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Old 4th Dec 2015, 12:26 pm   #1
Ian - G4JQT
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Default Modern HT smoothing caps

I have some new F&T AL-ELKO type LFAZ 16+16uF 500V smoothing caps.

The inner and outer foils are not marked, just two + marks and one - mark stamped into the connection studs.

I'm assuming that their construction means there is no difference and such markings (usually a yellow and red blob, or other indications on the can) are therefore irrelevant.

Can someone just confirm that this is the case?

Thanks.

Ian
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Old 4th Dec 2015, 1:19 pm   #2
David G4EBT
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Default Re: Modern HT smoothing caps

We invariably refer to twin section capacitors as 'smoothing capacitors' but to be strictly correct, the first section is the reservoir capacitor and the second is the smoothing capacitor.

When twin-section capacitors are of the same value – say 16 uF as in your case - the reservoir capacitor will usually be identified by wording on the can with the term ‘Res’, but if not, the tags will usually be marked red, yellow and black, and the can may well state ‘Red Outer’, but if there is no wording, red is the reservoir, and yellow is the smoothing capacitor (the one after the resistor between the two sections of the capacitor). The reason that it’s preferred to use the outer capacitor for the reservoir capacitor is that it works the hardest, and being the outer one, is more effectively cooled.

In your instance Ian, given that neither are marked to identify the outer, presumably, as you say, it's immaterial.

On capacitors where there are two different values, eg, 32+16 uF (as in the DAC90A), the 32 uF is the reservoir capacitor, and the 16 uF is the smoothing capacitor. If not stated on the can, the 32 uF will be the red tag, and will be the outer. On most capacitors there will be a black tag on which to wire the negative connection, but if not, it will usually say: ‘Can is not Isolated’ and the can is therefore the negative connection via the chassis clip. (Sometimes there will also be a solder tag at the top of the can, as on the DAC90A, but that tag is rarely used).

Hope that's of interest.
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Old 4th Dec 2015, 1:36 pm   #3
Ian - G4JQT
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Default Re: Modern HT smoothing caps

Hi David and thanks for the info.

Yes, I knew about the red being the outer reservoir, yellow smoothing. I've also seen symbols (a triangle and a square I think) stamped onto what would be the red or yellow terminals with the key printed on the can.

I guess you're right when you say if they're the same value it doesn't mater.

Regards,

Ian
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Old 4th Dec 2015, 1:41 pm   #4
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Default Re: Modern HT smoothing caps

In my experience, the square and the triangle markings are most often found on capacitors of USA origin.

Al.
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Old 4th Dec 2015, 3:39 pm   #5
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Default Re: Modern HT smoothing caps

I wonder if the outer case contains two separate capacitors either side-by-side or vertically stacked, thus making which one gets used as reservoir immaterial- the SMPSU world has given us such compact HV electrolytic capacitors with excellent performance that this might be a tempting approach nowadays. Sort of "re-stuffing at manufacture".

Mind you "red outer" or similar phraseology was such a familiar marking on traditional multi-section types that it might have added a touch more authenticity!

I always considered dual- etc. section types as a manufacturing economy measure- by the simple expedient of slitting one of the foils and adding a terminal or two, a capacitor of a given value could be made into two or more aggregating to the original value in one can with one clamp. Anyone else remember those early '70's Philps low-voltage cans of 2350 + 2350uF, 3400 + 3400uF etc., obviously just made from standard 4700, 6800 and so on?

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Old 5th Dec 2015, 11:13 pm   #6
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Default Re: Modern HT smoothing caps

I use lots of F&T caps and have never bothered with which is which. I use them mostly for guitar amps and as yet!! havent had any failures: and they do work hard.
Joe
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Old 6th Dec 2015, 3:12 am   #7
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Default Re: Modern HT smoothing caps

Quote:
Originally Posted by Skywave View Post
In my experience, the square and the triangle markings are most often found on capacitors of USA origin
Philips used those markings as well.
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Old 11th Dec 2015, 3:14 pm   #8
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Default Re: Modern HT smoothing caps

Is/was there any standardisation of what the square and triangle marks meant?

Al
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Old 11th Dec 2015, 4:57 pm   #9
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Default Re: Modern HT smoothing caps

A 1970s capacitor (Philips?) uses the square to denote positive and triangle for negative.

An unidentified cap uses a square, triangle and circle to identify the three sections.

A Grundig 3 section capacitor uses a triangle for the 100uF and a square for 'Auss C'.
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Old 12th Dec 2015, 11:24 pm   #10
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Default Re: Modern HT smoothing caps

My German is pretty well non-existent. I do know that aus means out. Does 'auss C' mean outer(reservoir) capacitor?

Al
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Old 12th Dec 2015, 11:48 pm   #11
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Default Re: Modern HT smoothing caps

Is the 'auss' in 'auss C' spelt with one 's' or two. My knowledge of German is slight, but AFAIK that should mean outer Capacitor. I've often used F & T Electrolytic Capacitors, and not had any problems with them, and I could't say with any certainty that I've always wired the outer one as the reservoir. My usual procedure is to orient the new cap. the same way as the original, then connect the wires to the same tags as they were on the old one. Since the 3 tags on a F &T Cap. are arranged in the same triangle pattern as those on most old dual cans, this, AFAIK, should ensure that the outer cap. in the new can is wired directly to the rectifier.
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Old 13th Dec 2015, 11:05 am   #12
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Default Re: Modern HT smoothing caps

"auss C" is Ausstrom C or "outflow C", i.e. supply rail C (think "stream", bringing us to current!). There's a good chance that "Auss A" would have been for the output valve(s) anode supply, "Auss B" through hum-cancelling output transformer primary, smoothing resistor or choke (in order of likeliness) for output screen grid(s) and most of the rest of the set and "Auss C" for low-level audio and other hum-critical sections- things could get a bit formulaic, but then there had been a couple of decades of refinement.

"Triangle" and "square" turn up in a lot of places, sometimes as symbols for "three" and "four", sometimes simply because they're easily recognised throughout cultures as distinguishing marks.

"A", "B" and "C" supplies above not to be confused with US terminology- no wonder agreeing international standards and conventions can get drawn out.
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Old 13th Dec 2015, 11:45 am   #13
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Default Re: Modern HT smoothing caps

If I read turretslug's post correctly, then 'auss C' is indeed the reservoir capacitor connection, since it is wired to the rectifier's output.
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Old 13th Dec 2015, 2:16 pm   #14
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Default Re: Modern HT smoothing caps

I haven't seen the circuit in question, but designation could be subject to designer whim- come to think of it,the lettering sequence could be the reverse of how I'd suggested with "C" being the highest voltage, least filtered rail, in which case it would be the outermost and reservoir section, though this would be against sequential convention.
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Old 13th Dec 2015, 4:21 pm   #15
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Default Re: Modern HT smoothing caps

I found this schematic on the NVHR website.

http://5.132.37.30/nvhr/Grundig_2420U.pdf

It shows the A section of the smoothing block as the reservoir.Subsequent letters are for capacitor sections further down the smoothing chain.

Al
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Old 14th Dec 2015, 4:38 pm   #16
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Default Re: Modern HT smoothing caps

I purchased two new 125uf 500v caps a few years back that had screw terminals with no identification from a locally held radio jumble, to repair a PSU for a disabled radio ham friend. I was told by the vendor that the polarity didn't matter, but not to reverse the connections once they had been powered up. We took the man at his word, but stood behind the workshop door at switch on! They have been working faultlessly ever since. They had a blue plastic film over the can, had the word powerlytic printed over the value and rating, and were made by Sprague. Was this a known thing, or were we just very lucky?
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Old 14th Dec 2015, 10:03 pm   #17
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Default Re: Modern HT smoothing caps

An interesting "I wonder what happens if....." opportunity missed there.
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Old 15th Dec 2015, 3:20 pm   #18
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Default Re: Modern HT smoothing caps

From the above info I have put this spreadsheet together. Hopefully it will help with difficult to identify badly marked multi section.

Can anyone expand on or clarify the data in the spreadsheet.

Al
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Old 15th Dec 2015, 6:39 pm   #19
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Default Re: Modern HT smoothing caps

Quote:
Originally Posted by Pat Pending View Post
Was this a known thing, or were we just very lucky?
I think you were lucky, not the same value but the in the photo you can see the + sign and just see the vent.
Unless these are a different type to the ones you fitted.
Frank
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Old 15th Dec 2015, 7:08 pm   #20
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Default Re: Modern HT smoothing caps

Regarding the Grundig capacitor I described in post 9.
I assumed that Auss C was an abbreviation so I started looking through an online German-English dictionary.

I got the impression that it refers to an outlet. Ausschenken can be translated as 'to pour out'.

That gives me the impression that the 'Auss C' section is a smoothing capacitor.
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