Stumbled upon some coupling caps

operater

Member
2019-10-17 6:29 pm
Hi all! Look at those voodoo babies i stumbled upon just yesterday! Think those are from early 70s if I'm not mistaken. It is some sort of foil, MKP or MKT, but not sure... foil is a bit greasy to the touch - yep had to open one :eek:

Those things have some really mad drifts in values and quite some voodoo mojo to them. Very creamy and lush tone.

Whatta you ghuys think ?

[IMGDEAD]http://oprtr.win/shr/efco.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/efco2.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/efco3.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/efcos-l1600 (2).jpg[/IMGDEAD]

:eek:
 
I would guess 1950s, not 1970s. If they are waxed paper then they probably need to be binned. People will have spent years removing caps like this from old radios and replacing them with decent modern caps.

Change in value (typically upwards) means moisture has got in, which also means high leakage current. Don't use them as a coupling cap in a valve amp.
 

operater

Member
2019-10-17 6:29 pm
Most probably these are wax paper capacitors, especially if they actually have multiplied their nominal capacitance values.
Best regards!

Hi there Kay, thanks for input! This is exactly the case, many of them went up in value - they range from 138nF to 208nF but most are at 138-150nF. It's very interesting, I am curios now as to why paper waxes go up in value.

Best regards.

oprtr
 

operater

Member
2019-10-17 6:29 pm
I would guess 1950s, not 1970s. If they are waxed paper then they probably need to be binned. People will have spent years removing caps like this from old radios and replacing them with decent modern caps.

Change in value (typically upwards) means moisture has got in, which also means high leakage current. Don't use them as a coupling cap in a valve amp.

Hi again. thanks for all the input already.

Ouch even 50s? Really interesting. There was one that had the seal broken and it measured at 490nF :D ... most of the others measure from 138-150nF though. I'm even more curios, would it be that risky to use them if they appear sealed physically?
 

operater

Member
2019-10-17 6:29 pm

operater

Member
2019-10-17 6:29 pm
Okaaay. They definitely appear to be waxed paper! Here are some pics of the insides for the most curious :p:


[IMGDEAD]http://oprtr.win/shr/20191025_125537.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/20191025_125656.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/20191025_125718.jpg[/IMGDEAD]

[IMGDEAD]http://oprtr.win/shr/20191025_125814.jpg[/IMGDEAD]

Wow fingers very waxyy. Hope this stuff aint toxic LOL
 
I'd guess they may be ok to use for guitar tone pots, except that they are probably 10 or 100 times too large, both in capacitance and physical size. Ok if you like your guitar tone to be dark as the night sky.

I wouldnt choose to use them anywhere which may stress them - no way I'd use them for interstate coupling.
At most, input stage coupling....maybe.

I dont see the value in Mustards or Vitamin Q either, just another vintage con.

I think I'd have to be an idiot to pay €23 for one defective aged capacitor.

Any advert stating a component sounds one way or another, creamy, rich, smooth is an instant warning for me to avoid like asbestos.

After all, folks have been removing these degraded caps for years, in the process of refurbishing 30s valve radios.

I've probably thrown away 10s over the last 5 years.
 
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operater

Member
2019-10-17 6:29 pm
Really thank you for you comments, I love this talk and I'm really glad to be here.

However, I am of the opinion that saying that coupling caps sounding different are a vintage con is almost the same as if one would say that tube sound is a vintage con too.

But this is a story that has been told and re-told, it's a love or hate story and I would love that the both camps admit that they are exaggerating at least a little bit.
I wouldn't go too far but caps are often most used as filters in a circuit and affect a significant portion of the frequency spectrum so they inherently have to color the sound with their imperfections and introduce at least some harmonics be it in parallel or as a coupling. Whether those changes are perceptible is strongly subjective but doesn't mean it's a con or that they are in-existent.

It's always the doom and gloom talk when people mention vintage caps :D I really love this video on that topic: YouTube
 
Hi there Kay, thanks for input! This is exactly the case, many of them went up in value - they range from 138nF to 208nF but most are at 138-150nF. It's very interesting, I am curios now as to why paper waxes go up in value.


May I tell you? Within some decades wax paper capacitors tend to suck moisture from the ambient air. As (pure) water has a dielectric constant of 81.4, the previously dry paper also increases it's dielectric constant.
I've observed the same issue in the tonewheel generators of old (<1964) Hammond organs which were equipped with wax papers. Their capacitance have multiplied by a fator 3 to 4, letting the filters getting way out of their resonance frequencies, which led to a rather muddy sonic appearance of the organ.
It's better to stay away from any paper capacitors that aren't in a air and moisture tight envelope.

Best regards!
 
operater said:
I'm even more curios, would it be that risky to use them if they appear sealed physically?
You should not use them as traditional valve coupling caps (e.g. from anode to next grid), unless you value these caps more than you value your valves. The fact that the cap value has gone up (as I expected) shows that water is inside, which means that they will go leaky. Even if they don't leak, you will need to match values between channels if you want a stereo image.

As I said, bin them - or sell them to someone who has less sense than you! If you want to be honest you could tell potential customers that the value has changed. That will warn wise people to steer well clear of them.

mondogenerator said:
I dont see the value in Mustards or Vitamin Q either, just another vintage con.
At least Mustard caps are likely to still be good caps. Perfectly ordinary polyester caps, of course, so of no particular value except to people who don't understand electronics.
 
operater said:
I wouldn't go too far but caps are often most used as filters in a circuit and affect a significant portion of the frequency spectrum so they inherently have to color the sound with their imperfections and introduce at least some harmonics be it in parallel or as a coupling. Whether those changes are perceptible is strongly subjective but doesn't mean it's a con or that they are in-existent.
You are mixing reality, error and myth. Are you some sort of salesman?
 
Hi there Kay, thanks for input! This is exactly the case, many of them went up in value - they range from 138nF to 208nF but most are at 138-150nF. It's very interesting, I am curios now as to why paper waxes go up in value.

Best regards.

oprtr
Its a clue moisture has got into the things, water molecules have a very high dielectric constant.
 

operater

Member
2019-10-17 6:29 pm
Okay, many of you made great points here, but, I couldn't rest until I was done with this :zombie:. You deserve it !

[IMGDEAD]http://oprtr.win/shr/EFCO_wax_paper_leakage_test.JPG[/IMGDEAD]

The results are really interesting as most of the IR values are directly proportional to the rise in capacitance values yes.
However, as far as I understand ppl should chill a bit about vintage caps :cool: eh ? I mean all the doomsday and fireworx scenarios are really fun to read but... hey... What can possibly be disturbed by 10Mohms in any kind of a circuit whatsoever!?

Now the fun part: Who can guess whatssup with the first two caps in blue!? Whoever elaborates nicely on this first, gets a pair of those for christmas! Under the condition you honestly want to use them.

:santa3: Ho ho HO...hO
 

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