Why should someone replace ALL the capacitors on old Tube eq

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

I understand that the electrolytic caps contain chemicals which decay
over time, from the chemicals corroding the metal parts. So,
electrolytic caps should always be replaced. But why replace the old
paper caps coated with wax? All they are, is metal foil and paper rolled
up, and as long as the wax is sealing them to keep out moisture, why
should they become defective?

And for that matter, what are the new ones made from? Aside from being
sealed inside of some sort of plastic (instead of wax), are they not the
exact same thing inside?

While this is not part of my original intent for this message, I want to
ask if anyone remembers the old oil filled electrolytic caps in the
1930's and 40's radios? I never understood what the oil did inside of
them. But what I do remember is having one of them "blow". *SCARY SHIT*.
I plugged in some ancient chassis with those old oil filled caps, and
all of a sudden there was hot oil spraying all over me, from the tiny
hole in the top of it. After that, I always put a tin can over those
caps before plugging the device in. (or just replaced them). Those
seemed to almost always be bad. (Probably why they were not used to too
many years).

 

On Thursday, February 2, 2017 at 3:57:12 PM UTC-5, olds...@tubes.com wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

I understand that the electrolytic caps contain chemicals which decay
over time, from the chemicals corroding the metal parts. So,
electrolytic caps should always be replaced. But why replace the old
paper caps coated with wax? All they are, is metal foil and paper rolled
up, and as long as the wax is sealing them to keep out moisture, why
should they become defective?

And for that matter, what are the new ones made from? Aside from being
sealed inside of some sort of plastic (instead of wax), are they not the
exact same thing inside?

While this is not part of my original intent for this message, I want to
ask if anyone remembers the old oil filled electrolytic caps in the
1930's and 40's radios? I never understood what the oil did inside of
them. But what I do remember is having one of them "blow". *SCARY SHIT*.
I plugged in some ancient chassis with those old oil filled caps, and
all of a sudden there was hot oil spraying all over me, from the tiny
hole in the top of it. After that, I always put a tin can over those
caps before plugging the device in. (or just replaced them). Those
seemed to almost always be bad. (Probably why they were not used to too
many years).

If you remove every paper and foil capacitor from an old tube anything and check them on a quality checker, you'll find most if not all showing some sort of defect. They may read OK value wise, but run a few hundred volts through them and you'll find most have a lot of internal leakage. The fact is that moisture does eventually penetrate the capacitors and causes problems.

I've heard that old Radiolas use large banks of paper and foil capacitors instead of electrolytics and most do just fine with their original caps. Supposedly it's because of the particularly fine rice paper imported from Japan used to construct these capacitors during the 1920s. These rice paper caps might escape degradation over the decades. Perhaps those who've restored a bunch of these can comment if they actually did dynamic testing of the capacitors.

 

[Foxs Mercantile]

On 2/2/2017 2:53 PM, oldschool@tubes.com wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

Most "old" radios are from 1930-1960.
That makes them 87-57 years old.

Manufacturing has changed a lot.

I change all the caps simply because I don't waste my time
"troubleshooting" bad caps.
Bad caps can cause collateral damage.
Why risk it for the cost (low) of replacement parts?

Old electrolytic filter caps dry out.
It's a fools game to waste time trying to reform them.
Paper dielectric capacitor absorb moisture and that
combines with the acids in the paper and cause them to fail.

For the most part, mica, silver dipped mica and ceramic
capacitors are very reliable. The band ones, you can find
AFTER you've replaced the usual suspects and can actually
trouble shoot the radio rather than running around in circles
chasing known bad parts.

Yes, I've had to replace the occasional vacuum tube, or found
an open coil, but for the most part 99% of the radios I've
worked on, worked to a fashion by just replacing known bad
parts. I.e. Paper and electrolytic capacitors.



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

 

On Thu, 2 Feb 2017 15:38:45 -0600, Foxs Mercantile <jdangus@att.net>
wrote:

On 2/2/2017 2:53 PM, oldschool@tubes.com wrote:
Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

Most "old" radios are from 1930-1960.
That makes them 87-57 years old.

Manufacturing has changed a lot.

I change all the caps simply because I don't waste my time
"troubleshooting" bad caps.
Bad caps can cause collateral damage.
Why risk it for the cost (low) of replacement parts?

Old electrolytic filter caps dry out.
It's a fools game to waste time trying to reform them.
Paper dielectric capacitor absorb moisture and that
combines with the acids in the paper and cause them to fail.

For the most part, mica, silver dipped mica and ceramic
capacitors are very reliable. The band ones, you can find
AFTER you've replaced the usual suspects and can actually
trouble shoot the radio rather than running around in circles
chasing known bad parts.

Yes, I've had to replace the occasional vacuum tube, or found
an open coil, but for the most part 99% of the radios I've
worked on, worked to a fashion by just replacing known bad
parts. I.e. Paper and electrolytic capacitors.

I'm 66 years old. According to my doctor, I dont have any bad
capacitors, (just arthritis).

Seriously, I wonder what the life expectancy is for the new caps
(meaning the replacements for the wax coated paper caps. ???)

And what are these newer ones made from?

I know the mica and ceramic caps are reliable and last almost forever.

A for electrolytic caps, it seems that the newer ones have a much
shorter life than the old ones did. You'd think that it would be the
other way around with modern technology, but today the name of the game
to to make stuff as cheaply as possible, for profit, not long life.
After all, today's electronics, cars, even homes are disposible. That's
why those old radios still work after 60 or 80 years, while most stuff
made today is in a landfill in less than 10 years.

One other thing that most people dont know, is that if we have a nuclear
blast, all of the semiconductors will cease to work. That means all
modern electronics, radios, tvs, cpmputers, cars, and darn near
everything around us, will stop working. The only stuff that will still
work are tube based electronics and vehicles made which still have
ignition points in their distributors.

Most likely WE wont survive either, but if we do, all we will have is
the old stuff from the 1960s and earlier, to rely on. The internet will
be gone, since it's all run with silicon. Most radio transmissions will
also be gone, except those still powered with tubes. This day is coming
soon, and we will be tossed back into the early 1900s. Thats why we need
to keep this old technology alive. The gear we relied on during WW2 is
the gear we will rely on once again during the upcoming WW3.

 

[Jim Mueller]

On Thu, 02 Feb 2017 14:53:42 -0600, oldschool wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

I understand that the electrolytic caps contain chemicals which decay
over time, from the chemicals corroding the metal parts. So,
electrolytic caps should always be replaced. But why replace the old
paper caps coated with wax? All they are, is metal foil and paper rolled
up, and as long as the wax is sealing them to keep out moisture, why
should they become defective?

And for that matter, what are the new ones made from? Aside from being
sealed inside of some sort of plastic (instead of wax), are they not the
exact same thing inside?

While this is not part of my original intent for this message, I want to
ask if anyone remembers the old oil filled electrolytic caps in the
1930's and 40's radios? I never understood what the oil did inside of
them. But what I do remember is having one of them "blow". *SCARY SHIT*.
I plugged in some ancient chassis with those old oil filled caps, and
all of a sudden there was hot oil spraying all over me, from the tiny
hole in the top of it. After that, I always put a tin can over those
caps before plugging the device in. (or just replaced them). Those
seemed to almost always be bad. (Probably why they were not used to too
many years).

Actually, the electrolytic capacitors are more likely to be good than the
paper capacitors. Almost all of the paper capacitors I have from the
"old days" are bad, even if they were never used while a small number of
the electrolytics are still functional.

The paper capacitors were made of sheets of foil separated by paper,
"sealed" in wax. Unfortunately, wax isn't a very good seal; moisture can
penetrate it. These capacitors were a know failure point 10 years after
a set was made. There just wasn't anything better to replace them with
(at a reasonable price). Modern capacitors are made from plastic film
that is much less affected by moisture and is a better insulator in the
first place.

The old electrolytic capacitors you are talking about don't sound like
the oil filled variety. Indeed, if they are electrolytic, they aren't
oil filled. Oil filled capacitors aren't polarized and many of them are
good today. They were the high quality capacitors used in military and
premium industrial equipment; you seldom find them in consumer gear
unless someone has repaired it with surplus parts. The capacitors you
talk about are more likely wet electrolytics. They aren't filled with
oil but with an acid. They are indeed all bad; don't power a set that
has them. Sometimes they leak if you turn them upside down (the vent
hole you mentioned). And be careful not to puncture them while you are
removing them. If there is still any acid inside, it will corrode any
metal it gets on.

You can still get high quality electrolytic capacitors from authorized
distributors like Mouser or Digi-Key. No-name ones from Amazon or Ebay
are likely to be junk. Name brand ones from these latter sources may be
counterfeit.

While tube electronics may survive a nuclear war, it is irrelevant.
There won't be any electricity to run them. The power plants are
controlled by computers. Likewise, having your own generator won't help
either. Many of the new ones are also semiconductor based, and you won't
be able to get gas to run them since the pumps at the gas station are run
by electricity which won't be available. Solar cells are also
semiconductors and the inverters used with them also use semiconductors.
So, if there is a WW3, don't count on ANYTHING electrical working.

--
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.

 

[Jeff Liebermann]

On Thu, 02 Feb 2017 16:44:53 -0600, oldschool@tubes.com wrote:

I'm 66 years old. According to my doctor, I dont have any bad
capacitors, (just arthritis).

I'm 69 years old. My body mechanic says I have pump and inside
plumbing problems. Perhaps I should replace him with a plumber?

Seriously, I wonder what the life expectancy is for the new caps
(meaning the replacements for the wax coated paper caps. ???)

There are online lifetime calculators for electrolytic and other types
of capacitors. For example:
<http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx>
<http://www.chemi-con.com/education> (click on Capacitor Life)
The major culprit is internal heating from high ripple current
resulting the electrolyte leaking or evaporating. Temperature also
has a big effect. There are graphs on the capacitor data sheets that
approximate the lifetime characteristics.

>And what are these newer ones made from?

For electrolytics, try polymer caps:
<https://en.wikipedia.org/wiki/Polymer_capacitor#Lifetime.2C_service_life>
<http://www.mouser.com/pdfdocs/Panasonic_Capacitors_WP_final.PDF>

>I know the mica and ceramic caps are reliable and last almost forever.

Not all ceramics are that reliable. MLCC (multi-layer ceramic caps)
are rather fragile and microphonic.

A for electrolytic caps, it seems that the newer ones have a much
shorter life than the old ones did.

Nope. The old ones filtered at 120 Hz. The new caps filter at 100 to
300 KHz. Internal dissipation follows frequency.

That's
why those old radios still work after 60 or 80 years, while most stuff
made today is in a landfill in less than 10 years.

Todays products are intentionally designed to be difficult to repair
and to only last as long as the warranty period. With the proper
design tools and models, it is possible to predict the life of an
electronic (or mechanical) product. Anything that lasts longer than
the warranty period is deemed to be "over-designed". It is then
redesigned using lower rating or cost components so that everything
blows up at the same time. I've seen it happen.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

[pfjw@aol.com]

On Thursday, February 2, 2017 at 4:33:51 PM UTC-5, ohg...@gmail.com wrote:

Perhaps those who've restored a bunch of these can comment if they actually did dynamic testing of the capacitors.

I have done a fair number of AK55s and their Radiola and other-brand contemporaries, using potted 1 & 2 uF paper caps. I will typically test them at 500VAC on a proper full-voltage cap tester.

I have never, repeat, never found a bad potted paper cap in an undamaged device. The secret, in my opinion, is that the caps are massive (I have unpotted a couple for the sake of curiosity from rusted-out hulks), with wide clearances. The potting tar makes for an excellent seal as well.

Peter Wieck
Melrose Park, PA

 

[Adrian Tuddenham]

<oldschool@tubes.com> wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

One of the factors that is often overlooked is the tolerance of the
circuit to the various types of wear-out mechanism.

If a cathode by-pass capacitor on the sound output valve goes leaky, it
would have to leak very badly indeed (and measure only a few hundred
ohms) before it upset the operating conditions of the valve. On the
other hand, if an inter-stage coupling capacitor begin to leak and puts
even a small proportion of the anode voltage of the first valve across
the grid leak of the second, it will upset the second valve very badly
and may even destroy it.

Electrolytic smoothing capacitors in the HT line will leak even when
brand new, but the leakage is usually fairly small once they have
settled down. If they later begin to leak badly, this will cause
internal heating and damage which may not be obvious - the set will
appear to carry on working as normal. Eventually, when the leakage
increases even more, something in the power supply will fail due to
overloading or the capacitor itself bursts; but until that point, there
may be no hint that things are going wrong because the circuit is
reasonably tolerant of that sort of leakage.

I have repaired QuadII amplifiers which almost met specification even
though the internal voltages were all over the place, most of the
capacitors were leaking and some of the resistors had changed value too.
The initial design was intended to be tolerant of a wide range of
component values (close-tolerance components were very expensive) so it
wasn't badly upset by drift due to ageing.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[Phil Hobbs]

On 02/02/2017 09:36 PM, Jeff Liebermann wrote:

On Thu, 02 Feb 2017 16:44:53 -0600, oldschool@tubes.com wrote:

I'm 66 years old. According to my doctor, I dont have any bad
capacitors, (just arthritis).

I'm 69 years old. My body mechanic says I have pump and inside
plumbing problems. Perhaps I should replace him with a plumber?

Seriously, I wonder what the life expectancy is for the new caps
(meaning the replacements for the wax coated paper caps. ???)

There are online lifetime calculators for electrolytic and other types
of capacitors. For example:
http://www.illinoiscapacitor.com/tech-center/life-calculators.aspx
http://www.chemi-con.com/education> (click on Capacitor Life)
The major culprit is internal heating from high ripple current
resulting the electrolyte leaking or evaporating. Temperature also
has a big effect. There are graphs on the capacitor data sheets that
approximate the lifetime characteristics.

And what are these newer ones made from?

For electrolytics, try polymer caps:
https://en.wikipedia.org/wiki/Polymer_capacitor#Lifetime.2C_service_life
http://www.mouser.com/pdfdocs/Panasonic_Capacitors_WP_final.PDF

I know the mica and ceramic caps are reliable and last almost forever.

Not all ceramics are that reliable. MLCC (multi-layer ceramic caps)
are rather fragile and microphonic.

A for electrolytic caps, it seems that the newer ones have a much
shorter life than the old ones did.

Nope. The old ones filtered at 120 Hz. The new caps filter at 100 to
300 KHz. Internal dissipation follows frequency.

That's
why those old radios still work after 60 or 80 years, while most stuff
made today is in a landfill in less than 10 years.

Todays products are intentionally designed to be difficult to repair
and to only last as long as the warranty period. With the proper
design tools and models, it is possible to predict the life of an
electronic (or mechanical) product. Anything that lasts longer than
the warranty period is deemed to be "over-designed". It is then
redesigned using lower rating or cost components so that everything
blows up at the same time. I've seen it happen.

Oliver Wendell Holmes wrote a very funny poem about that, "The Deacon's
Masterpiece, Or, The Wonderful One-Hoss Shay".

Here it is, read by Eddie Albert.

https://www.youtube.com/watch?v=wiOHhhwnK6k

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

On Friday, February 3, 2017 at 2:08:40 PM UTC-5, Nick Danger wrote:

On 2/2/2017 9:13 PM, Jim Mueller wrote:


Seeing as you brought up WW3, for those of you that may not know it, a
new president singlehandedly advanced the Doomsday Clock by 30 seconds
just last week. Heck of a job!

You probably don't know this, but it's not a *real clock*. It's one of those cardboard affairs that we used to teach our children how to tell time. Some snowflakes have one that they labelled "Doomsday" on it in crayon and they move the hands one way or the other depending on how *they* feel about things.

If there were no Muslims and Communists, this would be a pretty peaceful world actually. And speaking of Communists, it was lovely of the outgoing U.S. president to throw the cold war back decades before he left.

That's a heck of a job!

 

[pfjw@aol.com]

Lemme See:

Austria in 1936.
Chamberlain: Peace in our Time.

And we all know how that turned out.

Crimea in 2016.
Ukraine in 2017? It is a shooting war to this day, and Ukraine is losing.
tRump: Peace in our time, and let's go to bed.

Expect any different? Only this time with Nukes.

On some great and glorious day the plain folks of the land will reach their heart's desire at last, and the White House will be adorned by a downright moron.

In this world of sin and sorrow there is always something to be thankful for; as for me, I rejoice that I am not a Republican.

H. L. Mencken

Peter Wieck
Melrose Park, PA

 

[Tom Biasi]

On 2/3/2017 10:12 AM, Phil Hobbs wrote:

On 02/02/2017 09:36 PM, Jeff Liebermann wrote:
On Thu, 02 Feb 2017 16:44:53 -0600, oldschool@tubes.com wrote:
....


Oliver Wendell Holmes wrote a very funny poem about that, "The Deacon's
Masterpiece, Or, The Wonderful One-Hoss Shay".

Here it is, read by Eddie Albert.

https://www.youtube.com/watch?v=wiOHhhwnK6k

Cheers

Phil Hobbs

A wonderful poem and read very well.

 

[Jeff Liebermann]

On Fri, 3 Feb 2017 10:12:56 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 02/02/2017 09:36 PM, Jeff Liebermann wrote:
Todays products are intentionally designed to be difficult to repair
and to only last as long as the warranty period. With the proper
design tools and models, it is possible to predict the life of an
electronic (or mechanical) product. Anything that lasts longer than
the warranty period is deemed to be "over-designed". It is then
redesigned using lower rating or cost components so that everything
blows up at the same time. I've seen it happen.

Oliver Wendell Holmes wrote a very funny poem about that, "The Deacon's
Masterpiece, Or, The Wonderful One-Hoss Shay".
Here it is, read by Eddie Albert.
https://www.youtube.com/watch?v=wiOHhhwnK6k
Cheers
Phil Hobbs

Thanks, that was good and quite appropriate.

While attending college, I lived for a time in a large old house aptly
named "the fire trap". I could hear termites chewing away in the
walls. About 3 years after graduating, I returned to visit the
school, and drove by house. It looked much the same as when I lived
there. The next day, on my way out of town, I drove by again and
found that the house had collapsed in a heap. No wall was left
standing. According to the news, it had fallen down by itself and
without warning, injuring a few students in the process. It's much
like the medieval cathedrals, bridges, and other structures, where the
failure of one tiny arch, will cause the entire structure to collapse.


In a previous life, I tried to design a "warranty timer" into a
product. Actually, it was suppose to accumulate and display the
amount of time that the unit had been powered on to help establish
maintenance intervals. In previous products, a mechanical
counter-timer was used, but for this version, it was deemed too big
and expensive.
<http://www.alliedelec.com/images/products/Small/70132720.jpg>
I found a company that made an electrochemical equivalent. It was
housed in a glass cylinder, similar to a common 3AG glass fuse. Inside
was some chemical solution. When a few volts of DC was applied,
electrolytic action caused one end to slowly turn dark, thus
indicating the amount of time that the DC was applied. Sorry, but I
couldn't find the vendor or an equivalent online. When the required
maintenance was performed, the indicator would be replaced as it could
not be reset.

During the design phase, I liked to joke about installing a 2nd timer
in the product, which would blow it up after a specified operating
life. I even designed a place for it on one of PCB's. I stopped
joking after I found that management was taking me seriously and
discussing such things was how to handle extended warranties. The
device was later removed in a cost reduction exercise, but the
component outline remained in the printed manual, resulting in
numerous embarrassing questions because someone had labeled the part
as a "warranty timer".




--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

 

On Fri, 03 Feb 2017 09:32:07 -0800, Jeff Liebermann <jeffl@cruzio.com>
wrote:

On Fri, 3 Feb 2017 10:12:56 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

On 02/02/2017 09:36 PM, Jeff Liebermann wrote:
Todays products are intentionally designed to be difficult to repair
and to only last as long as the warranty period. With the proper
design tools and models, it is possible to predict the life of an
electronic (or mechanical) product. Anything that lasts longer than
the warranty period is deemed to be "over-designed". It is then
redesigned using lower rating or cost components so that everything
blows up at the same time. I've seen it happen.

Oliver Wendell Holmes wrote a very funny poem about that, "The Deacon's
Masterpiece, Or, The Wonderful One-Hoss Shay".
Here it is, read by Eddie Albert.
https://www.youtube.com/watch?v=wiOHhhwnK6k
Cheers
Phil Hobbs

Thanks, that was good and quite appropriate.

While attending college, I lived for a time in a large old house aptly
named "the fire trap". I could hear termites chewing away in the
walls. About 3 years after graduating, I returned to visit the
school, and drove by house. It looked much the same as when I lived
there. The next day, on my way out of town, I drove by again and
found that the house had collapsed in a heap. No wall was left
standing. According to the news, it had fallen down by itself and
without warning, injuring a few students in the process. It's much
like the medieval cathedrals, bridges, and other structures, where the
failure of one tiny arch, will cause the entire structure to collapse.


In a previous life, I tried to design a "warranty timer" into a
product. Actually, it was suppose to accumulate and display the
amount of time that the unit had been powered on to help establish
maintenance intervals. In previous products, a mechanical
counter-timer was used, but for this version, it was deemed too big
and expensive.
http://www.alliedelec.com/images/products/Small/70132720.jpg
I found a company that made an electrochemical equivalent. It was
housed in a glass cylinder, similar to a common 3AG glass fuse. Inside
was some chemical solution. When a few volts of DC was applied,
electrolytic action caused one end to slowly turn dark, thus
indicating the amount of time that the DC was applied. Sorry, but I
couldn't find the vendor or an equivalent online. When the required
maintenance was performed, the indicator would be replaced as it could
not be reset.

During the design phase, I liked to joke about installing a 2nd timer
in the product, which would blow it up after a specified operating
life. I even designed a place for it on one of PCB's. I stopped
joking after I found that management was taking me seriously and
discussing such things was how to handle extended warranties. The
device was later removed in a cost reduction exercise, but the
component outline remained in the printed manual, resulting in
numerous embarrassing questions because someone had labeled the part
as a "warranty timer".
Something like a coulometer???

 

[Nick Danger]

On 2/2/2017 9:13 PM, Jim Mueller wrote:

While tube electronics may survive a nuclear war, it is irrelevant.
There won't be any electricity to run them. The power plants are
controlled by computers. Likewise, having your own generator won't help
either. Many of the new ones are also semiconductor based, and you won't
be able to get gas to run them since the pumps at the gas station are run
by electricity which won't be available. Solar cells are also
semiconductors and the inverters used with them also use semiconductors.
So, if there is a WW3, don't count on ANYTHING electrical working.

Seeing as you brought up WW3, for those of you that may not know it, a
new president singlehandedly advanced the Doomsday Clock by 30 seconds
just last week. Heck of a job!

 

[Jim Mueller]

On Fri, 03 Feb 2017 13:50:22 +0000, Adrian Tuddenham wrote:

oldschool@tubes.com> wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

One of the factors that is often overlooked is the tolerance of the
circuit to the various types of wear-out mechanism.

snip

True. But the reason to replace them ALL is that if you only replace the
one(s) causing a problem, another will fail later, then another still
later. It is much easier to do them all at once than to have to repair
the same unit over and over as they fail one after another. Been there,
done that.

--
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.

 

[Benderthe.evilrobot]

<oldschool@tubes.com> wrote in message
news:32779ctsu0qa604ak706qamu4fft571fj8@4ax.com...

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

I understand that the electrolytic caps contain chemicals which decay
over time, from the chemicals corroding the metal parts. So,
electrolytic caps should always be replaced. But why replace the old
paper caps coated with wax? All they are, is metal foil and paper rolled
up, and as long as the wax is sealing them to keep out moisture, why
should they become defective?

Waxed paper capacitors are notorious for moisture absorbtion and becoming
leaky.

There are plenty of other types of dry capacitors that don't last forever in
the high temperature around tubes.

 

[Benderthe.evilrobot]

<oldschool@tubes.com> wrote in message
news:nua79chv7ato1hdgir79d0ku56j3s3upnt@4ax.com...

On Thu, 2 Feb 2017 15:38:45 -0600, Foxs Mercantile <jdangus@att.net
wrote:

On 2/2/2017 2:53 PM, oldschool@tubes.com wrote:
Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

Most "old" radios are from 1930-1960.
That makes them 87-57 years old.

Manufacturing has changed a lot.

I change all the caps simply because I don't waste my time
"troubleshooting" bad caps.
Bad caps can cause collateral damage.
Why risk it for the cost (low) of replacement parts?

Old electrolytic filter caps dry out.
It's a fools game to waste time trying to reform them.
Paper dielectric capacitor absorb moisture and that
combines with the acids in the paper and cause them to fail.

For the most part, mica, silver dipped mica and ceramic
capacitors are very reliable. The band ones, you can find
AFTER you've replaced the usual suspects and can actually
trouble shoot the radio rather than running around in circles
chasing known bad parts.

Yes, I've had to replace the occasional vacuum tube, or found
an open coil, but for the most part 99% of the radios I've
worked on, worked to a fashion by just replacing known bad
parts. I.e. Paper and electrolytic capacitors.

I'm 66 years old. According to my doctor, I dont have any bad
capacitors, (just arthritis).

Seriously, I wonder what the life expectancy is for the new caps
(meaning the replacements for the wax coated paper caps. ???)

And what are these newer ones made from?

I know the mica and ceramic caps are reliable and last almost forever.

I've seen loads of ceramic caps fail - but mostly in TV horizontal scan
sections where the frequency is over 15kHz and high voltage pulse
conditions.

This got worse with ever increasing PC monitor resolutions.

AFAICR; mica caps were pretty reliable - in most of the places I found them,
they were used for precision and a specific tempco.

 

[Tom Biasi]

On 2/3/2017 2:08 PM, Nick Danger wrote:

On 2/2/2017 9:13 PM, Jim Mueller wrote:

While tube electronics may survive a nuclear war, it is irrelevant.
There won't be any electricity to run them. The power plants are
controlled by computers. Likewise, having your own generator won't help
either. Many of the new ones are also semiconductor based, and you won't
be able to get gas to run them since the pumps at the gas station are run
by electricity which won't be available. Solar cells are also
semiconductors and the inverters used with them also use semiconductors.
So, if there is a WW3, don't count on ANYTHING electrical working.


Seeing as you brought up WW3, for those of you that may not know it, a
new president singlehandedly advanced the Doomsday Clock by 30 seconds
just last week. Heck of a job!


Get off of it. You lost.

 

[Ralph Mowery]

In article <5894f007$0$55577$b1db1813$7968482@news.astraweb.com>,
wrongname@nospam.com says...

On Fri, 03 Feb 2017 13:50:22 +0000, Adrian Tuddenham wrote:

oldschool@tubes.com> wrote:

Why should someone replace ALL the capacitors on old Tube equipment?

It seems that some people advocate that.

One of the factors that is often overlooked is the tolerance of the
circuit to the various types of wear-out mechanism.

snip

True. But the reason to replace them ALL is that if you only replace the
one(s) causing a problem, another will fail later, then another still
later. It is much easier to do them all at once than to have to repair
the same unit over and over as they fail one after another. Been there,
done that.

I believe in replacing most all the components that are similar when one
fails in older equipment. I worked at a large plant and when a 200 HP
motor speed control went bad a factory man was called in. He found two
power diodes bad. As this was a 3 phase motor and had one more, I asked
him to replace it. He told me they were about $ 100 each. I said go
ahead. The down time was costing us much more than that an hour,and to
get him back in would cost a lot more if the 3 rd one failed, it would
be just good insurance. The diode may or may not have been weakened in
some way. $ 100 is a small part of over $ 50,000 or more.