Ignition Analyzer?

[Buccaneer]

Frank, I think you just described the circa 1950 "Sun" engine analyzer
in my garage that collects junk and needs dusting occasionally.
I got it 20 years ago as the price was right and I had a 1950 Dodge Meadowbrook
to play with. I was able to get about half the instruments working,
but the coil tester wasn’t one of them. At the time I never thought
it would be useful for anything other that automotive type coils,
but perhaps I’ll try again and see if I can get it working!

Bill, thanks for the "tester" link. If I were working on
cars, I’d want one of those. If I get the gist of it,
it sounds like you compare voltages on the engines
different plug wires, weeding out the bad cylinder.
I suppose it may tell me which cylinder is acting
up on the Johnson, but I’m pretty sure it’s the
bottom one, as that spark plug was running cooler.
I’m coming to the conclusion that a Stevens type
tester that induces the arcing problem or coil
breakdown, which ever may be the case,
would be money better spent.
This Ebay ad explains the tool you mention in
case anyone else is interested…
http://www.ebay.com/itm/Snap-On-MT2700- … 82&vxp=mtr
Thanks!

Prepare to be boarded!

[frankr]

Now THAT looks like a useful tool. And only $35 on e-bay. Of course you will need to understand how things work in order to avoid false conclusions. I’d have one if I were doing service work.

[Tom]

Here’s a little more information. Your mileage…, my two cents…, and all the other caveats apply:

The early Merc-O-Tronic and Stevens testers (like the one in the Johnson service manuals from the ’50’s) had a vibrator tube to generate a series of voltage pulses. These pulses were fed to the primary side of a coil. Wires were attached to the ground and the secondary (or both sides of a dual output coil) and then to a spark gap. With the pulses applied to the primary, sparks should be generated by the secondary. These testers had the added functionality of being able to adjust the amount of current applied to the coil, and a meter to read the amperage. Each coil has a current rating at which it should work, so you dialed to the lowest current setting at which the coil fired. If the value was at or below the specified value, great. If it was a lot more, the indication was that the coil could be on its way out. The coil specs were listed in the manual that came with the unit, and specified manufacturer and model number of the motor and/or the coil.

These testers also had a 110 V circuit for testing condensers. Some condenser testers will tell you the capacitance of a condenser, some will tell you leakage. These can be useful for some applications, but not necessarily for magneto diagnostics. The most useful test is to apply a high voltage across the condenser and measure the leakage. These testers had a neon tube that flashed when the condenser discharged. If it flashed fast, condenser was bad. If it stayed on, condenser was bad. If it flashed slowly, the condenser was probably OK. The difference between what the Merc-O-Tronic and Stevens testers did, and what many testers do today, is the voltage applied to the condenser. They really need to be challenged at higher voltages than the ones generated in a $15 tester.

Later models had electronic circuits to generate the pulses, since the vibrator tubes had points inside, which tend to corrode. I’ve brought back a handful of the vibrator tubes by opening them up, cleaning the points, adding some desiccant, and sealing them back up.

The Merc-O-Tronic had a neat feature, a separate probe for measuring voltage leaking from a coil. This was a grounded probe, and you passed the tip near various locations where secondary voltage might be leaking. It could find problems with insulation of the coil, the wires, or any part that could be a problem, like the insulators in the early Eisemann mags and the Johnson alternate twins that fire from one coil. I guess you could do the same thing with your finger if you held the Stevens unit in your other hand, although this would not be recommended practice.

Another way to generate the pulses is to put the primary of the coil to be tested in series with the primary of a Model T coil and a 6 volt battery. The primary voltage of the Model T coils is switched on and off as its points open and close. Since the coil to be tested is in series with the Model T primary, that one is getting switched on and off too. The problem with this method is that you can’t vary the current below the operating current of the Model T coil. But just seeing if the coil under test can generate spark is usually enough. You need to set up a gap for the Model T coil secondary, too, so you don’t burn that out.

If you have a Model T coil set up to test coils, and you want just a decent condenser tester, look into an old Heathkit C-2 or C-3 condenser tester (or the equivalent Knight, PACO, or EICO capacitance bridge testers. They measure capacitance and test leakage at high voltages. My re-capped C-2 is just about bullet proof, and the magic eye tube is pretty cool. Don’t buy the ones that say "In-Circuit" testers, those are a different animal.

T

[jeff-register]

Glad to see someone using Super corona Dope, See it is a good thing! A guy can buy 1000/1 Div probes for the dig meter to measure voltage, Used them with neon testing.
Always wanted to connect my O- scope idling close to shore but a genny, power conditioner & scope might be a little much in a 12 footer.
Use power & measure every step during assembly & sometimes stuff still gets missed. Know the theory of the assembly & pay attention to detale.
Jeff

[billw]

"Bill, thanks for the "tester" link. If I were working on
cars, I’d want one of those. If I get the gist of it,
it sounds like you compare voltages on the engines
different plug wires, weeding out the bad cylinder.
I suppose it may tell me which cylinder is acting
up on the Johnson, but I’m pretty sure it’s the
bottom one, as that spark plug was running cooler.
I’m coming to the conclusion that a Stevens type
tester that induces the arcing problem or coil
breakdown, which ever may be the case,
would be money better spent.
This Ebay ad explains the tool you mention in
case anyone else is interested…
http://www.ebay.com/itm/Snap-On-MT2700- … 82&vxp=mtr
Thanks!"

Well, I use it on outboards all the time. As long as the engine is running, it will tell you something…For instance, if your bottom cylinder is fouled, it would probably read around 2K, even though it’s not even firing. Normally you would see around 6-7K and if it were lean, it would be higher still. At any rate, even with just two cylinders, you would see an obvious difference if one was running and one wasn’t.

Long live American manufacturing!

[phil-b]

I’ve wondered if a known good coil could be used as a "step-down" transformer to measure spark voltage (would need to be calibrated)

[Buccaneer]

Tom, Thanks for your "in-depth" report on the Stevens, Merctronic
and Model T Coils! There’s a lot to digest there. I remember in the
past reading information cautioning against applying 12 volt battery
voltage to outboard coils, in fear of burning them out, and believe
it was suggested to use a 9v flashlight battery on the primary
to induce spark.
I would have to look at a Model T coil again to even remember how
they’re designed, and what’s considered the primary connection, etc., and
how one would utilize a Model T coil in series to test an outboard coil.
Can’t for the life of me remember at the moment what the Model T
had for a timing device to operate the four coils as needed.
I looked briefly at my circa 1950 SUN automotive test center today,
and noted it had three components for testing coils. The current meter?,
the distributor unit with cam and points, and another meter…….
can’t remember what it said.
Am anxious to get back to the HD-15 magneto soon and see
if the problem can be determined.
Thanks for all the replies!

Prepare to be boarded!

[outbdnut2]

quote Jeff Register:

Glad to see someone using Super corona Dope, See it is a good thing! .
Jeff

Is that Corona Dope still available??!! That brings back memories! I haven’t seen that stuff since my days in the TV repair shop back in the 1960s! I would use it if there was a high voltage corona leak in the high voltage "flyback" circuit to the side of the picture tube.
Dave

[Buccaneer]

I played a little with the old, circa 1950 Sun "Master Motor Test Center"
today, seeing if I could get the coil test portion of it useable.
I don’t think it’s suited for outboard coils for some of the test
mentioned in the manual, but perhaps for some of the test it
would work. I could not get the meter calibrated / zero’d out
as it suggest before starting the test.
The unit consist of three components, one has a analog meter,
showing "milliampers", "Bad / Good" range, "ohms", etc.
The second is the "breaker" unit, with points and cam.
The third has the test selection knobs, "Coil set regulator",
"Dwell-Ohm regulation", and a selector dial to select….
"Milliamps, "Coil Set", "Coil Test", "Dwell Ohm", and "Coil Heat".

This is an old "automotive" test center, and some of the coil
test mentions "turning on the ignition key"…… can’t
find one on my outboards 🙂
It was fun to hear the cam and points clicking and clacking though!

Prepare to be boarded!

[Author]

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