Technical Ignition Condenser problems

Tube car radios used a vibrator, which basically starts and stops the DC current repeatedly. Old tube radios (and guitar amps) operate off alternating current. They use a power transformer to step the voltage up from line voltage (110 back in the day) to typical values from 300 - 500 volts. The transformer works with AC current, because each time the current reverses direction the magnetic field around the iron core collapses, inducing a voltage in the secondary coil. Well, cars operate on direct current, so the current is not reversing direction, so there is no collapse of the magnetic field, and no voltage can be induced. So they added a vibrator to the primary side of the circuit. The vibrator interrupts the DC current repeatedly, which results in a collapse of the magnetic field in the primary coil and induced voltage in the secondary coil. The buffer capacitor is used around the vibrator, and needs to be 1000 - 1600 volts capacity because, yes, the voltage seen is that high, due to the flyback voltage I described above. Even when replacing an old paper cap with a film cap you still need to use a high voltage capacitor in that application.

 

Cool, but my scope probe leads aren't that long!

 

only need about 3 feet to go over a fender...right? or do you have one of those silly rack mount scopes

 

Back in the day, many mechanics never changed condensers because they never went bad. Seems like they cause considerably more problems these days. Same with coils. The only coil I ever had go bad was on a 10 year old Kohler engine on a lawnmower. I replaced the coil with one that supposedly was for use on a 12 volt system without a ballast resistor and it only lasted for 18 hours.

 

In Squirrel's schematic, I like how D1, D2, D3, & D4 go 'round and 'round and 'round - it's a wonder any juice ever gets to the coil! Ain't electronics fun?
My '60 T-bird mild custom had a condenser go (intermittently) bad right before a trip to a Goodguys event. It acted just like my other car did when rust in the fuel tank was intermittently clogging the screen on the pickup. I looked at everything from the fuel tank to the spark plugs before I remembered having a condenser cause the same symptoms on a previous car. But two "new" ones I bought from the local chain store were also bad (now I know why, thanks to this thread). The 3rd was a charm, Standard Ignition Parts from a Carquest store, ran fine from then on.

 

btw on the Mark Ten B schematic, the DIST connection goes to the points.

 

It's mounted above my bench, underneath a shelf. I have the scope, DMM and a signal generator all mounted up like that, side by side. My electronics work is all done on the bench underneath them, and I can't get a car anywhere close.

 

My brother has a pretty tall equipment rack, with his atomic Nixie clock on top, and a bunch of other gear including a scope, power supplies, signal generator, spectrum analyzer, etc. I need portable stuff.

 

I was wondering where they were. So then where is the high voltage discharge? Is it N?

 

High voltage ends up across -COIL and +COIL.

 

OK, well I'll admit it. I'm lost....

 

me too!

 

The basic idea is that the two transistors, transformer, and bridge rectifier on the left are a DC-DC switching power supply, that provides a high voltage to charge one of the capacitors...which is switched by the SCR....but I get lost in all the signal shaping stuff.

 

Speaking of coils, how often did they typically go bad back in the day? It's definitely not unheard of, but I've never had a bad one as far as I know.

Modern rigs have COP "coil on plug" i.e. each cylinder gets its own individual coil, and I guess, no more spark plug wires. OK. But I'm reading all these guys having problems. The OEM coils are 50 bucks (or better) a pop, and they are having problems. Lots of problems. One workaround is (you guessed it) el-cheapo parts for a fraction of the cost.

BUT, it seems to me dividing up coil duties to 1 ea. per cylinder should increase reliability? Just seems strange that autos used a single coil for 100 years but the replacement is less reliable?

 

Over the years, I remember one coil going bad...when I was a teenager, I got to fix the family cars, which learned me a lot. One thing I fixed was the 67 plymouth wagon, 2bbl 383, it got to where it would die going around a corner. noticed it had some oil leaking out of the coil (which was mounted on it's side in that car). replaced the coil, fixed the problem.

I've seen modern aftermarket race type coils cause problems.

 

I taught ignition for Lincoln Tech for quite a few years. My class was 5 weeks long at 4 hours per day. I used to go to the Sears repair center ( large auto shop in a shopping center in Indy) as i had some friends working there. They gave ne a 55 gallon drum full of replaced ignition coils. We took them to class and i handed out one to each student to clean up, test on sun tester look up the factory specs etc. Maybe there was 2 or 3 bad ones in a 55 gallon drum!
All were replaced on being bad ??????????????

 

I use a vertex magneto condenser from Taylor cable in my dual point distributor...its a little bigger that the stock one but a very quality unit...had nothing but issues with new and NOS ones that never worked or only worked a short time... never had a problem with the mag condensor....might be the same one Bubba uses...

 

Saving for later reference as I've been the object of embarrassment in Ventura Ca. during Primer National's due to such issue's posted here.

 

We do use a Vertex Mag condensor that my friend has made for his business ( Mag Tech) in Indianapolis.
Good quality unit , never seen a defective one.......

 

Sounds like your friends were either incompetent or crooks.

 

Ha-Ha love that video, educational,and funny 1!
hey Jim, EVERY TIME we DYNO test an engine with points ignition, it starts popping and carrying on at around 4500 no matter how many set of points and condensers we use, NAPA, Bluestreak,DELCO, etc.. No exceptions. all are a miserable mess .Then we trigger the MSD box with the points and it will run then.. But have not found any point ignitions to run past 4500 under the load of the engine DYNO.
That really makes you a bigger hero, drag week with points !! wow you're the real deal !

 

sadly all those "defective" coils were replaced, because all the younger new "technicians", are trained to read the trouble codes from the computer in the car. The computer can only point you to the area of a problem, then you need to verify the exact cause of said problem, these new "techs" do not have enough automotive experience to go any further than what the computer told them. At least that was my experience working alongside these "techs", and one of the biggest reasons I retired from automotive repair work, the dealerships and larger auto repair shops prefer to change parts rather than repair vehicles.

 

Sometimes (Well, so I have read) a coil will work when cold but become intermittent or fail when hot.

A coil with a few shorted turns in the secondary can be really a bitch to find (without a scope maybe) it will spark and the engine will run but the spark is severely attenuated in terms of spark duration. Something to be said for making baseline measurements and recording them. In this case a coil might be approx. 1 ohm primary (these hardly ever fail) and the secondary will be 8 to 10,000 ohms, but unless you've measured prior there's no way to tell particularly and it might still be in spec. Maybe measure a new coil and jot it down before installation.

That way later on if something is out of line it will be easier to find. Knowing a particular engine's baseline vacuum is good for example too. A single low tire might be missed but it won't be to a vacuum gauge going down the highway.

Ignition condensers can fail the same way, they work OK until hot.

 

[QUOTE="BJR, post: 11471400, member: 5372"]Sounds like your friends were either incompetent or crooks.[/QUOTE]
Lets just say "they didnt know" there are still shops out there that try to do a great job and just for one reason or another, "just dont know"....
Whats the old saying ???? You dont know what you dont know???

They also had a huge stack of defective batterys, none of which said Sears on them??

 

It could happen! More likely to win the lottery and get hit by a meteorite on the same day but, it could happen.

 

After reading everything in this thread. What then is the RPM limit's for a points distributor triggered by an MSD box vs a Magneto (providing an automotive mag has points like a lawn mower) ? I ask because what exactly is holding back RPM's then ? The condensor or the point's ?

 

with points (no MSD), it's the limited amount of power (which is voltage times current) you can get into each spark.. As the rpm goes up, the time to "charge" the coil decreases. Using an MSD box helps by increasing the voltage provided to the primary side of the coil. A magneto provides roughly the same amount of power per engine revolution, regardless of RPM.

at least that's my understanding.

points start to bounce at higher rpm, so either way you have to deal with this as rpm increases.

 

I have nothing to add; except I wish there was a way I could learn auto electrics without getting electrocuted or frying components. A bit of an exaggeration, but you know what I mean. Is there a comprehensive and easy to understand book out there for this kind of thing?

 

Google is your friend. I'm sure there are lot's of websites out there with basic auto electric info. Auto electrics are pretty simple, though it probably helps to have a basic understanding of electricity.