What value is this capacitor?

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My dad gave me this data sheet for diagnosing an ignition problem on a GM truck (he's a mechanic). He was wondering if I had a cap that would work which I do, but...what value do you think this cap is? The datasheet clearly shows a capitol M which is Mega by convention. I know that can't be possible, so I am learning towards 0.33 millifarads which is 330 microfarads. Could it also be 0.33 microfarads though? I wouldn't put it past them.

Chief Tinkerer

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HAHA but what is the voltage rating of the beast? That's just as important.

If it's the old fashioned cap across the points (and to the coil) you may be able to get something from a wrecker.

I would go with the 0.33 microfarads guess as everything else is capital not just the M.

John Samperi

Ampertronics Pty. Ltd.

www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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.33 microfarad, and for messing with ignition coils it should be rated at least 400 volts

Tom Pappano
Tulsa, Oklahoma

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triden wrote:
My dad gave me this data sheet for diagnosing an ignition problem on a GM truck (he's a mechanic). He was wondering if I had a cap that would work which I do, but...what value do you think this cap is? The datasheet clearly shows a capitol M which is Mega by convention. I know that can't be possible, so I am learning towards 0.33 millifarads which is 330 microfarads. Could it also be 0.33 microfarads though? I wouldn't put it past them.

Here are my two cents, after google[PIC]]

1)http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c15280070696

2)http://www.ebay.com/itm/CDE-WMF05P33-33-MFD-50VDC-Capacitor-/380514289063?pt=LH_DefaultDomain_0&hash=item58986b45a7

[img]http://i.ebayimg.com/t/CDE-WMF05...$(KGrHqV,!n0FBZy3hOwvBQoV5p76hg~~60_57.JPG[/img]

From Idea To Invention

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Or use a 'condensor' that is usually on the side of the distributor. Being a mechanic, I dare say he would have one of these handy.

Looks like a simple method of checking the ignition coil.

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Doesn't the SI prefix "M" mean mega? I vote for 0.33 mega farad.

- S

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mnehpets wrote:
Doesn't the SI prefix "M" mean mega? I vote for 0.33 mega farad.

- S

It does now, but... in the days of my childhood it was micro. Obviously some corners of the technological world have been lagging behind :lol: And that cap above is only rated for 50VW ... need 400VW at least.

Ross McKenzie ValuSoft Melbourne Australia

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I agree with Ross. In the 1930s and 1940s, electronics was not very international. In the UK, we still used feet, inches, lbs, BTU, ...

I doubt that anyone had ever thought of using 'u' for greek mu or 'micro'. I also doubt that anyone had ever made a milliFarad capacitor 70 years ago. Nowadays 1000uF (1mF) electrolytics are common. I doubt if a MegaFarad capacitor will ever be manufactured.

David.

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I should have also added that picofarads were shown as MMF (micro micro farads).

Ross McKenzie ValuSoft Melbourne Australia

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Boy do I feel old today...

Here is a photo of a couple of "MFD" caps from my parts bins. I add two "color dot" caps also, and no, I don't recall how to read them. Guess I am getting Alzheimer's as well as old age...

The 600 V and 1000 V caps were common back then. Such parts were often used in tube radios, TVs, 1 KW transmitters, etc.

As stated above, the "MFD" is what we would now call microfarads.

JC

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We used to say things like "100 mickey-mike" for 100 MMF, etc. If you go back far enough you can find schematics where a resistor designated "100M" meant 100 kohms, not 100 meg.

Tom Pappano
Tulsa, Oklahoma

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In the late '70s I had a college instructor who was "educating" us about what we'd find in the real world. He told us that capacitors would be marked MF and MMF. Except that I already knew that uF and pF were replacing MF and MMF and had been for several years at that point. I got this from reading hobbyist magazines. The university did get around to trying to sack him, never did hear if they succeeded.

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So I am getting all sort of old-timey here but I suspect the problem at hand is ignition misfiring. I also suspect the vehicle has points rather than electronic ignition. There used to be a thing called a condenser mounted to the side of the distributor. I think that is is the part that is in question. Do a Google search on "ignition condensor" and you will find all the results you need. I may be wrong as I usually am so let me slide on this one. I just ask when was the last time anyone has ever adjusted the points on their car?

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Plenty of old tractors around, my Ford 800 was produced the year I was born. No diagnostic port, when it fails you have to rely on your gas-air-spark-timing knowledge. With that, a wrench, screwdriver, tirepump and baling twine will almost always get you back to the barn.

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Based on size (it's approximately a scale drawing), application, apparent era of drawing, and the lack of polarity marks, what you need is almost certainly a 0.33 microfarad capacitor. That was a standard size, way back when (0.33milliFarad = 330 microfarad, and 0.33 megaFarad, not so much...)

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I am also pretty positive MFD means microfarads. Thus 0.33 MFD means 0.33 microfarads, but I would prefer to say 330nF or nanofarads for some reason.

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Back in the day, MFD = uFarad, MMFD = uuFarad = pF. The change in the US came around 1958-1960.

Jim

 

Until Black Lives Matter, we do not have "All Lives Matter"!

 

 

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While MF (megafarad) is still off in the future, kF (kilofarad) is quite common in the supercapacitor world.
As for M versus m, that's a pet peeve of mine. The last 1MW laser pointer I bought seemed a bit week for a megawatt...

I still remember the cartoon in Radio Electronics of the truck showing up with a water-heater sized capacitor on the back, and the delivery guy asking "Who ordered the one farad capacitor". Once I started seeing the 1F supercaps, the joke lost its punchline.
/mike

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Hi, if its about car ignition it definitely is 0.33 micro farad or 330 nano farad but should also be able to handle high voltage peaks, 400 to 600 volt, caused by ignition coil. And also keep in mind that tempetrature near the engine is pretty high.

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I found that a condenser for old Ford ignitions (NAPA Echlin Part# FA49) meets the .33 MF specs. Now I have to try it and make sure I hook it up correctly.

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I'd think any auto parts store would have ye ole distributor capacitor. they were always inside. Metal sleeved. Screw mount bracket and 2 inch long black wire with terminal lug.

We always changed points & condenser and usually, spark plugs, in a "tune up" every 20K miles or so.
Before electronic ignition and fuel injection.