'THAT' Capacitor. What is it?

CAWOS ? I had a guess, what does it stand for?

[AC/HL]

'Change all waxies on sight' according to post 11.

[Paul_RK]

CAMOS, surely: Mouldseals are grim but I haven't found Hunts electrolytics to be worse than anyone else's. But, yes, such acronyms seem best avoided, and this particular family of them refers to a practice I'm never likely to be tempted to engage in.

Paul

[turretslug]

Though "waxie" could itself need a bit of further explanation for the uninitiated- many mica plate types have a good dolloping of wax on them but are amongst the more trustworthy vintage types. There are always the excusable exceptions after 50-80 years though.... As they are often front end/oscillator/IFT types, sometimes with "odd" values, blanket changing could unlock a host of un-necessary troubles.

[Paul_RK]

And conversely there are the American "Micamold" components, some at least of which, the name and moulded lozenge-shaped housing notwithstanding, are actually waxies in disguise, and not very good ones at that.

[DKW F102]

Hi again. Thanks to everyone who has explained about the 'audio coupling capacitor'. As I said in my second posting, I have been replacing the 'audio coupling capacitor' as a matter of course ( not realy knowing what it does) while changing all of the other wax paper capasitors, or to use a new confusing term ' Toffees' (so called as they are toffee colour and sticky too). I geuss that all of the resistors and capasitors should ALWAYS be checked during the restoration of a radio / amplifier. If they are not in spec then it pays to change them. I do wonder if people who talk about 'the valve sound' are used to sets with duff resistors and capasitors making them think that all valve stuff should sound like that. Anyway, I'm of to measure some 'audio coupling capacitors' ... !!

[G8HQP Dave]

Just to confuse things, there are sets where the coupling capacitor to the output valve grid does not come from a preceding anode so a little leakage does little harm. We don't want folk searching high and low in the circuit diagram for a cap which is not there! (Example: Pye P45).

[AC/HL]

Within the Forum we soon get an understanding of the shop talk slang. I struggled with "that capacitor" initially, with exactly the same question. I can't remember how it dawned on me, quite possibly a previous post just like this one. As Dave says in post two, the ever present search box will provide chapter and verse on this and most other subjects.
Personally, I always think in terms of paper rather than either waxie or Hunts, both of which are ambiguous, for different reasons.
We also sometimes get the statement that "there is no that capacitor" in a radio. The best course of action may be that when replying to a new member, or one that has been honest and made it quite clear that they have no experience, we refrain from using that or any other slang. It still leaves the problem of people reading posts from experienced members, but there is little that can be done about that as with everything.

[Herald1360]

Guess what? If you google "that" capacitor the top few returns point you to explanations on this forum......

[kalee20]

Originally Posted by Herald1360

Guess what? If you google "that" capacitor the top few returns point you to explanations on this forum......

Great Scott! He's right! And I didn't even use quotation marks!

[Radio Wrangler]

... Found even though "That capacitor" is the shortened form, lacking the essential central adjective which is routinely included after the "That capacitor" has been found to have taken out the output and mains transformers.

David

[AC/HL]

That's because the Google spider is busy indexing the Forum as we speak. This thread will appear in the list in due course, I've seen it happen within hours.
A quick check shows it reading a thread called "Winter Project" among others. The images spider is viewing "Re-stuff TCC capacitor from a Quad II". MSN is reading "Bush TV22 totally stuck see pics" and there are several others at work too.
Posts from this Forum are usually at or near the top of most related searches.

[dave walsh]

I suppose the real question is why more people don't think to use google or the
specific "search this forum" feature that was specially created by Paul Stenning on here to help? Yes it's nice to ask a friendly Forum but only if you're really stuck [in my view]. Most questions have been asked many times already so the answers are already there. When they are not-it's a different matter
Dave

[stevehertz]

Originally Posted by DKW F102

I geuss that all of the resistors and capasitors should ALWAYS be checked during the restoration of a radio / amplifier. If they are not in spec then it pays to change them.

When you say "in spec", don't just check capacitors for capacitance value, check them for resistance values too. Mainly, that's how wax caps (and other types) are 'bad', they have capacitance and resistance, there should be infinite resistance (approaching if not at, open circuit).

Originally Posted by DKW F102

I do wonder if people who talk about 'the valve sound' are used to sets with duff resistors and capasitors making them think that all valve stuff should sound like that.

I firmly believe that that is the case - certainly with guitar amplifiers where players (myself included sometimes) are looking for a particularly gnarly, nasty distortion, and the out of spec and faulty components provide that. I remember the late great Rory Gallagher complaining that he had had his vintage Fender amplifier overhauled and it came back with the sound ruined. Doubtless the tech found some leaky caps and resistors out of spec, changed them and the amp was much cleaner afterwards!

[DKW F102]

Hi. Stevehertz ... When you say to check capacitors for resistance, how can I tell what the reststance should be ? I've only seen uF/nF/pF and the voltage on them. Is this the E.S.R I suppose ? I bought an E.S.R meter when I started geting my kit together but could not realy understand what it was supposed to be for, so have not used it since. I measure my resistors with my AVO 8 and my capacitors with a Greyshaw CR 50 C/R Bridge. Both the AVO and the bridge have been overhalled /aligned by a kind member of this forum. Am I missing something I should realy be paying attention to ?

[julie_m]

I think every subculture has its own slang. When I worked in the industry, diodes did not have cathodes -- they had business ends. And "That capacitor", said in the right tone of voice, carries a delicious suggestion of infamy which will not be lost on anyone who has seen the devastation it can wreak if leaky.

Even if you were trying to use strict scientific terms, it could still equally be described as an audio coupling capacitor or a DC blocking capacitor!

It's common courtesy to define a term when first using it around someone who may not be familiar with it says she, who is recently guilty of forgetting that not everybody has studied physics to quite the same level. But it's not as though this forum is a secret society whose members know one another by their special words. If it was, there would hardly be an open, sticky thread on the subject, would there?

[crackle]

If you are checking a capacitor for DC resistance, which as mentioned earlier should in theory be near infinity, you should measure with a voltage source close to the working voltage of the capacitor. If the capacitor allows any DC current (fractions of mA's) to pass at this voltage then it is said to be "leaky" i.e. leaking current. (not necessarily leaking its contents)
The degree of leakage allowable depends on the application of the capacitor, but in the case of the audio coupling capacitor, if it shows any leakage then replace.
ESR meters like the PEAK ESR60 are really only useful for higher value capacitors like electrolytics, ideally the ESR should be zero.

Mike

[Radio Wrangler]

You can still have poor leakage on a capacitor with good ESR, and vice versa. The two things are quite different.

David

[stevehertz]

Originally Posted by DKW F102

Hi again. Thanks to everyone who has explained about the 'audio coupling capacitor'. As I said in my second posting, I have been replacing the 'audio coupling capacitor' as a matter of course ( not realy knowing what it does) while changing all of the other wax paper capasitors, or to use a new confusing term ' Toffees' (so called as they are toffee colour and sticky too). I geuss that all of the resistors and capasitors should ALWAYS be checked during the restoration of a radio / amplifier. If they are not in spec then it pays to change them. I do wonder if people who talk about 'the valve sound' are used to sets with duff resistors and capasitors making them think that all valve stuff should sound like that. Anyway, I'm of to measure some 'audio coupling capacitors' ... !!

Originally Posted by DKW F102

Hi. Stevehertz ... When you say to check capacitors for resistance, how can I tell what the reststance should be ? I've only seen uF/nF/pF and the voltage on them. Is this the E.S.R I suppose ? I bought an E.S.R meter when I started geting my kit together but could not realy understand what it was supposed to be for, so have not used it since. I measure my resistors with my AVO 8 and my capacitors with a Greyshaw CR 50 C/R Bridge. Both the AVO and the bridge have been overhalled /aligned by a kind member of this forum. Am I missing something I should realy be paying attention to ?

The simple way is to connect your capacitor to your meter which should be set to read 'resistance', and set to 'high value' ohms range, the highest range it has. If you get any resistance reading - a low value is a definite no-no - but even a high value (100's of K ohms) means that the cap will be able to pass DC and should be replaced. Ideally you want to see a reading that is very high; in excess of 10 or 20 millions ohms (Megohms), or better still, 'open circuit' ie an infinitesimal amount of resistance.

[G8HQP Dave]

Originally Posted by DKW F102

Is this the E.S.R I suppose ?

No. ESR is Equivalent Series Resistance, which is relevant for electrolytic capacitors and irrelevant (being virtually zero) for almost all other capacitors. ESR is irrelevant for a coupling capacitor even when an electrolytic is being used, unless the ESR is astonishingly high.

For coupling capacitors the resistance we are interested in is parallel to the capacitance, so in a sense the opposite of ESR. However, it is conceivable that some cheap capacitor testers could confuse leakage resistance with ESR, as they have the same effect on AC phase shift but for different reasons.

I bought an E.S.R meter when I started geting my kit together but could not realy understand what it was supposed to be for, so have not used it since.

An ESR meter is for measuring ESR.