I’d say the first two had been sealed from the atmosphere somehow.
I may have some of the first chicken nuggets ever from under my car seat, maybe I should sell them on eBay!
I may have some of the first chicken nuggets ever from under my car seat, maybe I should sell them on eBay!
This whole thread has me thinking of an old Hammond organ my grandmother had.
At idle there would be this semi-continuous soft blumpity-blump noise that my dad figured was from an assortment of leaky capacitors in various stages. So may wax capacitors in that thing.
At idle there would be this semi-continuous soft blumpity-blump noise that my dad figured was from an assortment of leaky capacitors in various stages. So may wax capacitors in that thing.
13uA flowing in 500k grid resistance is 6V change of bias. This will throw a power tube into red-plate, or slam a preamp into not working at all.
Or "What can possibly be disturbed by 10Mohms in any kind of a circuit whatsoever!?" Well, you have a tube plate at 200V, and a next grid which should be at 0V with a 1 Meg grid resistor. 5Meg"1Meg divider is 1:0.167 ratio, so 200V arrives at 33V which is not 0V and likely to upset any tube we use.
If there is _NO_ DC voltage across the cap, such as a tone network, then indeed a 5Meg leak may do no harm. (However in a tone-net the >2:1 spread of values from nominal gives audible mis-tuning.) And switched tone-caps we often have to throw in a bunch of 3Meg resistors to avoid pops, and these caps are self-de-popped.
Did you wait a l-o-n-g time before reading? Say a minute? Reading DC leakage hastily puts you only partway down the infinite decay.
Or "What can possibly be disturbed by 10Mohms in any kind of a circuit whatsoever!?" Well, you have a tube plate at 200V, and a next grid which should be at 0V with a 1 Meg grid resistor. 5Meg"1Meg divider is 1:0.167 ratio, so 200V arrives at 33V which is not 0V and likely to upset any tube we use.
If there is _NO_ DC voltage across the cap, such as a tone network, then indeed a 5Meg leak may do no harm. (However in a tone-net the >2:1 spread of values from nominal gives audible mis-tuning.) And switched tone-caps we often have to throw in a bunch of 3Meg resistors to avoid pops, and these caps are self-de-popped.
Did you wait a l-o-n-g time before reading? Say a minute? Reading DC leakage hastily puts you only partway down the infinite decay.
The point you are missing (the author), is that an IR or 15MegOhms is not very good.
An IR of greater than 100M would be far more desirable.
To put that in perspective, I have checked vintage transformer (OPTs etc) that I salvage, and those with IRs <500M (certainly <250M) are fails.
There is a bit of 'wiggle room' but I'd have serious doubts about a winding with <100M)
(IR taken for 60s with 500V or 1000V range on Megger MIT410). Standard practice
If they fail that test, I will not sell them on to another.
Transformers are a little different, in that you can warm them up and drive out moisture from the windings, and improve IR by a large margin (as long as it isnt paper and wax insulated!)
An IR of greater than 100M would be far more desirable.
To put that in perspective, I have checked vintage transformer (OPTs etc) that I salvage, and those with IRs <500M (certainly <250M) are fails.
There is a bit of 'wiggle room' but I'd have serious doubts about a winding with <100M)
(IR taken for 60s with 500V or 1000V range on Megger MIT410). Standard practice
If they fail that test, I will not sell them on to another.
Transformers are a little different, in that you can warm them up and drive out moisture from the windings, and improve IR by a large margin (as long as it isnt paper and wax insulated!)
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Hi All, thanks again for all the comments. May I first remind you that I never came here to sell those caps. I am very curious about electronics in general and love audio. I have restored a couple of SolidStates in the past and only built my first tube amp from a DIY kit a couple of months ago. I love to tweak that thing and I love the sound of hot biased EL34s in a SET config paired with some Klipsch speakers. When I say hot I mean near 100% cathode bias 😀 (I already feel I'll be getting burned at a stake by some😛) but I sincerely think some are missing out big on the tone character when underbiased in class A operation.
Back to the caps:
@phase no, the two caps in blue were actually used in that amp for about 30hours.
Those measurements demonstrate the self healing properties of paper wax magnificently. I am wondering if the reforming process would benefit from some more time hmm.
@daqvin_carter Beautiful noise <3 noise is love!!
Not a very bohemian thing to do now, is it ?
@PRR Scary point there about the bias. My 6SN7s didn't present any distress, I could watch those voltages, but I'm not sure I follow how you end up with 33V on the grid? There's not that much current between B+ and the next grid.
I did wait for about a minute, or until the decay slowed down when measuring.
Anyone knows the default IR values for a brand new paper wax cap like one of those jupiters or smtn ?
Best.
Back to the caps:
@phase no, the two caps in blue were actually used in that amp for about 30hours.
Those measurements demonstrate the self healing properties of paper wax magnificently. I am wondering if the reforming process would benefit from some more time hmm.
@daqvin_carter Beautiful noise <3 noise is love!!
Not a very bohemian thing to do now, is it ?
@PRR Scary point there about the bias. My 6SN7s didn't present any distress, I could watch those voltages, but I'm not sure I follow how you end up with 33V on the grid? There's not that much current between B+ and the next grid.
I did wait for about a minute, or until the decay slowed down when measuring.
Anyone knows the default IR values for a brand new paper wax cap like one of those jupiters or smtn ?
Best.
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Paper Wax capacitors have not been manufactured for many decades so no point asking about values and leakage.
I have been in the electronics industry professionally since 1967 and everytime I see a Paper Wax capacitor it is automatically replaced with MKP or polystyrene type for reliability. The only good use for the wax that we found oozing out of many makers capacitors was on the end of a screwdriver blade to remove non ferrous screws from awkward places.
I have been in the electronics industry professionally since 1967 and everytime I see a Paper Wax capacitor it is automatically replaced with MKP or polystyrene type for reliability. The only good use for the wax that we found oozing out of many makers capacitors was on the end of a screwdriver blade to remove non ferrous screws from awkward places.
No self-healing taking place. Self-healing relates to voltage spikes, not leakage due to moisture. The two caps showing slightly better results are due to being warmed a bit in the equipment. However, they are still of 'bin quality', like all the rest. You will not be able to drive off enough moisture to make the caps usable as coupling caps. As they are significantly off-value they cannot be seriously used as filter caps. Bin them all - this is what should happen to almost any old caps with paper dielectric (apart perhaps from a few military spec hermetically sealed ones, but even they are still only caps at the end of the day).operater said:
Thank goodness for some sense.
My reference to standard testing processes for windings and typical fail values for IR were conveniently ignored by the OP.
Hundreds if not thousands of MegOhms IR is typical for a good capacitor/winding.
I.e. these paper wax caps are shot.
Obviously a troll post by the OP seeing as the account is very new, as is the ebay link to the capacitors in question.
Maybe he will find an idiot to buy them. Certainly that is one seller I'll be blocking on ebay!
So what are "Erectrical Characteristics"
I saw that but didn't think it worthy of a
I am always astonished that Asian makers don't rent an out-of-work American/British journalist to proof their texts. Panasonic could afford several. The small shops could send text to a service agency for native-English proofreading.
You are either the salesman (how come you have so many of the exact product being offered on sale?), or a shill for him, same thing.
Yes, at an abandoned warehouse, flooded basement or street corner junkbin.
Or you bought them for $5 the lot of 100 , "as is", "no returns accepted"
Of course, you instantly thought about some Mojo Head who might exchange hard earned cash for a few of them.
Just the very ad starts lying 😡 :
you show higher spread ... and that if we can trust your measurements.
How can you "match" parts which change value just on climate?
meaning temperature and humidity.
So useless that you can´t even try the old joke of charging them to significant voltage and leaving them on a table so unaware people catch them and get a shock ... because they will self discharge in seconds 😛
Hey, not all is lost, grab your hippy roundnose pliers and in minutes you can turn them into Art:
+-20% is not an ad it is the factory spec as written on the caps, however the value drifts are clearly stated! As for the salesman/shill part, you just keep forgetting that I didn't advertise those caps here as being sold on ebay in the first place.
Also, thinking I don't have better things to do besides faking capacitor measurements is borderline schizophrenic
Second, all the scorn and critic regarding those caps and yet hardly anyone is able to produce original IR values for those types of caps back at the time. I was hoping to find some original IR values so I can compare them to this batch.
What I am trying to argue here is that vintage audio is not about nitpicking modern component specs, turning the stuff inside out and replacing everything with modern low tolerance electronics. Actually it is kinda sinful from my point of view!!
Oh, and, no, your world is not gonna explode because of some drifts in values here and there - probably not even the amplifier for that matter.
Why is it so hard to handle a little bit of uncertainty in today's world ? Why are we all so obsessed with security and safety ? Where's the Rock and Roll ? WHERE'S THE SPIRIT ?
A while back there seemed to be talk among musicians expressing interest in old bumblebee caps - 0.022uf I believe - and how they were "all the rage" for guitar amps for their "smooth vintage sound".
Made me laugh, because I know better - it sounded like someone trying to get rich off old parts - spread the word around and hope for the best.
They'll sell anything online these days. 😱
Made me laugh, because I know better - it sounded like someone trying to get rich off old parts - spread the word around and hope for the best.
They'll sell anything online these days. 😱
With leakage at the level those caps are showing, a use would be better off using an electrolytic capacitor, costing $0.1
Drifts in value, are completely undesirable for anyone wanting to use as coupling capacitor, since the variation is wide, no confidence in the RC frequency remaining as designed (which is the point, entirely)
Any use at, or close to the OEM rated voltage, is risky, if the user values the longevity of the valves in his/her circuit.
There is no tone advantage worth pursuing at the expense of valve lifetime, justifiable by a $20 POS capacitor.
Modern IR values for capacitors arent all that much different from those OLD ones - choose to ignore, as you will, but anything less than 100Meg and they're junk.
Nothing to gain here, besides circuit failure and some irate customers.
We have told you facts. You clearly don't like the facts.operater said:
In post 1 you asked us what we think. We have told you. You may have expected us to praise you for your good luck/wisdom in stumbling across such a wonderful cache of highly-prized audio capacitors, but unfortunately we have had to inform you that what you have is merely old junk which should be binned. Maybe you were planning to use our praise in your advertising?operater said:
No you are not. You are arguing that old junk is good for audio circuits. You are mistaken. Old junk can ruin a circuit, not because it is old but because it is junk.operater said:
Let us suppose that these caps were in good condition and not leaky, and were still close to their stated capacitor values. Even then they would still be ordinary caps, of relatively poor tolerance (20%), so would not work any better than any modern cap as a coupling cap.
OK, you might have enough money to risk damaging your valves by using caps known to be leaky. Up to you. But what is the point of using a known faulty component? Doing that is not "Rock and Roll", it is merely stupid.operater said:
Would you use a bike made of heavily rusted bent old bits of steel from a scrapyard? Or would you expect it to bend, break and generally be a pain in the proverbial? Same difference here, the parts have rotted, nothing glamorous about that.
I don't know what to say people. I want you all to know that I am deeply humbled by your participation in this thread. Honestly I'm quite new with this, and I'm really glad to be here.
Guess I was not aware that 30µA of current leak can pose such a risk and liability as signal coupling in a tube amplifier, or can it actually!? Let's forget about nitpicking values for just an instant. What is the real operational risk here ? Anyone has any examples of wax paper actually shorting and slamming an output stage of a tube amp, and what are the odds for that ?
Please bearrr with me for a bit more! Let's get a bit technical once again:
Thanks PRR but when we try and simulate this here is what happens:
No leak:
Yes leak:
Also those 6V of leakage being itself @ 13µA cannot affect bias by 6V since the plate current is much higher. There is no way this measly 13µAmps can do anything at all to a plate running at 1 053 000 µAmps. Also, the grid stopper can conveniently drown away even higher leakages before they ever reach the grid itself.
See how I deliberately took a low plate current tube operating points such as 12AX7 to demonstrate this. Higher current plates would care even less about such a leak.
You can check it out on falstad yourself (pay attention to the simulation time as it takes some time for the values to settle):
http://tinyurl.com/yyqyqfmq
The sim is done with 0 input signal as it doesn't matter at all in class A cathode biased operation anyway. All the tubes are configured for their respective mu values.
So the real worry here is can this leakage get worse and short the cap ? Honestly I don't see how. Leaking even 30µA @ 300V that's like 9mW dissipation! How is that ever gonna break the cap or have the internal components melt or degrade ? Not to mention that the current leak is trending downwards with time of operation.
Tell you what! I'm gonna slam couple of those in parallel with some power supply filter caps @ 270V and let them sit there for couple of months and see where they get with the values!
Best.
oprtr
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Why in the world would you compare transformer windings and capacitors ? Their internal structures and ways of operation differ by orders of magnitude! Why ever do that ??
Dielectric material/insulation is not the same ! Plate separation in caps can get insanely low when compared to the distance between wound wires! So there goes your insulation thickness.
The way the energy is stored in caps is not the same either! Basically nothing is same! No one here needs to be reminded of how each of those passive components work.
It is absolutely logical that a transformer should have far lower IR values than capacitors! Also different type capacitors should have very different tendencies in developing current leaks. I'd never compare a tightly wound paper cap to an electrolytic one either.
Guess the wax paper's hygroscopic nature is it's inevitable leaky destiny. But, the question remains, what components that operate in ranges of miliamps care about a few micro-amps of leakage if any do at all?
I am not arguing that values of those caps are great, but whether any kind of a circuit example really cares about such a low current leaking!
Just like in the example above.
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