[Casino Wolf]

Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

Here's an example of how I made one of the caps: for 0.02 uF (approx),
two sheets of 4.25" by 12" aluminum foil were stacked between three
sheets of 5" by 12.5" dielectric (grocery bags) material in the
following order: plastic - foil - plastic - foil - plastic. Edges
were folded over and taped down (you can trim off some of the plastic
if you wish, and use as little tape as possible). Two stranded wires,
each with 5 cm of insulation stripped-off at one end were inserted
into the appropriate layers for electrodes (insulated portions were
twisted together, sticking out of one of the 12" sides); no need to
solder or tape wires to the foil as they will be squeezed tightly in
place when the stack is folded and rolled. Then, the stack was folded
twice lengthwise, resulting in a strip 1/4 original width (i.e. about
1.25" by 12.5"), tightly rolled up and held together with tape.
Checked for shorts, measured capacitance, and tested for leakage at
HV. The leads can then be trimmed, soldered to solid wire and stuffed/
sealed into paper or plastic cylinders. With the exception of RF
circuits, exact cap values are usually not critical, so the homemade
0.02 uF cap can replace any leaky 0.01 to 0.05 cap.

They were very easy to roll and quality was a pleasant surprise. Not
to mention, cheap too! Tested all caps to 500VDC (max on my cap
tester) and not a single cap exhibited signs of leakage.

Cheers,

C.W.

[James Sweet]

"Casino Wolf" wrote in message
ups.com...
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

Here's an example of how I made one of the caps: for 0.02 uF (approx),
two sheets of 4.25" by 12" aluminum foil were stacked between three
sheets of 5" by 12.5" dielectric (grocery bags) material in the
following order: plastic - foil - plastic - foil - plastic. Edges
were folded over and taped down (you can trim off some of the plastic
if you wish, and use as little tape as possible). Two stranded wires,
each with 5 cm of insulation stripped-off at one end were inserted
into the appropriate layers for electrodes (insulated portions were
twisted together, sticking out of one of the 12" sides); no need to
solder or tape wires to the foil as they will be squeezed tightly in
place when the stack is folded and rolled. Then, the stack was folded
twice lengthwise, resulting in a strip 1/4 original width (i.e. about
1.25" by 12.5"), tightly rolled up and held together with tape.
Checked for shorts, measured capacitance, and tested for leakage at
HV. The leads can then be trimmed, soldered to solid wire and stuffed/
sealed into paper or plastic cylinders. With the exception of RF
circuits, exact cap values are usually not critical, so the homemade
0.02 uF cap can replace any leaky 0.01 to 0.05 cap.

They were very easy to roll and quality was a pleasant surprise. Not
to mention, cheap too! Tested all caps to 500VDC (max on my cap
tester) and not a single cap exhibited signs of leakage.

Cheers,

C.W.


I've done it just to see if it would work but I wouldn't bother building
capacitors for radio restoration, it's so cheap to just buy the real thing
and in some applications it could be a safety issue.. Might be fun to use
homemade capacitors in a completely homebrew radio though, all but the most
hardcore would have to settle with a ready made tube but pretty much
everything else one could reasonably make themselves.

[Patrick Turner]

James Sweet wrote:

"Casino Wolf" wrote in message
ups.com...
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

Here's an example of how I made one of the caps: for 0.02 uF (approx),
two sheets of 4.25" by 12" aluminum foil were stacked between three
sheets of 5" by 12.5" dielectric (grocery bags) material in the
following order: plastic - foil - plastic - foil - plastic. Edges
were folded over and taped down (you can trim off some of the plastic
if you wish, and use as little tape as possible). Two stranded wires,
each with 5 cm of insulation stripped-off at one end were inserted
into the appropriate layers for electrodes (insulated portions were
twisted together, sticking out of one of the 12" sides); no need to
solder or tape wires to the foil as they will be squeezed tightly in
place when the stack is folded and rolled. Then, the stack was folded
twice lengthwise, resulting in a strip 1/4 original width (i.e. about
1.25" by 12.5"), tightly rolled up and held together with tape.
Checked for shorts, measured capacitance, and tested for leakage at
HV. The leads can then be trimmed, soldered to solid wire and stuffed/
sealed into paper or plastic cylinders. With the exception of RF
circuits, exact cap values are usually not critical, so the homemade
0.02 uF cap can replace any leaky 0.01 to 0.05 cap.

They were very easy to roll and quality was a pleasant surprise. Not
to mention, cheap too! Tested all caps to 500VDC (max on my cap
tester) and not a single cap exhibited signs of leakage.

Cheers,

C.W.


I've done it just to see if it would work but I wouldn't bother building
capacitors for radio restoration, it's so cheap to just buy the real thing
and in some applications it could be a safety issue.. Might be fun to use
homemade capacitors in a completely homebrew radio though, all but the most
hardcore would have to settle with a ready made tube but pretty much
everything else one could reasonably make themselves.

I'd never both winding my own caps.

Having wires inserted between foils to get electrical contact
could be unreliable because of corrosion in the longer term espcially
with any DC present.

Plastic shopping bags don't make the best insulator and methinks some
sheet
teflon or polyester with copper foil would be better,and then the wires
could be soldered to the plates.
A 0.47uF rated for 630Vdc, ie, take 1,000V in a test will be a large
clunky home made cap.

Patrick Turner.

[Ernst]

On May 11, 2:02 am, Casino Wolf wrote:
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

I did in school, using teflon tape as a dielectric. Couple of things,
he The foil needs to be doubled back upon it self (inductance
issues); and an occasional slit made through the foil substrate (eddy
current issues). No clue on the program for spacinig of the slits, I
can tell you that the slits have to be made with an exceptionally
sharp exacto knife or a razor blade to preclude punching through the
dielectric.

A soda can wrapped with a quart ziplock bag, enclosed with an index
card clad in AL foil makes a decent tuning cap for a homebrew crystal
radio. Don't use Saran wrap! it's too "sticky".

Regards,

Ernst
..

[Jim Mueller]

The only problems I can see are that a pressure contact to aluminum isn't
reliable because the aluminum (and the copper wire too) oxidize in the
presence of air. That's why we solder connections, to keep air off. A
twisted connection will work without solder for a while.

A second problem would be the grocery bag. It isn't made for electrical
purposes and may have pinholes, especially after carrying groceries in it!

It's a fun exercise but too much work given the low cost (and small size) of
commercial capacitors

--
Jim Mueller

To get my real email address, replace wrongname with eportiz. Then replace
nospam with sacbeemail.

"Ernst" wrote in message
oups.com...
On May 11, 2:02 am, Casino Wolf wrote:
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

I did in school, using teflon tape as a dielectric. Couple of things,
he The foil needs to be doubled back upon it self (inductance
issues); and an occasional slit made through the foil substrate (eddy
current issues). No clue on the program for spacinig of the slits, I
can tell you that the slits have to be made with an exceptionally
sharp exacto knife or a razor blade to preclude punching through the
dielectric.

A soda can wrapped with a quart ziplock bag, enclosed with an index
card clad in AL foil makes a decent tuning cap for a homebrew crystal
radio. Don't use Saran wrap! it's too "sticky".

Regards,

Ernst
.

[Uncle Peter]

"Jim Mueller" wrote in message
...
The only problems I can see are that a pressure contact to aluminum isn't
reliable because the aluminum (and the copper wire too) oxidize in the
presence of air. That's why we solder connections, to keep air off. A
twisted connection will work without solder for a while.

A second problem would be the grocery bag. It isn't made for electrical
purposes and may have pinholes, especially after carrying groceries in it!

It's a fun exercise but too much work given the low cost (and small size)
of commercial capacitors

--
Jim Mueller


And the fact that most paper is hydroscopic and will eventually breakdown
and fail.

Pete

[Eeyore]

Casino Wolf wrote:

They were very easy to roll and quality was a pleasant surprise.

What do you mean by quality ?

Graham

[Engineer]

On May 11, 5:27 am, Patrick Turner wrote:
James Sweet wrote:

"Casino Wolf" wrote in message
oups.com...
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

Here's an example of how I made one of the caps: for 0.02 uF (approx),
two sheets of 4.25" by 12" aluminum foil were stacked between three
sheets of 5" by 12.5" dielectric (grocery bags) material in the
following order: plastic - foil - plastic - foil - plastic. Edges
were folded over and taped down (you can trim off some of the plastic
if you wish, and use as little tape as possible). Two stranded wires,
each with 5 cm of insulation stripped-off at one end were inserted
into the appropriate layers for electrodes (insulated portions were
twisted together, sticking out of one of the 12" sides); no need to
solder or tape wires to the foil as they will be squeezed tightly in
place when the stack is folded and rolled. Then, the stack was folded
twice lengthwise, resulting in a strip 1/4 original width (i.e. about
1.25" by 12.5"), tightly rolled up and held together with tape.
Checked for shorts, measured capacitance, and tested for leakage at
HV. The leads can then be trimmed, soldered to solid wire and stuffed/
sealed into paper or plastic cylinders. With the exception of RF
circuits, exact cap values are usually not critical, so the homemade
0.02 uF cap can replace any leaky 0.01 to 0.05 cap.

They were very easy to roll and quality was a pleasant surprise. Not
to mention, cheap too! Tested all caps to 500VDC (max on my cap
tester) and not a single cap exhibited signs of leakage.

Cheers,

C.W.

I've done it just to see if it would work but I wouldn't bother building
capacitors for radio restoration, it's so cheap to just buy the real thing
and in some applications it could be a safety issue.. Might be fun to use
homemade capacitors in a completely homebrew radio though, all but the most
hardcore would have to settle with a ready made tube but pretty much
everything else one could reasonably make themselves.

I'd never both winding my own caps.

Having wires inserted between foils to get electrical contact
could be unreliable because of corrosion in the longer term espcially
with any DC present.

Plastic shopping bags don't make the best insulator and methinks some
sheet
teflon or polyester with copper foil would be better,and then the wires
could be soldered to the plates.
A 0.47uF rated for 630Vdc, ie, take 1,000V in a test will be a large
clunky home made cap.

Patrick Turner.- Hide quoted text -

- Show quoted text -

Agreed... fun, but not practical unless you're on a desert island!
For the originallly proposed Al-Cu contact, how about this?
Wrap the Al foil around the clean Cu wire, then using a very blunt
knife, hammer a series of dents along the length to produce (I trust!)
a series of pressure welds.
I'm not sure about the stability of such an Al-Cu contact. Tthere are
many bad reports on Al house wiring but, IIRC, that's all about screws
loosening.
Cheers,
Roger

[Eeyore]

Engineer wrote:

There are many bad reports on Al house wiring but, IIRC, that's all about screws
loosening.

Cold flow of the conductor ?

Graham

[Casino Wolf]

Tested a few homebrew grocery bag caps in my Dynakit PAM-1 (both left
and right preamps) and I thought they're better than the SBE orange
drops I was using. Order of preference is as follows:
Old leaky caps (dangerous, but sounds great), grocery bag foil caps,
and orange drops.

C.W.

On May 12, 9:51 am, Eeyore
wrote:
Casino Wolf wrote:
They were very easy to roll and quality was a pleasant surprise.

What do you mean by quality ?

Graham

[Casino Wolf]

Wrap the Al foil around the clean Cu wire, then using a very blunt
knife, hammer a series of dents along the length to produce (I trust!)
a series of pressure welds....

Thanks, I'll try that.

[Jeffrey D Angus]

Casino Wolf wrote:

Tested a few homebrew grocery bag caps in my Dynakit PAM-1 (both left
and right preamps) and I thought they're better than the SBE orange
drops I was using. Order of preference is as follows:
Old leaky caps (dangerous, but sounds great), grocery bag foil caps,
and orange drops.

So, in other words, you're telling us that the grocery bag caps are
electrically just as bad as the 50 year old wax caps?

Jeff

--
RESTRICTED AREA. Anyone intruding shall immediately become subject to
the jurisdiction of military law. Intruders will be subject to lethal
force, without warning, and on sight. USE OF DEADLY FORCE IS AUTHORIZED
under the Internal Security Act of 1950.

[Ernst]

On May 12, 7:36 pm, Engineer wrote:

I'm not sure about the stability of such an Al-Cu contact. Tthere are
many bad reports on Al house wiring but, IIRC, that's all about screws

Well, yes and no. My parent's house, built in 1968 (Dallas, Texas) is
equiped with AL wire. There are a couple of problems with this:
First, AL does exhibit a significant expansion/contraction
characteristic compared to CU. 2nd, AL has a problem that is manifest
in dissimilar metal corrosion not realized with CU/Brass junctions.

I installed a dishwasher at my folks house, and happily cranked the
wire nuts down on CU/AL connections. Big mistake. Smoke and melted
plastic wire nuts resulted. I got a clue, and treated the connections
with DeoxIT (Caig Labs) compound the 2nd time around. Five years, no
problems.

Ernst

[Engineer]

On May 13, 12:36 pm, Ernst wrote:
On May 12, 7:36 pm, Engineer wrote:

I'm not sure about the stability of such an Al-Cu contact. Tthere are
many bad reports on Al house wiring but, IIRC, that's all about screws

Well, yes and no. My parent's house, built in 1968 (Dallas, Texas) is
equiped with AL wire. There are a couple of problems with this:
First, AL does exhibit a significant expansion/contraction
characteristic compared to CU. 2nd, AL has a problem that is manifest
in dissimilar metal corrosion not realized with CU/Brass junctions.

I installed a dishwasher at my folks house, and happily cranked the
wire nuts down on CU/AL connections. Big mistake. Smoke and melted
plastic wire nuts resulted. I got a clue, and treated the connections
with DeoxIT (Caig Labs) compound the 2nd time around. Five years, no
problems.

Ernst

Nasty business! For the record, I do NOT advocate mixing Al and Cu
wire, nor Al wire in Cu wire fixtures.
Cheers,
Roger

[RickH]

On May 11, 2:02 am, Casino Wolf wrote:
Hi All,

Just wondering does anyone roll their own capacitors for use in
homebrew projects, or as replacements for Black Beauties, Black Cats
and paper foils. I began rolling my own capacitors last week using
kitchen Al foil and plastic grocery bags (cut into sheets) as
dielectric.

Here's an example of how I made one of the caps: for 0.02 uF (approx),
two sheets of 4.25" by 12" aluminum foil were stacked between three
sheets of 5" by 12.5" dielectric (grocery bags) material in the
following order: plastic - foil - plastic - foil - plastic. Edges
were folded over and taped down (you can trim off some of the plastic
if you wish, and use as little tape as possible). Two stranded wires,
each with 5 cm of insulation stripped-off at one end were inserted
into the appropriate layers for electrodes (insulated portions were
twisted together, sticking out of one of the 12" sides); no need to
solder or tape wires to the foil as they will be squeezed tightly in
place when the stack is folded and rolled. Then, the stack was folded
twice lengthwise, resulting in a strip 1/4 original width (i.e. about
1.25" by 12.5"), tightly rolled up and held together with tape.
Checked for shorts, measured capacitance, and tested for leakage at
HV. The leads can then be trimmed, soldered to solid wire and stuffed/
sealed into paper or plastic cylinders. With the exception of RF
circuits, exact cap values are usually not critical, so the homemade
0.02 uF cap can replace any leaky 0.01 to 0.05 cap.

They were very easy to roll and quality was a pleasant surprise. Not
to mention, cheap too! Tested all caps to 500VDC (max on my cap
tester) and not a single cap exhibited signs of leakage.

Cheers,

C.W.

FYI modern grocery bags are bio-degradeable. But the whole idea
sounds like fun and probably a cool project for a boy interested in
electronics.