New Electrolytics - identifying the outer/reservoir section

[yestertech]

I have some of the F&T cap 'blue' replacements ( 8+8, 16+16 etc ) Is it possible to identify the outer section usually used for the reservoir cap ? I seem to recall reading somewhere that it was usually the left or right tag relative to the centre earth tag somehow. Does anyone know ?

Andy

[M0FYA Andy]

If it isn't explicitly marked, could that be interpreted as the manufacturer saying he doesn't consider it to be important?

['LIVEWIRE?']

IIRC, F&T Caps have no ID on either of the Positive Tags, so it may not be considered important which is the reservoir & which the smoothing capacitor section. If anyone know differently, please feel free to correct my assumption!

[GrimJosef]

Would a measurement of stray capacitance to the can tell you anything useful ?

Cheers,

GJ

[Boater Sam]

Does the 'scope method used with foil caps work? i.e. hold in hand, probe on terminal, see which gives largest 50c/s hum signal, is outer.

[Refugee]

Are they not in a metal can?
It will be more difficult due to the high capacitance shunting the 50hz anyway.

[Boater Sam]

Of course canned but I just wondered if you could tell. Never tried it, never needed to but the question was asked so I did my best to answer it, ignore if you don't agree, doesn't bother me.

[Refugee]

It is not impossible.
The outer would have a lower ESR to the can at high frequency.
It would not be easy.

[G6Tanuki]

Don't assume that there *is* an 'outer'! It's quite possible that rather than two long thin concentric windings the new capacitors use two short fat separate windings stacked one above the other. That would certainly be the easiest form of construction given the current trend for 'low-profile' PCB-mount electrolytics - just put two short-fat low-profile caps into one taller can.

If the manufacturer doesn't mark them it probably means it doesn't matter. I'd bet that the ESR (and so the amount of self-heating) of the modern capacitors is massively lower than any vintage capacitor you'll be replacing.

[David G4EBT]

We tend loosely to refer to 'smoothing capacitors', when the first one from the DC output of the rectifier is the reservoir cap, and the second one (after the choke or HT load resistor), is the smoothing cap.

Often, the reservoir and smoothing capacitor will be of the same value – say 16 uF. The reservoir capacitor will often 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 outer and hence, the reservoir cap, and yellow is the inner, and thus, the smoothing capacitor (the one after the H.T. load resistor resistor between the two sections of the capacitor). The reason that it’s preferred to use the outer capacitor for the reservoir is that it works the hardest, and being the outer one, is more effectively cooled.

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 to 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 be a solder tag at the top of the can, as on the DAC90A, but that tag is rarely used).

I guess that if there's no I.D. on the tags, the makers don't consider it an issue as to which is which.

The pic attached shows a typical two-section cap with the tags marked red, yellow, black.

Hope that helps.

['LIVEWIRE?']

F&T Capacitors have no identification as to which +ve tag is which, unless they have changed since I last bought one. I've certainly never seen one with red and yellow tags/terminals.

[AC/HL]

Perhaps modern ones are more efficient at dissipating any heat generated. Most components are more advanced than their predecessors.

[Silicon]

I measured the ESR of a few F&T double capacitors.

Most of them have a significant difference in the ESR. 1.2 and 1.7 Ohms for example.

I would be tempted to choose the lowest one for the reservoir capacitor in a high frequency power supply but in a 50 Hz mains power supply it may not matter.

[Diabolical Artificer]

I usually connect the rectifier to the left terminal, neg terminal down.

I checked a 16/16u I have on the scope and on an ESR, no difference detected between the two caps.
Here's the datasheet, it doesn't help us much.

Incidently though having the F&T logo it also says "Al-Elko Typ LFAZ" Are F&T and Al-Elko the same company?

Andy.

[Boater Sam]

Lots of silly babble and magic belief about German F&T caps on the web from the Audiophools.
Al-Elko is what it says on the tin, aluminium caps made in China. Did not see any connection though.

[Diabolical Artificer]

As far I'm concerned F&T are just decent caps that also have a generous max V, IE 500v instead of the usual 385/400/450v.

So your saying Sam that your average F&T cap is made in China not Germany?

A.

[Station X]

Al-Elko is an abbreviation for Aluminium-Elektrolytkondensator. (Me)

Where F&T caps are made I have no idea.

[turretslug]

I concur with the above two posts- workaday replacements, Al-Elko is just the generic diminutive/vernacular for Aluminium-Elektrolytkondensator and widely bandied about. I suspect that F + T caps probably contain two modern, Far East miniature electrolytics and a bit of padding to make an "olde-worlde" presentation, as mentioned. Whilst they may make quick, convenient replacements for existing multi-caps, I've always regarded the multi-cap concept as a flawed, thrifted compromise with its common negative hobbling the opportunity to thorougly keep ripple out of the system and would expect a new amp design to at least have a separate reservoir capacitor with direct and separated -ve return, if nothing else.

The folk with the silly babble and magic belief are probably the same ones that spend un-necessarily large amounts of money on cars for the sake of their badges- marketing people's favourite fodder. It's up to us to look beyond it.

Crossed with Station X!

[Boater Sam]

Originally Posted by Diabolical Artificer

As far I'm concerned F&T are just decent caps that also have a generous max V, IE 500v instead of the usual 385/400/450v.

So your saying Sam that your average F&T cap is made in China not Germany?

A.

Not at all, there seems to be 2 Al-Elko references, a German Station X found and the Chinese one I found.
If the F&T is of German manufacture as seem reasonable, the Al-Elko simply means its an Aluminium-Electrolytic.

Perhaps the Chinese company have registered the Al-Elko company name to gain some kudos off the back of F&T or just to confuse.

Its a murky world out there.

['LIVEWIRE?']

Having just checked www.askjanfirst.de On their site it states that F&T (Electrolytic) Capacitors are made in Germany. Obviously that statement doesn't guarantee or imply that the whole manufacturing process, from raw materials to finished product, is carried out there. However, I have often used F&T Can-type dual electrolytics and have had no trouble with them. As to using seperate reservoir capacitors, I take turretslug's point, but, as I'm sure he is well aware, just about all radios, record players, tape recorders, etc., originally used dual and triple 'cans'. Whenever possible I like to replace a faulty can with it's modern equivalent, usually, if not always, by using F&T Electrolytics.