowing. It<br>
"piles up" electrons at the opening points which elevates
the voltage<br>
there. It would certainly arc, if the condenser wasn't
there. The<br>
condenser charges up and gives that voltage (that pile of
electrons) a<br>
place to go, thus suppressing the arc and extending the life
of the points<br>
substantially.<br>
<br>
SO<br>
<br>
<br>
On Tue, May 12, 2020 at 9:49 AM <<a href="mailto:szabelski@wildblue.net" target="_blank">szabelski@wildblue.net</a>>
wrote:<br>
<br>
> Steve,<br>
><br>
> The condenser is actually a capacitor, originally
called a condenser<br>
> (probably because a charge condensed internally) and
later called a<br>
> capacitor. There should be no continuity between the
condenser case and the<br>
> pigtail wire. A capacitor is made of two thin sheets of
metal that hold a<br>
> charge until there is a short between the case and the
pigtail. The two<br>
> thin plates are separated by a thin medium that allows
the charge to build<br>
> up to a specified amount. The purpose of the condenser
is to store extra<br>
> energy and give you that little “extra kick” when
discharged.<br>
><br>
> As I said in an earlier post, it is difficult to check
a condenser, it<br>
> takes special equipment. Even if it passes, there is no
guarantee how long<br>
> it will last since the medium that separates the two
plates can fail and<br>
> allow a short between the two plates. The best thing is
to try a different<br>
> condenser. It just has to be one with the same capacity
to store the<br>
> required charge.<br>
><br>
> Carl<br>
><br>
><br>
> ----- Original Message -----<br>
> From: STEVE ALLEN <<a href="mailto:steveallen855@centurytel.net" target="_blank">steveallen855@centurytel.net</a>><br>
> To: <a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a><br>
> Sent: Mon, 11 May 2020 17:39:06 -0400 (EDT)<br>
> Subject: Re: [AT] AT Digest, Vol 28, Issue 7<br>
><br>
><br>
> ----- Original Message -----<br>
> Message: 7<br>
> Date: Sun, 10 May 2020 19:53:23 -0500<br>
> From: Phil Auten <<a href="mailto:pga2@basicisp.net" target="_blank">pga2@basicisp.net</a>><br>
> To: <a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a><br>
> Subject: Re: [AT] Project Updates '49 A, '51 A, and '47
B (STEVE<br>
> ALLEN)<br>
> Message-ID: <<a href="mailto:168f1f90-8d7a-1eef-e95e-28fb0fa7e41b@basicisp.net" target="_blank">168f1f90-8d7a-1eef-e95e-28fb0fa7e41b@basicisp.net</a>><br>
> Content-Type: text/plain; charset=utf-8; format=flowed<br>
><br>
> '49A - If your points are clean and reading .5 ohms
when closed and .7<br>
> ohms with cardboard separating the points, your points
are shorted. With<br>
> the cardboard in, they should read an open circuit, and
.5 ohms when<br>
> closed says your contacts aren't making contact well.
If you took those<br>
> measurements with the points installed, disconnect them
and retest. If<br>
> the points read 0.0 ohms closed and open circuit with
the cardboard in,<br>
> then the problem is elsewhere.<br>
> '49 A: I forgot to mention, if the points measure
correctly outside the<br>
> distributor you may have a bad coil.<br>
><br>
> Phil in TX<br>
><br>
> Phil,<br>
><br>
> Remember that the points set in a Wico X mag is two
separate pieces. If I<br>
> take them off, I can screw them back together and check
for continuity,<br>
> BUT: while mounted in the mag,<br>
> the fixed one is in contact with the case of the mag,
and the other, the<br>
> one that moves, is in contact with the terminal of the
condenser. Now, let<br>
> me speculate here:<br>
> the terminal in the condenser does not touch the case
of the condenser,<br>
> right? So, the two points should not have continuity
because the one is<br>
> connected to the terminal<br>
> and the other is "connected" (through the case) to the
mag case. UNLESS<br>
> there is continuity inside the condenser. I do not
understand condensers<br>
> well at all,<br>
> but *SHOULD there be continuity between the case of the
condenser and the<br>
> terminal of the condenser*?<br>
> If not, that may well be my problem (per Cecil). I
will investigate<br>
> tonight.<br>
><br>
> BTW, I know that the shaft is turning and that the
points are opening and<br>
> closing: I have verified that much by turning the
crank.<br>
><br>
> The "original" Steve Allen<br>
> Who is avoiding the local Menards<br>
><br>
><br>
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