The Stovebolt Site Forums The Shop Area The Electrical Bay Ign Coil Bracket

This won't change the world, but it's always puzzled me ... what's the purpose of the raised cut-out on an ignition coil bracket?
'54 235 engine pic
After market bracket pic

Thanks,

Hey, I've always wondered that too!

That was to install a capacitor to eliminate radio noise.

Radio noise suppressor, sometimes called a condenser/condensor

Installation instructions - figure 60, coil condenser, Radio Noise Suppression Equipment. The Wheel Bearing Static Collectors and the Distributor Suppressor are harder to find.

Thanks, guys.

I knew about the radio condenser on the generator. But I always thought that the condenser on the coil, shown in pics that Stovebolters posted, was a points condenser that had been moved from under the distributor cap to the coil. (Couldn't see how that would work, but that's what I thought.)

You don't know if you don't ask!

Jim Carter gets these suppessors from me , that price is a good deal list is $21 we may run out of them?

Any .5 mfd cap.will work,they are usually stamped on the end of the can.

Lonnie; Model A Fords had the cap. mounted right over the ex manifold and they burned up quite often. I spliced a lead on one and mounted it on the firewall and it ran for years.

Yep, just checked out the three on the truck I got from JC a couple of years ago, .5µF
each of them.

For the uninitiated who think an ignition condenser is the same as a noise suppressor
because they both look the same, they’re not. But the ignition caps are .22µF which just
might be enough capacity and I don’t know how you could tell what the dielectric
strength is or what the voltage spikes would look like at the coil plus side, regulator bat.
terminal, the generator armature and at the hot side of the ammeter.

Will a .22µF cap work as a noise suppression component? I don'o, maybe? Perhaps Bill
can elaborate on the technical aspect of it by pointing to or drawing it out schematically,
or explaining what determines the values?


DG

Boy you really dont beleive anythig I say do you?

Not that at all like that Tom, you are absolutely correct. If I doubted you I might have
pressed you for your source. I just happen to be one of those people that doesn’t run on
faith alone, I need to see the whole picture rather than just get a glimpse of what’s going
on, and I just happen to have a few meters that can check capacitance. Some folks are just
as happy as a pig in the mud to get into their car, turn the key and drive off not caring
exactly what just happened to get them moving. I want to lift the hood an understand the
sequence.

My wife and I took flying lessons back in the 70’s and after we got our license she was
content to rent planes and fly her friends around the pea patch. I on the other hand had to
know more about the machine so I studied the ins and outs of aircraft construction and
scratch built a biplane and then a high wing two place cabin plane. So you see, I just want
to understand how it works, not doubting your expertise at all.

I'm a rank amateur at radio restoration, I've only done a couple of total restorations over
each winter since I got interested in the radio hobby a couple of decades ago. I've studied
enough radio theory to understand the roll that capacitors play in controlling a radio
circuit but the noise suppression application has me a little cornfused.

Ignition system noise or noise itself covers a whole rash of frequencies and I’m trying to
understand how you would figure the correct capacitance or voltage rating for the
different applications in the engine compartment.

The original radio installation in the AD trucks used several different values for noise
suppression and I’m interested in why or how we can get away with a one-size-fits-all
approach today:
For instance, the regulator used a pn.1912900 condenser, the generator used a
pn.1911095 condenser, the coil used a pn.1910147 condenser, the coil high tension lead
used a pn.1887829 and a pn.7557919 was used at the ammeter.
Seeing the how much penny pinching went on at GM back in the day it seems odd that
the bean counters would give the go ahead to the engineers to specify all those different
values if one value would have served the purpose. And they specified those different
values over the entire run of the AD series.
Denny Graham
Sandwich, IL

Thanks, Denny.

I installed all the original parts from a NOS Radio Suppression Equipment kit on my Suburban. The link I gave above showed that there were different part numbers for the different condensers.

I wondered why the condensers were different - I appreciate your earlier clarification and later explanation.

Maybe I put the different condensers in the wrong locations - maybe they are marked with the PN or the rating - maybe I'll remember to look when Spring comes?

See what'cha got started Lonnie!!! Well Tim, next to Brad Allen you are probably one of
the very few that has the original NOS parts in hand.

Let me say again, Bill is our expert here so if I'm off base with any of this he’s welcome to
correct me. Capacitors are notorious for not having an indefinite shelf life and are the
number one cause of problems in electronics. Electrolytic caps which are used as filter
caps inside the radio are especially bad because they use a semi-liquid or more often a
paste as the dielectric and they tend to dry out.

The capacitors used originally for noise suppression filters are dry paper capacitors. The
older ones used a paper dielectric where most now days are made with Mylar or some
other poly dielectric. But because they are dry doesn’t mean that they will last forever,
they are subject to moisture absorption and damp paper doesn‘t make a very good
dielectric. This results in a shorted capacitor, also the thin aluminum plates corrode
forming aluminum oxide which is non conductive. A paper capacitor doesn’t have to be
in service to go bad they often go bad just sitting on the shelf. I once bought a VERY
large cache of NOS Sangamo, Solar and Micamold molded paper caps. I thought I really
scored but when I got to checking them, not a one of them were good they had been
stored in an old open barn since the 50’s. when you broke them open the plates were just
white powder. Not all old paper caps go bad over time. I’ve seen ones that were kept in
dry conditions that still tested good after 50-60 years with no leakage and right on spec.
The later Mylar caps seem to fair somewhat better, but aluminized Mylar is still
hydroscopic and can hold moisture.

If you get a chance next spring Tim, I’d really be interested in seeing what the capacitance
of those original caps is that were in the kit. Any one of your physics prof’s would have a
simple hand held multimeter with a capacitance function on it, maybe you could borrow
one for an evening. It only took me about 10 minutes to pull the lead and measure the
ones on my ‘50 with a $25 Harbor Freight meter. I do have an HP 4262A LCR bench
meter that I use if I need a really accurate measurement.

Denny Graham
Sandwich, IL

Now I got your heart beating.An interesting story on radio noise.The dealership sold a new car probably in the late 50s.The owner brought it back with an occasional POP in the radio.We checked all the usual stuff and found nothing.Being about 30 miles from the delco radio plant in Kokomo In. we took it over there. They concluded static electricity was build ing up on the curb feelers the owner had installed.Took them off and the pop was gone.By the way I bought several CB radios from this plant that they decided not to market.Probably made by some one else but had a big GM on the face.

GM CB radio??!!! That sounds cool.

After reading all this, and what's in the radio install/service notes, I'm always amazed that I never had trouble with noise on the radio I had in the last truck I had. I suppose noise is less of a problem these days with the new-fangled spark plug wires we use. Perhaps when I put the radio in my panel truck, it will make up for it, by having tons of noise!

Its wierd sometime you could put a radio in something and have no noise and others would drive you crazy.Of course FM did away with a lot of noise.