When I started getting into the wonderful world of tube amps, I also heard
of these beasts - oil caps. Of course you all know what I am talking about,
but my question is what are they? I know what a capacitor is, but why oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

Oil caps are standard film (perhaps polyethylene) and foil (aluminum)
spiral-wound caps, the difference (and name) is in the whole deal being
submerged and impregnated with a dielectric oil.
Often comes in a metal can, commonly used for motors which require a
run capacitor. (Start caps are usually cheap bipolar electrolytics;
they can be lossy like that because they only start the motor.)

Although for special purposes (very high peak currents, perhaps an
induction furnace supply) I suppose you could use a welded stack of
plates and free flowing oil between them to provide cooling.

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

"ComoEstasAmigo" wrote in message
...
When I started getting into the wonderful world of tube amps, I also heard
of these beasts - oil caps. Of course you all know what I am talking
about,
but my question is what are they? I know what a capacitor is, but why oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

Hi RATs!

I use oil caps in my power supply because they sound better than anything else
I have tried

Why they sound better is of no interest to me.

Why do I like kissing my wife? Who cares?

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

TubeGarden wrote:

Hi RATs!

I use oil caps in my power supply because they sound better than anything else
I have tried

Why they sound better is of no interest to me.

Why do I like kissing my wife? Who cares?

Happy Ears!
Al

Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Oil filled caps are also used to correct Power Factor in power distribution
systems. Bet that sounds better too, but I sure can't hear the result!!!!!!!
Cheers, John Stewart

If you can't measure it, It may not be. JLS

ComoEstasAmigo wrote:

When I started getting into the wonderful world of tube amps, I also heard
of these beasts - oil caps. Of course you all know what I am talking about,
but my question is what are they? I know what a capacitor is, but why oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

The earlier caps used metal foils rolled up with waxed paper
between the "plates"
These failed regularly, after the paper decomposed,
or absorbed moisture.
Oil is a good insulator, and instead of wax,
oils were used between the plates to soak the paper.
I have had to remove lots of these when the seals broke down,
and oil leaked out all over the chassis.
Some oil caps are better than others due to the rugged construction.

I don't like oil caps anywhere in audio amps, prefering
polypropylene types for coupling, and electrolytic for
power supply rails, sometimes also bypassed with poly types to extend
the bandwidth of the cap.

Some caps using oil had quite toxic types of oil, and one can't always
know what oil is used. I have a box of oil caps between 1uF and 10 uF,
all with typical 1 kV+ ratings, all are far too low a value for
my audio amps.
Do oil caps sound better? I doubt it.
Do teflon caps sound better? I don't know.

Patrick Turner.

Patrick Turner wrote:

ComoEstasAmigo wrote:

When I started getting into the wonderful world of tube amps, I also heard
of these beasts - oil caps. Of course you all know what I am talking about,
but my question is what are they? I know what a capacitor is, but why oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

The earlier caps used metal foils rolled up with waxed paper
between the "plates"
These failed regularly, after the paper decomposed,
or absorbed moisture.
Oil is a good insulator, and instead of wax,
oils were used between the plates to soak the paper.
I have had to remove lots of these when the seals broke down,
and oil leaked out all over the chassis.
Some oil caps are better than others due to the rugged construction.

I don't like oil caps anywhere in audio amps, prefering
polypropylene types for coupling, and electrolytic for
power supply rails, sometimes also bypassed with poly types to extend
the bandwidth of the cap.

Some caps using oil had quite toxic types of oil, and one can't always
know what oil is used. I have a box of oil caps between 1uF and 10 uF,
all with typical 1 kV+ ratings, all are far too low a value for
my audio amps.
Do oil caps sound better? I doubt it.
Do teflon caps sound better? I don't know.

Patrick Turner.

The reason you can get the 'old sound' with paper-in-oil caps is just
that they are so small and you get a lovely saggy B+ rail, with its
particular type of compression. For hi-fi, bad, but for guitar, indispensable.
You don't of course need paper-in-oil, but you do need little caps - 8uF + 8uF
is typical for 2 x 6V6 or even 2 x 6L6. Bigger is not always better.

best

Andy Cowley

the "oil" was sometimes a "polychlorinated biphenyl" -- great for insulation
and cooling, not so great for things like chloracne.

"Patrick Turner" wrote in message
...


ComoEstasAmigo wrote:

When I started getting into the wonderful world of tube amps, I also
heard
of these beasts - oil caps. Of course you all know what I am talking
about,
but my question is what are they? I know what a capacitor is, but why
oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

The earlier caps used metal foils rolled up with waxed paper
between the "plates"
These failed regularly, after the paper decomposed,
or absorbed moisture.
Oil is a good insulator, and instead of wax,
oils were used between the plates to soak the paper.
I have had to remove lots of these when the seals broke down,
and oil leaked out all over the chassis.
Some oil caps are better than others due to the rugged construction.

I don't like oil caps anywhere in audio amps, prefering
polypropylene types for coupling, and electrolytic for
power supply rails, sometimes also bypassed with poly types to extend
the bandwidth of the cap.

Some caps using oil had quite toxic types of oil, and one can't always
know what oil is used. I have a box of oil caps between 1uF and 10 uF,
all with typical 1 kV+ ratings, all are far too low a value for
my audio amps.
Do oil caps sound better? I doubt it.
Do teflon caps sound better? I don't know.

Patrick Turner.

Do oil caps sound better? I doubt it.
Do teflon caps sound better? I don't know.

Hi RATs!

Knowledge and doubt are not factors in my opinion of how my amp sounds. If I
like it, it is all I need to keep it that way

I guess it would be easier if everyone heard the same and could agree on
absolute sonic parameters, but, really, pretty dull, too

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Do oil cap sound better? NOT
Do oil caps make sound? YES, when they blow.
( happens when they are overloaded )
Are they big for the uF value given? YES
Do they last a long time? YES sometimes longer than the owner.
Oil caps have their place, not in amps.



"TubeGarden" wrote in message
...
Do oil caps sound better? I doubt it.
Do teflon caps sound better? I don't know.

Hi RATs!

Knowledge and doubt are not factors in my opinion of how my amp sounds. If
I
like it, it is all I need to keep it that way

I guess it would be easier if everyone heard the same and could agree on
absolute sonic parameters, but, really, pretty dull, too

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

CBM wrote:

Do oil cap sound better? NOT
Do oil caps make sound? YES, when they blow.
( happens when they are overloaded )
Are they big for the uF value given? YES
Do they last a long time? YES sometimes longer than the owner.
Oil caps have their place, not in amps.

Oil caps are good in gtr amps, bad in hifi. Only
good because they are small (uF) though.

Andy Cowley

"ComoEstasAmigo" wrote

When I started getting into the wonderful world of tube amps, I
also heard
of these beasts - oil caps. Of course you all know what I am
talking about,
but my question is what are they? I know what a capacitor is, but
why oil?
What oil? What does this "oil" do that normal vaccum or air
between the
plates does not do? Thanks

Vacuum or air is not normal for audio amplifiers. They would be too
big and heavy. Solid dielectrics are used because they hold thin
plates apart at a reliable short distance. If you could think of a
cheap way of doing that with a vacuum you could make a fortune.

The quality of a capacitor is partly in its construction, and partly
in the materials used for the plates and the dielectric. Most
well-made plastic caps produce close to zero distortion in most
circumstances.

By oil, I assume you mean paper and oil. These produce measurable
amounts of distortion, mostly 2H but also some 3H and a little IMD,
especially with high bias voltages and/or high signal voltages.
Measurable is not necessarily audible...perhaps -80dB or less.

Polar electrolytics are often considerably worse, with more
high-order harmonics and IMD, but vary a lot depending on value and
manufacture.

Perhaps judicious use of paper-in-oil could help cancel 2H produced
elsewhere, who knows? Perhaps really well-made ones are better than
the ones in the test I read. Many people believe in them.

Anything other than a vacuum in a changing electric field will
wriggle a bit inside somehow. Wriggles can be linear or non-linear,
elastic or damped, and big or small. They store energy and lose some
of it before returning the rest. It is easy to melt PVC, for
example, if you use it as a dielectric.

Is PVC a copolymer? Can't remember. Big subject.

cheers, Ian

Hi RATs!

I like my system. It is neither correct nor perfect. I just like it. You may or
may not agree. You are neither correct nor perfect

You may be young or foolish, but you are not God

He doesn't do email

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

(TubeGarden) said:

Why do I like kissing my wife? Who cares?

*She* does, I suppose? ;-)

--
Sander deWaal
Vacuum Audio Consultancy

"CBM" said:

Do oil cap sound better? NOT
Do oil caps make sound? YES, when they blow.
( happens when they are overloaded )
Are they big for the uF value given? YES
Do they last a long time? YES sometimes longer than the owner.
Oil caps have their place, not in amps.

Uhuh........just replace the oil with Dextron ATF, or, if you're
really looking for the best, with LHM (available at your local Citroen
dealer).

--
Sander deWaal
Vacuum Audio Consultancy

TubeGarden,

What are you on? I am new here, so pardon me for saying this, but your posts
have not contributed to the topic I originally posted one iohta! (there are
some weirdos around this place)

"Ian Iveson" wrote in news:SGIEb.296$i71.760469
@newsfep1-win.server.ntli.net:

snip

Thanks Ian. Very informative.

Hi RATs!

I am on Earth

Sorry you don't enjoy my posts.

Just Killfile me.

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

TubeGarden wrote:

Hi RATs!

I am on Earth

Sorry you don't enjoy my posts.

Just Killfile me.

Happy Ears!
Al

I for one don't need to kilfile you, since you have a garden, where
tubes are grown,
and which flower with blooms of sweet music...

Patrick Turner.



Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"SurfInca" wrote

What are you on? I am new here, so pardon me for saying this, but
your posts
have not contributed to the topic I originally posted one iohta!
(there are
some weirdos around this place)

This seems like a legitimate and valuable contribution to me:

Hi RATs!

I use oil caps in my power supply because they sound better than
anything else
I have tried

Notice that Al only has one power supply. That is because he has
been incrementally, and perhaps occasionally revolutionarily,
matching it to his developing ears and brain for donkeys' years. His
experience is uniquely authoritative. Perhaps unfortunately for the
rest of the world, however, his authority is a unique experience.

Why they sound better is of no interest to me.

IMO Al attributes too much weight to mystery, as if it is the
uniqueness of his experience, rather than the experience itself,
that enlivens his equipment.

OTOH, learning about rapid eye movement blew my trips forever.
Knowledge destroys illusion.

Why do I like kissing my wife? Who cares?

Quite. A biology lesson would be unlikely to improve the experience.

How big a part does illusion play when you listen to music on your
system? This is the key issue. If small, or none, Al could find out
why without threatening his enjoyment. If large, then knowledge
could wreck it.

cheers, Ian

Knowledge destroys illusion.

Why do I like kissing my wife? Who cares?

Quite. A biology lesson would be unlikely to improve the experience.

What wonderful philosophy from Ian.
I really mean that. Sometimes illusions are fantasy which betters
reality,
but then reality is best left to be savoured rather than analysed
simultaneously.

But then the occasional biology lesson would have us managing
kissing times more appropriately, since kissing leads to dancing,
dancing
leads to drinking, drinking leads to eating, eating leads to resting,
and finally to bedtime, when things happen which populate the planet,
put smiles on faces, or cause divorces.
The experience can remain rich and fascinating even though we have
explained it in terms of biology.

Patrick Turner.

Hi RATs!

Yup. Illusion is hard to believe, but, happens, anyway.

I am not against thinking I am just wildly for experiments vs theory

Aural Nirvana may be elusive, but, internal intellectual Nirvana is just not
that much fun, in my booklet.

I started out with the power supply when I built my first 6BM8 SE amp.

I was once a software guy and got to learn first hand, perhaps without my
employer's fullest blessing, how much money is spent reducing the cost of power
supplies.

It is just how business is done

If you want to wiggle the air with authority, you must make the voltage and
current sit very still

It ain't hard, but, it ain't cheap, nor, compact

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

They work great,
Last a long time,
and drain to the bilge.

Bob H.


ComoEstasAmigo wrote:

When I started getting into the wonderful world of tube amps, I also heard
of these beasts - oil caps. Of course you all know what I am talking about,
but my question is what are they? I know what a capacitor is, but why oil?
What oil? What does this "oil" do that normal vaccum or air between the
plates does not do? Thanks

Bob H.

Just grab that plate in one hand, the chassis in the other,
and FEEL the power of tube audio!!!
(not literally, of course, just kidding. DON'T DO THAT!)

Hi Al ,

Yup. Illusion is hard to believe, but, happens, anyway.
I am not against thinking I am just wildly for experiments vs theory

I think the oil cap's have nothing to do with illusion .....
Ever wondered why there's oil in the shockabsorbers of you (nice old) Volvo
?
I think a oil cap works the same so the best place for oil is between the
rect. tube
and the first choke .
Maybe it's time you start thinking a bit Al !! ;-)))))))))))))

Regards ,

Ronald .



Aural Nirvana may be elusive, but, internal intellectual Nirvana is just
not
that much fun, in my booklet.

I started out with the power supply when I built my first 6BM8 SE amp.

I was once a software guy and got to learn first hand, perhaps without my
employer's fullest blessing, how much money is spent reducing the cost of
power
supplies.

It is just how business is done

If you want to wiggle the air with authority, you must make the voltage
and
current sit very still

It ain't hard, but, it ain't cheap, nor, compact

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

Hi RATs!

I think, when I can. I can always Listen

(or, at least, Hear ...)

To tell the truth, I don't know is C1 in my power supply is oil or not It is
0.5uF, 600V in small can, like an oil cap, but I never have had anyone identify
it as an oil cap or not.

It is branded: "Micaflex".

It sounds grand, and sets the plate voltage of the 396A to 150V

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

(TubeGarden) said:

Hi RATs!

I am on Earth

Sorry you don't enjoy my posts.

Just Killfile me.

Happy Ears!
Al

Hey Al!
I always enjoy your posts, which are a breeze of fresh air in an
otherwise hate-filled newsgroup.
Keem 'em coming, puhleeze!


--
Sander deWaal
Vacuum Audio Consultancy

"Ronald" said:

I think the oil cap's have nothing to do with illusion .....
Ever wondered why there's oil in the shockabsorbers of your (nice old) Volvo
?
I think a oil cap works the same so the best place for oil is between the
rect. tube and the first choke .

While I appreciate the use of (paper)oil caps in the power supply and
even as coupling-cap in a tube amp, I fail to see the comparison with
the shock absorbers of a car.
Supply voltage regulation doesn't depend on the *kind* of cap that is
used.
BTW: my nice old Citroens CX and DS benefit greatly of the use of
fresh LHM in their hydraulic systems :-)
BTW2: ever heard of Peter van Willenswaard? He endorses the use of
old, massive oil caps whenever he can.
Read the old issues of Audio & Techniek for that!

--
Sander deWaal
Vacuum Audio Consultancy

Ronald wrote:
Hi Al ,


Yup. Illusion is hard to believe, but, happens, anyway.
I am not against thinking I am just wildly for experiments vs theory


I think the oil cap's have nothing to do with illusion .....
Ever wondered why there's oil in the shockabsorbers of you (nice old) Volvo
?
I think a oil cap works the same so the best place for oil is between the
rect. tube


So, you think that the oil in the cap acts as a viscos damper to motion
of the electrons?

I rather don't think that is likely, given that the electrons of even a
20Hz signal are buzzing back and forth much faster than the fastest
vibration an oil damped shockabsorber will ever react to.

Just because a substance has a certain physical property (viscosity,
lubrication) doesn't mean it will behave that way electrically.

If you want to prove it out, take an oil capacitor, and see how it
behaves electrically, and sonically at 200F, and try it also at 0F.

Capacitor oil is thin as water at 200F, and thick as syrup at
0F. You will find the capacitance changes between these two extremes,
but not really all that much. I don't think you will find that the
audio sounds "really hot" when the cap is at 200F, or has a "shivering"
sound when the cap is at 0F.

-Chuck

Chuck Harris schrieb:

Capacitor oil is thin as water at 200F, and thick as syrup at
0F. You will find the capacitance changes between these two extremes,
but not really all that much. I don't think you will find that the
audio sounds "really hot" when the cap is at 200F, or has a "shivering"
sound when the cap is at 0F.



can you imagine the size of a foil-capacitor of 200F capacity?

the capacity of a paper/oil capacitor is just dependending on the size,
the number of turns and the thickness of the paper between the foil.
The oil is the same as for cooling transformers, some contain
dioxyn, so be careful.
The oil has almost always the same dielectric constant and is
just a simple cooling isolator nothing secret, just vegetable oil...

Peter

I guess I didn't make myself clear enough. By 200F
I meant 200 degrees Farenheit. That's a temperature,
not a capacitance value.

And yes, I can imagine the size of a 200 farad oil-
capacitor. That, among other reasons is why I would
never propose using one in a vacuum tube audio application.

PCB laden oil does not contain dioxin. But it does
decompose to compounds that contain dioxin.

-Chuck

Peter Völpel wrote:
Chuck Harris schrieb:


Capacitor oil is thin as water at 200F, and thick as syrup at
0F. You will find the capacitance changes between these two extremes,
but not really all that much. I don't think you will find that the
audio sounds "really hot" when the cap is at 200F, or has a "shivering"
sound when the cap is at 0F.




can you imagine the size of a foil-capacitor of 200F capacity?

the capacity of a paper/oil capacitor is just dependending on the size,
the number of turns and the thickness of the paper between the foil.
The oil is the same as for cooling transformers, some contain
dioxyn, so be careful.
The oil has almost always the same dielectric constant and is
just a simple cooling isolator nothing secret, just vegetable oil...

Peter

Chuck Harris schrieb:


Hi Chuck,

I guess I didn't make myself clear enough. By 200F
I meant 200 degrees Farenheit. That's a temperature,
not a capacitance value.

sorry, I understood capacity


And yes, I can imagine the size of a 200 farad oil-
capacitor. That, among other reasons is why I would
never propose using one in a vacuum tube audio application.

true


PCB laden oil does not contain dioxin. But it does
decompose to compounds that contain dioxin.

you are right with that explanation of PCB


regards

Peter

Hi Sander , West and others ,

I fail to see the comparison with the shock absorbers of a car.

The foil in the cap is trying to fibrate . Ever tried a crappy choke as a
choke-load ?
Same effect .... and the oil is damping that .
So if you wanna use oil and just have (room for) one , use it right behind
the rect. tube
since the ripple (and thus the fibration) is the greatest there ....

Groeten ,

Ronald .



Supply voltage regulation doesn't depend on the *kind* of cap that is
used.
BTW: my nice old Citroens CX and DS benefit greatly of the use of
fresh LHM in their hydraulic systems :-)
BTW2: ever heard of Peter van Willenswaard? He endorses the use of
old, massive oil caps whenever he can.
Read the old issues of Audio & Techniek for that!

--
Sander deWaal
Vacuum Audio Consultancy

The foil in the capacitor is *tightly* wound with paper between.
It isn't vibrating enough to measure. The oil wicks up into the
paper and improves the paper's dielectric constant, and voltage
breakdown characteristics.

Also, because each piece of foil has a piece of the opposing plate
on either side, the physical forces caused by the electrostatic
fields between the plates cancel.

Disk ceramics are a different beast, though, in the small high
capacity type with z5U dielectric, the dielectric is piezoelectric.
This means it swells and contracts with the voltage applied to the
capacitor. You can actually hear disk ceramic caps sing.

-Chuck

Ronald wrote:
Hi Sander , West and others ,


I fail to see the comparison with the shock absorbers of a car.


The foil in the cap is trying to fibrate . Ever tried a crappy choke as a
choke-load ?
Same effect .... and the oil is damping that .
So if you wanna use oil and just have (room for) one , use it right behind
the rect. tube
since the ripple (and thus the fibration) is the greatest there ....

Groeten ,

Ronald .

"Tim Williams" wrote in message ...

..... and free flowing oil between them to provide cooling.

Oil traps heat. How can it cool anything?

"Radium" wrote in message
om...
Oil traps heat. How can it cool anything?

Air is also a great insulator yet it manages to cool many things, often of
many kilowatts dissipation. It's called convection (or forced, if there's
a fan or pump).
For film + oil caps or any other similar type, this will have negligible
effect. But then most such caps aren't put through service anywhere near
as strenuous as would require it.

Tim

--
"That's for the courts to decide." - Homer Simpson
Website @ http://webpages.charter.net/dawill/tmoranwms

Hi RATs!

Oil traps heat. How can it cool anything?

Cool is a huge concept. Believe what you hear. What I hear with oil caps is
cool, to me.

Heat gets free, eventually

Happy Ears!
Al


Alan J. Marcy
Phoenix, AZ

PWC/mystic/Earhead

"Ronald" said:

The foil in the cap is trying to fibrate . Ever tried a crappy choke as a
choke-load ?
Same effect .... and the oil is damping that .
So if you wanna use oil and just have (room for) one , use it right behind
the rect. tube
since the ripple (and thus the fibration) is the greatest there ....

Said " vibration" would then be caused by electrostatic force, I
assume?
Applying your logic, both plates of the capacitor would be forced so
tight together by the DC voltage, that there's no chance they could
resonate because of the AC ripple.
A choke is an entirely different thing, because of magnetization of
the core, a force is applied to the core's lamels to resonate.
Last but not least, this magnetical effect is magnitudes larger than
the elctrodynamic effect you describe.

I'm sorry, but I don't buy into " scientifical" explanations of this
sort. I'm able to hear differences in caps, but not for the reason you
state.

--
Sander deWaal
Vacuum Audio Consultancy

In message , Chuck Harris
writes
The foil in the capacitor is *tightly* wound with paper between.
It isn't vibrating enough to measure. The oil wicks up into the
paper and improves the paper's dielectric constant, and voltage
breakdown characteristics.

Also, because each piece of foil has a piece of the opposing plate
on either side, the physical forces caused by the electrostatic
fields between the plates cancel.

Disk ceramics are a different beast, though, in the small high
capacity type with z5U dielectric, the dielectric is piezoelectric.
This means it swells and contracts with the voltage applied to the
capacitor. You can actually hear disk ceramic caps sing.

-Chuck


Yeah, I always say that an Y5V or Z5U SM ceramic does three things. As
well as a capacitor it's a microphone and a thermometer at the same
time.

BTW, have you ever looked at the curve of capacitance v applied dc
voltage for high-K ceramics? A lot of the high value SM ceramics are
down to about 30% of rated capacitance at full applied dc.
--
Chris Morriss

can you imagine the size of a foil-capacitor of 200F capacity?

You can measure it - they are sold, you know (though usually supplied as MOQs
from the factory). I regularly use 100uf polyprops I get from ICW as cathode
bypasses..

=== Andy Evans ===
Visit our Website:- http://www.artsandmedia.com
Audio, music and health pages and interesting links.

Chris Morriss wrote:

Yeah, I always say that an Y5V or Z5U SM ceramic does three things. As
well as a capacitor it's a microphone and a thermometer at the same time.

BTW, have you ever looked at the curve of capacitance v applied dc
voltage for high-K ceramics? A lot of the high value SM ceramics are
down to about 30% of rated capacitance at full applied dc.


I have seen this effect in two different instances where a cap was
misapplied. Once was my fault, and once in someone else's product.

This phenomenon drove me nuts when I was fixing an ultrasonic cleaner
that used a 1000pf, 5KV z5u ceramic cap as a resonator across the HV
transformer that drove the PZT. The problem was the cap changed its
value so much as it charged and discharged that the oscillator power
was greatly reduced (it was never tuned to resonance)

The case that was my fault was a coupling cap in an industrial
amplifier. The old one was a big paper cap, I replaced it with a
HV z5U cap. Jeeze Louise! That amplifier went nuts. Ringing,
singing, crazy unstable stuff. I swapped in a mylar, and it
settled right down and worked.

I used one as a thermometer (intentionally) once. I made a little
telemetry transmitter (just for grins) and I put a z5U in the tank
circuit. It caused the RF to change with temp, thus allowing the
temperature to be measured remotely. Nothing exciting, but I did
send it up in a balloon.

The only time I will use Z5U caps is as bypass on fairly stable DC
leads.

-Chuck Harris

Andy Evans wrote:
can you imagine the size of a foil-capacitor of 200F capacity?

You can measure it - they are sold, you know (though usually supplied as MOQs
from the factory). I regularly use 100uf polyprops I get from ICW as cathode
bypasses..

You have a long way to go from 100 *micro* farads to get to
200 farads!

-Chuck Harris