Condensers again

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Excalibur
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Condensers again

#1

Post by Excalibur »

Anyone having trouble with condensers? Lotta talk around about how crappy they are these days.

My failed pile includes new branded ones, Bosch and Blue Streak. Currently I've fitted a 3rd new (Daiichi) condenser. It's Japanese NOS & "found" in the shed, the pattern is for Brit bike but fits the clamp-bracket. Been 3 weeks, so far so good.

In the 70's I must have fitted 100's of sets of points to vehicles of all types. It was rare to fit a condenser. They didn't seem to wear out.. Typically we'd only install a condenser if the look of the contacts dictated it or if we were chasing a problem and trying "everything".

I ground the crimp off 2 old condensers, opened them up to get an idea of what I was dealing with. One of these I'd previously marked as bad. They are very cheaply made. Just a few cents worth!! Inside is a tightly wound coil of silver foil separated by plastic film. I unravelled one coil looking for signs of arcing or short but it was OK. One condenser looks like it has been arcing where the wire lead connects.

My thought is vendors are getting condensers made in countries with cheap labor. A modern condenser isn't like condensers of old. I believe makers aren't putting the same effort into producing them.

I'd like to find some NOS condensers, back when they came in a nice little cardboard box and the condenser itself was brand stamped. Perhaps I find a retired AutoSparkie or hunt some out at swapmeets.

I looked up the HD part number 32726-30A (fits '41 - ** )Was that a Delco? Is the Delco part number known?

Refreshing my memory about microfarad ratings, condensers are in .18µf - .33µf range for points ignition. In theory the µf rating could be raised or lowered to correct the transfer of metal on the contacts. At the moment I'd be happy just to get a good condenser of any µf within the usable range.

Today I went to a local Vintage Car Club gathering and was able to get another NOS condenser, suspecting it's a Daiichi though a bit bigger in length it's the same diameter. Of note there were hundreds of nos condensers on the shelf but 90% had brackets spot welded on.

Ok, so that's my rant over. Hope to hear from anyone with any points of interest, details, comments, experiences, opinions etc.
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Frankenstein
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Re: Condensers again

#2

Post by Frankenstein »

I feel your pain, believe me! I wouldn't doubt that they all come from the same factory in china. Unfortunately, I'm afraid spending more just gets you a more expensive box :( I have heard some good reports about NAPA's stock, lots of farmers hereabouts that still need points for old machinery. Your new old stock idea is a good one, another item I keep an eye out for at the swap meets.
Believe it or not, I'm investigating an electronic ignition setup that's fairly cheap, and will fit entirely inside the breaker ass'y. And, made in USA. Talks are in early stages and the hope is that no modification to the stock mechanism is needed. I know points replacement electronic devices are out there, but this does the whole thing, electric advance retard and also vacuum retard on hard acceleration. Having lived electronics for a living I'm not put off by the thought of depending on solid state devices, but stayed with points for cost and the simple reason of not being able to fix it with a matchbook along the side of the road.
DD
Excalibur
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Re: Condensers again

#3

Post by Excalibur »

Thanks for the thoughts.

Elsewhere I found a blog of a guy who tested failed condensers before dissecting them. Interestingly they pass various electrical tests but upon opening them up, arcing was noted.
http://www.nonlintec.com/sprite/cap_failure/

I too am looking at electronic breakers. I made several prototypes but the back emf appears to be what's toasting the hall sensor. More recently I decided on another approach. This uses existing components from '80's/90's cars before the added complexity of electronic advance. I've found all but the wiring plug to begin assembly. The object is to carry a spare ignitor plus run a coil which gives very high energy spark. Also have the ability to swap back to points on the spot. Additionally, I wondered if one of those Pertronix Lobe Sensor ignitors would work on our odd-fire cam lobes?

I might have spoken too soon about the Daiichi condenser. Engine got progressively difficult to start. Then I cleaned the points and fitted the 2nd NOS condenser. The bike then started instantly and very convincingly.

I began thinking that some of my assumptions might be wrong. I wondered why the engine responded so well to a clean of its' points? Could this many condensers really be all bad or was there something else wrong?
I conducted a few tests and checks:
Battery voltage 12.6v
Battery: Motobatt 8ah
Running volts 13.8v
Coil draw 2.3a
Coil ohms about 5

What am I missing?
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Re: Condensers again

#4

Post by Frankenstein »

Not missing much.
Funny, went to a swap meet today nearby, and found a whole box of daiichi condensers and points for perhaps Hondas? All new old stock.
A gentleman did a study of condenser failure in magnetos a couple of years ago and published the results in the AMCA magazine. Well schooled in electronics, he also had the test equipment to bench test condensers and determine failure modes.
If I recall the jist of his findings, it was the high instantaneous energy present that was the destructive factor, not just current and voltage ratings. The sharp bursts of actual power, current times voltage, that did in the items under test.
He determined an appropriate replacement industrial capacitor, only to have the manufacturer discontinue it 6 months later.
A magneto condenser is a more challenging application than a Kettering ignition system, in that the higher the rpm's, the higher the voltage/current present that must be withstood.
The bottom line is current product sold for ignitions are just plain cheap, foil and insulator not made to let us say, military spec's. Detroit is not buying them by the millions and demanding a minimum quality standard, so we're screwed. And unfortunately, they deteriorate with age, albeit it takes a long time, so new old stock is beginning to not be a viable option any more either.
On the electronic scene, the Bosch 373 is an ignition driver, meant to drive a coil and isolate the trigger from the coil's nasty side effects. Also do a search on ignition modules for ready made packages to perform the same function.

DD
kell
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Re: Condensers again

#5

Post by kell »

Hey guys.
Been gone from the board for a while. I have some ideas to throw out there for the folks with ignition woes.
I experimented with various homebrew electronic ignition circuits on my old pan.
The most complicated thing I ever built was a hall effect circuit with little magnets on a spinning plate above the hall sensors, which I mounted in the old breaker.
I'll not be discussing anything so complicated today. Instead I'll tell you how to build a circuit that takes the load off of the points so you don't need a condenser at all. The points do the switching, and a transistor in series with them does the heavy lifting by handling the voltage spikes.
Be forewarned, this circuit might not work so good on a 6 volt system; dunno, I never had one. But on a 12 volt bike it works.
It uses an Automotive Ignition IGBT (Insulated Gate Bipolar Transistor) in cascode with the points.
https://en.wikipedia.org/wiki/Cascode
If you look at the simple circuit diagram on the wiki page, the points go where the bottom transistor is, and the igbt goes above the points. The coil goes where the resistor is in the picture.
The gate of the igbt is connected to 12 volts so that it's always biased on.
The only igbt's I see on the market now are "logic", which means they take nominal 5 volts on the gate and aren't gate-rated for 12 volts. So you will need a couple of extra parts, a resistor in series with the gate and a 5 volt zener from the gate to the emitter. Or whatever voltage is appropriate for the igbt, it may be rated to handle something more than 5 volts. That's all, just three parts.
This link takes you to examples of a few igbt's
https://www.digikey.com/products/en/dis ... ageSize=25
I built and used this circuit. When compared with other possible circuits that use transistors to take the load of the coil and retain the points to trigger the switching, cascode works better than the other circuit configurations.
One nice thing about this circuit is that if the igbt fails, you can just remove it and go back to a straight points circuit, if you keep a spare condenser in your kit. It's unlikely that an automotive ignition igbt will fail, though. They are built specifically for driving ignition coils, they are produced by the millions, and I haven't heard of them failing. IGBT's are tough as nails.
On the subject of capacitors, you could just try an ordinary film cap with a really high voltage rating. I mean, if all the "condensers" being made now are crap, to hell with 'em.
https://www.digikey.com/products/en/cap ... ageSize=25
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Re: Condensers again

#6

Post by Excalibur »

Thanks for posting.

Studying my failed Daiichi, I note there are no stamp markings. It occurred to me that it could easily be some leftover condenser thrown into a Daiichi box. It came to me amongst quantities of surplus Brit bike parts. Either way I look at it, it's out on its' ear.

I'm with you on current ignition condensers are made too cheap. Talk is of condensers working OK to start with, then falling over or dead right out of the box.

Ok, yes, I have some BIP373 and a few GB14C40L. Easily they can switch a much more powerful coil. Looks like I need to de-couple the hall sensor as I let the magic smoke out of 3 halls in testing.

Kell, the cascode circuit is very simple and that is often best. I've been studying it and I think I understand how it works. I made a circuit diagram. Does this look right? The GB14C40L uses a voltage clamp on gate-emitter so I believe I can use 12v? I suppose it also means using a heatsink?
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Cascode IGBT circuit
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Re: Condensers again

#7

Post by rocket ron »

I've seen the following on one of the forums but haven't tried either yet. Has anybody tried them? Seem to be foolproof.

http://brightsparkmagnetos.com/easycap/ ... /index.htm

http://thorcap.com/index.htm

Ron
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Re: Condensers again

#8

Post by Buddhahoodvatoloco »

Wow, very, very interesting.
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Re: Condensers again

#9

Post by devon john »

i put up the thread on in England ,,Bright spark condensers and have been using them for over a year ,,

very small easy to cut to any shape and it works ,was told of them by a friend that fits them to magnetos ,, he's been doing it for a couple of years with no failures

john
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Re: Condensers again

#10

Post by fredotwowheels »

Something I have been wondering lately: Is there any reason why someone couldn't just run a modern capacitor? What is the faraday and voltage rating on a standard condenser?

EDIT: I now see that Brite Spark is exactly that, would be interesting to know the capacitor value.

EDIT AGAIN: Found the value. 0.15uF/0.22uF 630v.
Here you go, you can get one of these for $3
https://www.mouser.com/ProductDetail/AV ... 3sU1Q9E%3d
Maybe I will give it a shot, just solder one some resistor legs to either side and cover the whole thing with a heat shrink tube. You could get 10 for around $20 if this is the case. Maybe if I have good results I will make a tutorial video.
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Re: Condensers again

#11

Post by rocket ron »

devon john wrote: Tue Apr 10, 2018 7:18 pm i put up the thread on in England ,,Bright spark condensers and have been using them for over a year ,,

Couldn't remember where I'd seen it,just copied and saved the link. If you reckon they're ok I might give them a try.
Thanks
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Re: Condensers again

#12

Post by 108 »

I have a "48 Pan but I frequently work on old cars and I've had more bad condensers in the last 2 years than in the 40 years before! I've also been buying NOS Delco Remy condensers at swap meets, and you can often get nearly new name brand condensers out of junk yard cars. The transistor circuit is very interesting and I may try it out soon.
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Re: Condensers again

#13

Post by nan00k »

mmm, may bite the bullet and go straight to a magcap if all newer condensers are suspect, rather than carry a spare only to be let down.

have used a magcap on BSA magdyno rebuild, 100% success and very good tech' support.
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Re: Condensers again

#14

Post by Excalibur »

This is turning out to be a really interesting thread. Lots of contributions with a variety of tips and opinion. Please keep the comments flowing.

I've been studying the issue in spare time. Some very interesting information turned up. The author of the article set out to find the ideal capacitor. In the pic below he used a MKP1845. 0.22µf at 1000v.
Quote:

The Quest for the wholesome capacitor.
Lucas quote the capacitor value to be between 0.18uF and 0.24uf, so the preferred value of 0.22uF fits in well. The choice of a low loss dielectric capable of handling peak voltages of over 600 volts, high currents and high temperatures was narrowed down to polypropylene, a dielectric that’s been reliably used in high-current pulse-discharge circuits due to its low Rs and robust dielectric.. Two versions of the capacitor are suitable; the first can be housed in a thin copper tube soldered to the dizzy plate and retained in the distributor, the second is housed in some 22mm copper plumber’s fittings and fixed next to the coil with a flying lead going to the CB terminal. This is an improved position as the coil and capacitor form a tuned circuit

The article: http://ttypes.org/ttt2/conventional-ignition-systems with most relevant to us parts near the bottom.
:
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kell
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Re: Condensers again

#15

Post by kell »

Excalibur wrote: Tue Apr 10, 2018 10:32 am
Kell, the cascode circuit is very simple and that is often best. I've been studying it and I think I understand how it works. I made a circuit diagram. Does this look right? The GB14C40L uses a voltage clamp on gate-emitter so I believe I can use 12v? I suppose it also means using a heatsink?
Yes, the circuit you drew is correct. You'll want a heatsink.
And if you look carefully at the datasheet
https://www.infineon.com/dgdl/irgb14c40 ... 51cf0d240f
it specifies that you need an external 1k gate resistor. It's necessary to keep the voltage clamping diodes on the gate from burning up, especially since it's going to be exposed to continuous overvoltage. Take a look at the first circuit diagram at the top of the datasheet. There's no current-limiting resistor between the zeners and the gate pin, where you'll be connecting to the 12 volt source. So you really do have to put an Rg 1k resistor at the gate as listed under Vces on the first line of the "Absolute Maximum Ratings" table.

P.S, As a reminder, it's important that if you use this circuit, do not have a condenser wired across the points. My suggestion would be to leave the condenser installed, but disconnect the wire and tape it off. Then you have the option of converting back to straight mechanical points ignition on the roadside should the occasion arise.
You also have the option of connecting the condenser wire to the igbt collector, and the circuit would work. It will work in either case, whether you disconnect the condenser or connect it to the igbt's collector.
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