What type of capacitor should I use?

What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?

I am not referring to the electrolytics, those I know need to be
electrolytic caps. I am referring to the inter stage caps, such as .01
..05 .1, .005 and so on.....

The object is to replace all the caps in an old tube radio, or any other
tube stuff.

Yes, I know this topic was sort of discussed a few weeks ago, and I
recall hearing that any of them would work, but that does not really
answer this question. Sure, they may all work, but what type would be
the closest match to the original paper/wax types?

From what I know, those caps were made from paper and a metal foil
rolled up and coated with wax. So, what is the nearest similar type?

From that last discussion, I know I left that thread sort of puzzled
because all caps seem tp contain "poly" (which means plastic). I am
thinking that what seems to be the closest would be whatever plastic
replaces the paper, and a foil. From what I understand, some caps do not
have a foil, but rather some sort of metallic material that is coated or
sprayed on. Those are probably not what I would want to use, because
they are not similar to the originals.

I am fully aware that the voltage MUST be the same or higher and the uf
must be close, such as .047 to replace .05. Also for tube circuits,
axial leads are preferred.

Then too, looking on ebay and other sources, I see a lot of very
expensive caps which are intended for high end audio amps. For my needs,
I will not pay $29.99 for one cap, and yes I have seen them cost that
much.

I am seeing some no-name cheap China caps selling for as little as 20
cents each. While I like to save money, I'd really rather spend $1 each
for something like the Orange Drops, which have been around a long time
and seem to be good quality, despite the fact they dont come in axial
form. But they generally can fit into most places.

I will only be replacing those paper/wax caps and the electrolytics. I
wont touch any mica or silver mica types, unless they appear to be bad
(I will probably test them though).

One that I do recall, are the so called Mylar, which I think were the
first ones that were made to replace the old paper caps. I guess they
now changed that name to something "poly" also.....

What would you recommend or use?
Web url's appreciated for lower cost AMERICAN made caps.

One last thing, I found some cap assortments on ebay. 150 or 200 caps of
assorted values, labeled as NOS (New old stock), but they are NOT the
paper/wax kind. Since I have no spare caps, and just want an assortment
on hand, I was thinking about buying one of those. I would NOT buy NOS
electrolytics, but for the interstage types, I might consider this, just
so I have an assortment of caps on hand..

 

[Trevor Wilson]

On 10/03/2017 12:01 PM, oldschool@tubes.com wrote:

What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?

I am not referring to the electrolytics, those I know need to be
electrolytic caps. I am referring to the inter stage caps, such as .01
.05 .1, .005 and so on.....

The object is to replace all the caps in an old tube radio, or any other
tube stuff.

Yes, I know this topic was sort of discussed a few weeks ago, and I
recall hearing that any of them would work, but that does not really
answer this question. Sure, they may all work, but what type would be
the closest match to the original paper/wax types?

From what I know, those caps were made from paper and a metal foil
rolled up and coated with wax. So, what is the nearest similar type?

From that last discussion, I know I left that thread sort of puzzled
because all caps seem tp contain "poly" (which means plastic). I am
thinking that what seems to be the closest would be whatever plastic
replaces the paper, and a foil. From what I understand, some caps do not
have a foil, but rather some sort of metallic material that is coated or
sprayed on. Those are probably not what I would want to use, because
they are not similar to the originals.

I am fully aware that the voltage MUST be the same or higher and the uf
must be close, such as .047 to replace .05. Also for tube circuits,
axial leads are preferred.

Then too, looking on ebay and other sources, I see a lot of very
expensive caps which are intended for high end audio amps. For my needs,
I will not pay $29.99 for one cap, and yes I have seen them cost that
much.

I am seeing some no-name cheap China caps selling for as little as 20
cents each. While I like to save money, I'd really rather spend $1 each
for something like the Orange Drops, which have been around a long time
and seem to be good quality, despite the fact they dont come in axial
form. But they generally can fit into most places.

I will only be replacing those paper/wax caps and the electrolytics. I
wont touch any mica or silver mica types, unless they appear to be bad
(I will probably test them though).

One that I do recall, are the so called Mylar, which I think were the
first ones that were made to replace the old paper caps. I guess they
now changed that name to something "poly" also.....

What would you recommend or use?
Web url's appreciated for lower cost AMERICAN made caps.

One last thing, I found some cap assortments on ebay. 150 or 200 caps of
assorted values, labeled as NOS (New old stock), but they are NOT the
paper/wax kind. Since I have no spare caps, and just want an assortment
on hand, I was thinking about buying one of those. I would NOT buy NOS
electrolytics, but for the interstage types, I might consider this, just
so I have an assortment of caps on hand..

**Just use a decent quality Mylar, polycarb or polyprop cap. If you try
to source PIO (Paper In Oil) types, then you'll need the national debt
of a small South American nation to pay for one. AND you'll gain
nothing. Just a plain ole plastic cap. It'll work and keep working and
there will be zero impact on sound quality.

--
Trevor Wilson
www.rageaudio.com.au

 

[Foxs Mercantile]

On 3/9/2017 7:01 PM, oldschool@tubes.com wrote:

What type of capacitor would be the best match to replace
the old paper/wax caps in old tube gear?

Were you NOT paying attention previously when we ALL told
you to use the yellow plastic caps? 630 volt.

<http://www.tuberadios.com/capacitors/>

Or are you just being stubborn?

Paper dielectric capacitors are crap. They ALL need to be
replaced. Trying to "just replace the bad ones" is a fool's
errand. They're all bad or will fail after they're "back
in service" again.

I have a Collins R-390A receiver on the bench. It's full of
paper capacitors. The IF module alone had 18 of them. They
have all been replaced.
"But it's Collins" and "Those were mil-spec" and and and
every other excuse for not changing them. Changing them made
a profound difference in how well the radio works.

These parts are bad. Anyone that tells you otherwise is
either lying to you or is delusional.


--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

 

[tom]

<oldschool@tubes.com> wrote in message
news:43t3cc9j919psgj3l1jiqerqdcvdd7jo84@4ax.com...

What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?


One that I do recall, are the so called Mylar, which I think were the
first ones that were made to replace the old paper caps. I guess they
now changed that name to something "poly" also.....

Mylar is DuPont's brand name for a stretched PET plastic. P is for poly

 

On Friday, March 10, 2017 at 5:05:33 AM UTC-5, olds...@tubes.com wrote:

But I see no reason to change those small caps (.05 .001, etc). Not for
the brief times thay are used. and they are all very accurate in their
values.

I have tons of new old stock caps that I keep for nostalgia reasons (dad's), but if I place them on my LC75 and run working voltages into them, most of them will draw excessive current and never "reform". Most are also wildly (by today's standards) off value. I don't know if they drifted over time or if they're typically that far off when new.

Of all the mistakes you made in your rant, the biggest is confusing Walmart Chinese products with individual components. Unless you have a natural racist bent, be aware that having Chinese DNA does not preclude one from making quality or innovative assemblies or components as needed.

When rebuilding a 50 year old radio, we find many original caps inside. Very few can pass a voltage test, and really, when is the last time these radios were used daily? 30 or more years ago? Most of the old radios you will find to restore haven't been used in decades. Those paper caps were shot long ago even if the circuit still struggles to life with them.

 

[pfjw@aol.com]

A few things:

Today, capacitors are commodities. Meaning that the technology involved in making them is fully established, well understood, extremely reliable and (now) very simple. Meaning, again, that the lowest-cost producer making a generic product will pretty much win the market. Meaning (a third time), that the cost of 'faking' such a device will likely approach or exceed the cost of making the proper product in the first place.

So, those capacitors that require very little technology - small-value film caps, for instance - will be cheap and plentiful. And, apart from very specific requirements - aerospace, medical, ultra-precision and similar - there is no reason to choose one item over another from one source over another as, at that level, they are all pretty much from the same place.

Electrolytics do have a greater variation, include different technologies, different chemistry, materials and such, have many different applications, and sub-categories within those applications. With that in mind, one may choose from different sources.

Specialty caps are a different matter altogether, and unless one is in the Aerospace, medical, ultra-precision or similar industries, not really relevant to vintage equipment. Russian PIO caps presently in vogue with the audio hobby are a case in point. Utterly silly indulgences but plenty of yiches..

Meaning that unless you wish to pay aerospace prices, purchase the item that meets the needs at the best price from a *RELIABLE* supplier. *RELIABLE* supplier will protect you from counterfeits - usually at a very small premium, but well worth it. And if that part happens to be from China, comfort yourself that it is due to the commoditization of the product - and your preferred suppliers simply cannot make a profit in that line. The bottom line is that your vintage item is singing again, far more reliable than it ever was in the past, and, very likely far into the future.

One example: I pay about $1.75 extra per transistor from Mouser than for the same part-number from another supplier. Why? Mouser is a major contributor and founder of anti-counterfeit parts organizations.

https://en.wikipedia.org/wiki/Mouser_Electronics

If Mouser sells me a part, I feel pretty sure it will be as represented, whatever the country of origin. Yes, I tend to hold my nose and grumble, if that is China. But increasingly often, the alternative is nothing at all, or old-stock material no better than what is being replaced.

Does your meter test those caps and resistors at any sort of operating voltage? Before you describe them as 'very accurate', they must be tested at operating voltages.

Peter Wieck
Melrose Park, PA

 

On Thu, 9 Mar 2017 20:17:16 -0600, Foxs Mercantile <jdangus@att.net>
wrote:

On 3/9/2017 7:01 PM, oldschool@tubes.com wrote:
What type of capacitor would be the best match to replace
the old paper/wax caps in old tube gear?

Were you NOT paying attention previously when we ALL told
you to use the yellow plastic caps? 630 volt.

I WAS paying attention and I even contacted that seller and found out
they are made in China.

http://www.tuberadios.com/capacitors/

Or are you just being stubborn?

No, not being stubborn , I just dont want caps made in China. Not much
of anything made in China is a quality item. That seller has good prices
and a fair selection, but I still dont want China caps, which will
likely contain duds, and I'll end up replacing all of them in 5 years or
less, again.

And that site dont give enough info to translate to other sites. They
are just called "Axial Film Capacitors" on that site. When I look at
other sites, I see them sold with some sort of "poly" name, and I see
the word "film" used, as well as "foil". So, what do these compare to in
the words used to sell other brands?

That word "film" bothers me, anyhow. Just what the heck is this film? Is
it just some sprayed on metalic particles? The old paper caps contained
foil, which to me means something that looks like tin foil used in the
kitchen. Maybe I'm wrong, but if my radio or (whatever) was designed for
caps made with foil, I'd prefer to use caps with foil, and whatever
plastics they used to replace the paper. In other words, I want caps
that most closely mimic the original caps, except without the paper.

Paper dielectric capacitors are crap. They ALL need to be
replaced. Trying to "just replace the bad ones" is a fool's
errand. They're all bad or will fail after they're "back
in service" again.

Those paper caps may be crap now, but considering many of them lasted 50
years, they were not all crap, to last that long. I doubt any China made
caps will last even close to 50 years. I may be wrong, but based on
nearly all China products, I doubt any of them will last 5 years.
Everything made in China is just throw away short lived junk. Made to
fail one day after their warranty expires.

I have a Collins R-390A receiver on the bench. It's full of
paper capacitors. The IF module alone had 18 of them. They
have all been replaced.
"But it's Collins" and "Those were mil-spec" and and and
every other excuse for not changing them. Changing them made
a profound difference in how well the radio works.

I'm sure it did make a difference to the better, but for how long?

But rather that toss out my opinion, which is based on my overall
feelings about China products, you tell me how these caps have worked
for you. (assuming they are what you have used).
What precentage of them have been duds? If you have tested them, how
accurate are they? Have you had any fail? How long have you used them?
Will they really handle the max voltage they are rated as? How do they
perform under heat and other extremes? DId your Collins work as
designed, or did you have to re-align it or do any modifications because
the caps are not the "foil" type, and thus are not what the circuit was
made to use?

Sellers (of anything), always rate their goods at "Top Quality", but
advertising is mostly all lies. I want references from you, and anyone
else who is NOT connected to the seller.

These parts are bad. Anyone that tells you otherwise is
either lying to you or is delusional.

Although this is drifting from the topic, I just bought an old Sencor
Substitution box. It's for Resistance, Capacitors, (including lytics),
one silicone and one selenium diode, and a few other features. I took a
modern VOM with capacitor tester, and found all the paper/wax caps in
that box are still very accurate. However some of the lytics are not
even close. The resistors are all close too. Considering these parts
have seen little voltage and use, I see no reason to change any of the
small caps or the resistors. I do plan to change the electrolytics
though, because I know they deteriorate just from age, whether they are
used or not, because of the chemicals in them. (and my tests confirm
they are not even close to their rated UF values, some as much as 50%
off.

But I see no reason to change those small caps (.05 .001, etc). Not for
the brief times thay are used. and they are all very accurate in their
values.

 

[pfjw@aol.com]

On Friday, March 10, 2017 at 11:31:08 AM UTC-5, Dan wrote:

Give this site a try.

https://www.tedss.com/LearnMore/American-Made-Capacitors

Until you go into their product list and find all of the 'usual suspects' from the 'usual sources'.

https://www.tedss.com/Catalog/Browse?searchString=NIC&inCategory=ALUMINUM%20ELECTROLYTIC%20%3E%20AXIAL%20%3E%20HIGH%20TEMP

The (very, very) few US-origin film caps offered are either extremely expensive, low-voltage, of unusual values (5.5 uF film? Really?) or all three.

Seriously, there is no 'there' there.

Peter Wieck
Melrose Park, PA

 

[analogdial]

Dan wrote:

Give this site a try.

https://www.tedss.com/LearnMore/American-Made-Capacitors

Right on the first page:

"Think all capacitors made in the Far East are cheap, noisy, low
quality."

'If you are looking for quality components, then TEDSS.com is for YOU.'

"Americans put a man on the moon in 1969 with American-made capacitors.
The greatest military power in the world was made by using High Quality
American Made apacitors."


Wow. I suppose the grammar and spelling are about what you'd expect
from a Usenet loon, but subpar for a vendor trying to sell quality.

And, for what it's worth, I DON'T think ALL capacitors made in the Far
East are cheap, noisy, low quality. And as soon as I hear that the
Chinese have mastered the art of making "High Quality apacitors.", I'll
be doubling up on my Mandarin lessons.

 

[Foxs Mercantile]

On 3/10/2017 4:04 AM, oldschool@tubes.com wrote:

On Thu, 9 Mar 2017 20:17:16 -0600, Foxs Mercantile wrote:
Or are you just being stubborn?

No, not being stubborn , I just dont want caps made in China.
Not much of anything made in China is a quality item.
That seller has good prices and a fair selection, but I still
don't want China caps, which will likely contain duds, and
I'll end up replacing all of them in 5 years or less, again.

Ok, how about willfully ignorant or xenophobic.

Maybe I'm wrong, but if my radio or (whatever) was designed
for caps made with foil, I'd prefer to use caps with foil, and
whatever plastics they used to replace the paper. In other
words, I want caps that most closely mimic the original caps,
except without the paper.

Which shows a complete and total misunderstanding of what
capacitors are.

Those paper caps may be crap now, but considering many of them
lasted 50 years, they were not all crap, to last that long.

Many? Of the billions that were produced between 1935 and 1965
Almost all of them have failed. The few that "might still be
good" are statistically zero.

I doubt any China made caps will last even close to 50 years.
I may be wrong, but based on nearly all China products, I
doubt any of them will last 5 years.
Everything made in China is just throw away short lived junk.
Made to fail one day after their warranty expires.

More willful ignorance on display.

But rather that toss out my opinion, which is based on my
overall feelings about China products, you tell me how these
caps have worked for you. (assuming they are what you have
used).

There's that magic word "feelings" again. Based on nothing.

What percentage of them have been duds? If you have tested
them, how accurate are they? Have you had any fail? How long
have you used them?

I have been using them since 1994 when I got back into vintage
radios and test equipment after retiring. 23 years now. I have
never had a failure of any of the yellow plastic capacitors.

Will they really handle the max voltage they are rated as?
How do they perform under heat and other extremes?

Yes and flawlessly.

Did yourCollins work as designed, or did you have to re-align
it or do any modifications because the caps are not the "foil"
type, and thus are not what the circuit was made to use?

Other than some expected drift due to aging components little or
no alignment, other than "touch up" was required. This was done
to make the radio "work as specified" not just "it works."

You still completely misunderstand how capacitors work.

I just bought an old Sencor Substitution box.
I took a modern VOM with capacitor tester, and found all the
paper/wax caps in that box are still very accurate.

That is NOT a comprehensive test. It says nothing about leakage
or the probability of failure with applied voltage.

But I see no reason to change those small caps (.05 .001, etc).
Not for the brief times they are used. and they are all very
accurate in their values.

More willful ignorance to justify your position.

This is like assuming your tires are safe, even though you have
to put air in them every time you wish to drive your vehicle.

If you'll pardon the pun, to recap, I've been doing this for 23
years as a source of income. I haven't had ANY radios come back
due to failures of the "cheap Chinese crap" capacitors as you
insist on calling them.



--
Jeff-1.0
wa6fwi
http://www.foxsmercantile.com

 

[Ralph Mowery]

In article <a7dd2134-3369-fee3-beed-722ec1c4a3b9@att.net>,
jdangus@att.net says...

This is like assuming your tires are safe, even though you have
to put air in them every time you wish to drive your vehicle.

Speaking of unsafe tires, they do seem to have a limiated lifetime even
if not used very much. Friend jsut went through that with a tire
company. He had a tire that is starting to seperate. He talked with
the tire maker. While the tire had plenty of thread and mileage let on
it, it was over 7 years old. The company told him that after abut 5 to
6 years many tires will just go bad. In a way I wish that I had been
aware of that a year or two ago. I am retired and do not drive that
much and have a car and truck. I put some tires on them that was rated
very high in the milage thinking I would not have to worry about tires
for a long time, but seems that they may age out with over half the
thread left on them.

Speaking of China. They make some items that seem to be as good as
any,and they make a lot of junk. I have several pieces of equipmant
from China that seems to be as good as any. Friend ordered some
transistors and all of them were bad junk that did not even test on a
transistor tester.

As many power tubes are not made in the US anymore a company contractes
with a China company to make some. They seem to hold up very well.

 

[Dan]

Give this site a try.

https://www.tedss.com/LearnMore/American-Made-Capacitors


<oldschool@tubes.com> wrote in message
news:43t3cc9j919psgj3l1jiqerqdcvdd7jo84@4ax.com...

What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?

I am not referring to the electrolytics, those I know need to be
electrolytic caps. I am referring to the inter stage caps, such as .01
.05 .1, .005 and so on.....

The object is to replace all the caps in an old tube radio, or any other
tube stuff.

Yes, I know this topic was sort of discussed a few weeks ago, and I
recall hearing that any of them would work, but that does not really
answer this question. Sure, they may all work, but what type would be
the closest match to the original paper/wax types?

From what I know, those caps were made from paper and a metal foil
rolled up and coated with wax. So, what is the nearest similar type?

From that last discussion, I know I left that thread sort of puzzled
because all caps seem tp contain "poly" (which means plastic). I am
thinking that what seems to be the closest would be whatever plastic
replaces the paper, and a foil. From what I understand, some caps do not
have a foil, but rather some sort of metallic material that is coated or
sprayed on. Those are probably not what I would want to use, because
they are not similar to the originals.

I am fully aware that the voltage MUST be the same or higher and the uf
must be close, such as .047 to replace .05. Also for tube circuits,
axial leads are preferred.

Then too, looking on ebay and other sources, I see a lot of very
expensive caps which are intended for high end audio amps. For my needs,
I will not pay $29.99 for one cap, and yes I have seen them cost that
much.

I am seeing some no-name cheap China caps selling for as little as 20
cents each. While I like to save money, I'd really rather spend $1 each
for something like the Orange Drops, which have been around a long time
and seem to be good quality, despite the fact they dont come in axial
form. But they generally can fit into most places.

I will only be replacing those paper/wax caps and the electrolytics. I
wont touch any mica or silver mica types, unless they appear to be bad
(I will probably test them though).

One that I do recall, are the so called Mylar, which I think were the
first ones that were made to replace the old paper caps. I guess they
now changed that name to something "poly" also.....

What would you recommend or use?
Web url's appreciated for lower cost AMERICAN made caps.

One last thing, I found some cap assortments on ebay. 150 or 200 caps of
assorted values, labeled as NOS (New old stock), but they are NOT the
paper/wax kind. Since I have no spare caps, and just want an assortment
on hand, I was thinking about buying one of those. I would NOT buy NOS
electrolytics, but for the interstage types, I might consider this, just
so I have an assortment of caps on hand..

 

[Tom Biasi]

On 3/9/2017 9:17 PM, Foxs Mercantile wrote:

Were you NOT paying attention previously when we ALL told
you to use the yellow plastic caps? 630 volt.

Thanks for the reminder Jeff. I need some caps from Sal.

 

[Jim Mueller]

On Fri, 10 Mar 2017 18:04:32 +0000, analogdial wrote:

Dan wrote:

Give this site a try.

https://www.tedss.com/LearnMore/American-Made-Capacitors


Right on the first page:

"Think all capacitors made in the Far East are cheap, noisy, low
quality."

'If you are looking for quality components, then TEDSS.com is for YOU.'

"Americans put a man on the moon in 1969 with American-made capacitors.
The greatest military power in the world was made by using High Quality
American Made apacitors."


Wow. I suppose the grammar and spelling are about what you'd expect
from a Usenet loon, but subpar for a vendor trying to sell quality.

And, for what it's worth, I DON'T think ALL capacitors made in the Far
East are cheap, noisy, low quality. And as soon as I hear that the
Chinese have mastered the art of making "High Quality apacitors.", I'll
be doubling up on my Mandarin lessons.

And if you look at their listings, the capacitors are made by a mix of
manufacturers, some that I've heard of, some not. It appears that they
are a surplus house.

--
Jim Mueller wrongname@nospam.com

To get my real email address, replace wrongname with dadoheadman.
Then replace nospam with fastmail. Lastly, replace com with us.

 

[whit3rd]

On Friday, March 10, 2017 at 2:05:33 AM UTC-8, olds...@tubes.com wrote:

No, not being stubborn , I just dont want caps made in China. Not much
of anything made in China is a quality item.

If "the quality" is capacitance, or leakage current, or standoff voltage,
or self-resonant frequency, or series resistance, the radio cares.

It doesn't care about 'made in China'.

 

[Big Bad Bob]

On 03/09/17 17:01, oldschool@tubes.com wrote:

What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?

I am not referring to the electrolytics, those I know need to be
electrolytic caps. I am referring to the inter stage caps, such as .01
.05 .1, .005 and so on.....

The object is to replace all the caps in an old tube radio, or any other
tube stuff.

well, if you must replace them with more modern components, a decent
ceramic capacitor should do fine. From what I have seen, ceramics were
common in gear made in the 50's and 60's because of their small relative
size and reasonable consistency in manufacturing.

You should be able to order them from companies like Digikey, Mouser,
etc.. Just make sure the voltage ratings are high enough, and you
should be ok.

I've seen on-line "photo piles" of before/after restoration efforts in
which modern components were "hidden" inside of hollowed-out components.
Maybe you can stash a modern ceramic inside of the paper/wax tube, and
seal it up with a bit of hot glue...

 

On Friday, 10 March 2017 10:05:33 UTC, olds...@tubes.com wrote:

On Thu, 9 Mar 2017 20:17:16 -0600, Foxs Mercantile <jdangus@att.net
wrote:

On 3/9/2017 7:01 PM, oldschool@tubes.com wrote:
What type of capacitor would be the best match to replace
the old paper/wax caps in old tube gear?

Were you NOT paying attention previously when we ALL told
you to use the yellow plastic caps? 630 volt.

I WAS paying attention and I even contacted that seller and found out
they are made in China.

http://www.tuberadios.com/capacitors/

Or are you just being stubborn?

No, not being stubborn , I just dont want caps made in China. Not much
of anything made in China is a quality item. That seller has good prices
and a fair selection, but I still dont want China caps, which will
likely contain duds, and I'll end up replacing all of them in 5 years or
less, again.

And that site dont give enough info to translate to other sites. They
are just called "Axial Film Capacitors" on that site. When I look at
other sites, I see them sold with some sort of "poly" name, and I see
the word "film" used, as well as "foil". So, what do these compare to in
the words used to sell other brands?

That word "film" bothers me, anyhow. Just what the heck is this film? Is
it just some sprayed on metalic particles? The old paper caps contained
foil, which to me means something that looks like tin foil used in the
kitchen. Maybe I'm wrong, but if my radio or (whatever) was designed for
caps made with foil, I'd prefer to use caps with foil, and whatever
plastics they used to replace the paper. In other words, I want caps
that most closely mimic the original caps, except without the paper.


Paper dielectric capacitors are crap. They ALL need to be
replaced. Trying to "just replace the bad ones" is a fool's
errand. They're all bad or will fail after they're "back
in service" again.

Those paper caps may be crap now, but considering many of them lasted 50
years, they were not all crap, to last that long. I doubt any China made
caps will last even close to 50 years. I may be wrong, but based on
nearly all China products, I doubt any of them will last 5 years.
Everything made in China is just throw away short lived junk. Made to
fail one day after their warranty expires.

I have a Collins R-390A receiver on the bench. It's full of
paper capacitors. The IF module alone had 18 of them. They
have all been replaced.
"But it's Collins" and "Those were mil-spec" and and and
every other excuse for not changing them. Changing them made
a profound difference in how well the radio works.

I'm sure it did make a difference to the better, but for how long?

But rather that toss out my opinion, which is based on my overall
feelings about China products, you tell me how these caps have worked
for you. (assuming they are what you have used).
What precentage of them have been duds? If you have tested them, how
accurate are they? Have you had any fail? How long have you used them?
Will they really handle the max voltage they are rated as? How do they
perform under heat and other extremes? DId your Collins work as
designed, or did you have to re-align it or do any modifications because
the caps are not the "foil" type, and thus are not what the circuit was
made to use?

Sellers (of anything), always rate their goods at "Top Quality", but
advertising is mostly all lies. I want references from you, and anyone
else who is NOT connected to the seller.

These parts are bad. Anyone that tells you otherwise is
either lying to you or is delusional.

Although this is drifting from the topic, I just bought an old Sencor
Substitution box. It's for Resistance, Capacitors, (including lytics),
one silicone and one selenium diode, and a few other features. I took a
modern VOM with capacitor tester, and found all the paper/wax caps in
that box are still very accurate. However some of the lytics are not
even close. The resistors are all close too. Considering these parts
have seen little voltage and use, I see no reason to change any of the
small caps or the resistors. I do plan to change the electrolytics
though, because I know they deteriorate just from age, whether they are
used or not, because of the chemicals in them. (and my tests confirm
they are not even close to their rated UF values, some as much as 50%
off.

But I see no reason to change those small caps (.05 .001, etc). Not for
the brief times thay are used. and they are all very accurate in their
values.

Your assumptions are wrong


NT

 

[Michael A. Terrell]

Big Bad Bob wrote:

On 03/09/17 17:01, oldschool@tubes.com wrote:
What type of capacitor would be the best match to replace the old
paper/wax caps in old tube gear?

I am not referring to the electrolytics, those I know need to be
electrolytic caps. I am referring to the inter stage caps, such as
.01 .05 .1, .005 and so on.....

The object is to replace all the caps in an old tube radio, or any
other tube stuff.

well, if you must replace them with more modern components, a decent
ceramic capacitor should do fine. From what I have seen, ceramics
were common in gear made in the 50's and 60's because of their small
relative size and reasonable consistency in manufacturing.

You should be able to order them from companies like Digikey, Mouser,
etc.. Just make sure the voltage ratings are high enough, and you
should be ok.

I've seen on-line "photo piles" of before/after restoration efforts in
which modern components were "hidden" inside of hollowed-out
components. Maybe you can stash a modern ceramic inside of the
paper/wax tube, and seal it up with a bit of hot glue...

Ceramic capacitors are mostly cheap crap. Some have a wide change in
capacitance, at different voltages. Some are microphonic, and their
normal failure mode is a dead short. About the only place they should be
used are for DC bybass, or in low power tuned circuits.


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Dave Platt]

That word "film" bothers me, anyhow. Just what the heck is this film? Is
it just some sprayed on metalic particles? The old paper caps contained
foil, which to me means something that looks like tin foil used in the
kitchen. Maybe I'm wrong, but if my radio or (whatever) was designed for
caps made with foil, I'd prefer to use caps with foil, and whatever
plastics they used to replace the paper. In other words, I want caps
that most closely mimic the original caps, except without the paper.

Then, what you are looking for would be what's sold as "film and foil"
capacitors.

Digi-Key sells e.g. the CDE "WMF" series, which use metal foil, a
polyester dielectric film, "non-inductive" winding (which usually
means that the foil sticks out past the end of the film, and the turns
of the foil are bonded directly to the wire lead), and epoxy seals at
either end. These, or similar, might be the closest thing to a
"plastic drop-in replacement" for your old paper-and-foil caps.

The film-and-foil design is often preferred for applications where
there's a high peak current (e.g. pulse applications) as the current
carrying capability of the foil is considerable.

The other (more common) option is "metallized film". In this design,
the dielectric film (polyester, polypropylene, etc.) has a thin
conductive metal layer deposited on one side - typically via vaccum
deposition I believe. It's not discrete particles of any real size.
Two layers of this film are then spiral-wound together, with the wire
leads being bonded to the leads at the ends.

Metallized-film (sometimes "stacked film") tend to be less expensive,
and (I think) more capacity available per volume at any give voltage
rating because the conductive layer is so thin.

They are also said to have a reliability advantage, at least
potentially. If a pinhole develops in the film and two adjacent
layers short together, the short-circuit current can burn away the
conductive film right around the hole, "healing" the short.
Apparently this only works well when the film is a material with a
high oxygen content.

http://www.ecicaps.com/tech-tools/technical-papers/self-healing-affect-metallized-capacitors/

 

On Wednesday, 9 August 2017 19:50:17 UTC+1, Michael Terrell wrote:

Ceramic capacitors are mostly cheap crap. Some have a wide change in
capacitance, at different voltages. Some are microphonic, and their
normal failure mode is a dead short. About the only place they should be
used are for DC bybass, or in low power tuned circuits.

Hmmm. I've not found them crap. Excluding MLCCs, which are a different animal to the rest, ceramics are immune to the melting problems of some plastic film caps, their light weight aids robustness, they're small, they typically handle way above rated voltage without trouble if ever necessary. Slight microphony is not a problem in lots of applications - it is only very slight. The C/V gotcha only applies to some, and obviously one need be aware of it at design time and choose accordingly.

All parts have their issues, and ceramics behave fine and are very reliable in a lot of situations. As with everything, not in every situation.


NT