Home |
Search |
Today's Posts |
#1
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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. |
#2
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
"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. |
#3
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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. |
#4
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 .. |
#6
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
"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 |
#7
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
Casino Wolf wrote: They were very easy to roll and quality was a pleasant surprise. What do you mean by quality ? Graham |
#8
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 |
#9
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 |
#10
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 |
#11
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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. |
#12
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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. |
#13
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 |
#14
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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 |
#15
Posted to rec.antiques.radio+phono,rec.audio.tubes
|
|||
|
|||
Homebrew Capacitors Anyone?
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. |
Reply |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Homebrew selector | Tech | |||
Announcement: Building Homebrew Vacuum Tubes and Homebrew Transistors | Vacuum Tubes | |||
Power Transformer for Homebrew Resto | Vacuum Tubes | |||
sophomore needs help w/ homebrew Vox AC10 | Vacuum Tubes |