I think the DIY caps shouldn't be dismissed too quickly.
A power supply with all film caps would be doable and I would argue that those that say "just buy the things- thay are not that expensive" might balk at the price of film caps for this purpose.
How can a DIY'er not be tempted to REALLY DIY.
To get even tension- even with teflon, have the film pass under a roller with a weight on it. Roll the cap until the weight rises too high, then stop and unwind more from the supply. A tall ceiling migh help here!!!
I would be interested in film suppliers if anyone knows of any.
Especially polypropoline.
Also paper in oil could be enclosed in PVC pipe with endsaps.
Any suggestions for the paper type? Check the price of Jenson caps lately?
Resistors are easy- just wind some nichrome wire around a ceramic core- or maybe no core if the values are low.
Antique electronics supply sells nichrome in various gauges:
www.tubesandmore.com
A power supply with all film caps would be doable and I would argue that those that say "just buy the things- thay are not that expensive" might balk at the price of film caps for this purpose.
How can a DIY'er not be tempted to REALLY DIY.
To get even tension- even with teflon, have the film pass under a roller with a weight on it. Roll the cap until the weight rises too high, then stop and unwind more from the supply. A tall ceiling migh help here!!!
I would be interested in film suppliers if anyone knows of any.
Especially polypropoline.
Also paper in oil could be enclosed in PVC pipe with endsaps.
Any suggestions for the paper type? Check the price of Jenson caps lately?
Resistors are easy- just wind some nichrome wire around a ceramic core- or maybe no core if the values are low.
Antique electronics supply sells nichrome in various gauges:
www.tubesandmore.com
I'm not about to entertain the idea of rolling my own caps, but am interested in the fact that you guys are giving it a go.
Have you thought about using window tinting film? It has some properties that you will be interested in. I don't know what the resistance of the metallized type is, but it could be worth checking. Other types of metallized film are also available, used in packaging, graphic arts, and other applications.
Good luck!
Have you thought about using window tinting film? It has some properties that you will be interested in. I don't know what the resistance of the metallized type is, but it could be worth checking. Other types of metallized film are also available, used in packaging, graphic arts, and other applications.
Good luck!
I think the act of trying to start a 12 inch table saw by hand kind of defeats the purpose of having fingers doesn't it. There is no way I would turn it on and grab the blade to give it a spin.😀
Give the blade a good spin and then flick the on switch, no chopped off fingers. Not a good way, but at least you don't loose any body parts. Why are we discussing this though... 🙂
I can see FOX TV going for i.t
<center><font size="+3" color="#ff0000" face="Fantasy">When Capacitors Go Bad</font></center>
🙂
James
<center><font size="+3" color="#ff0000" face="Fantasy">When Capacitors Go Bad</font></center>
🙂
James
DIY Caps - Saran and Parchment Paper
I had a go with it yesterday -- using plates made of 86.6 sq inches aluminum foil and a slightly larger dielectric -- one Saran, the other uncoated parchment paper. I obtained C= 3.2nF, d= 0.008 for the Saran and C=4.1nF, d=0.02 for the parchment paper.
I had a go with it yesterday -- using plates made of 86.6 sq inches aluminum foil and a slightly larger dielectric -- one Saran, the other uncoated parchment paper. I obtained C= 3.2nF, d= 0.008 for the Saran and C=4.1nF, d=0.02 for the parchment paper.
Winding
I didn't, that is, the two surfaces were flat and I used a book to keep them in close contact. I suppose that you could use 3M spray adhesive, but this would, of course, change the dielectric constant.
I will have some time today to test with polyethylene and polypropylene and polyester (mylar). What I don't have is a micrometer to measure the guage of the plastics.
I didn't, that is, the two surfaces were flat and I used a book to keep them in close contact. I suppose that you could use 3M spray adhesive, but this would, of course, change the dielectric constant.
I will have some time today to test with polyethylene and polypropylene and polyester (mylar). What I don't have is a micrometer to measure the guage of the plastics.
I have some basic calipers that work pretty well even for this. Fold the film over itself 3 times, measure, divide by 8. Normal paper is nearly 2 mils thick, so even if you have only a 1-mil accurate caliper you can measure some pretty thin stuff with reasonable accuracy.
I would estimate my ~20nF saran-wrap cap to be the equivilent of 48 sq. inches...maybe your wrap is not as tight, or your saran-wrap is thicker?
I would estimate my ~20nF saran-wrap cap to be the equivilent of 48 sq. inches...maybe your wrap is not as tight, or your saran-wrap is thicker?
Saran thickness
I got an email back from SCJohnson -- they now own the Dow consumer brands -- regular Saran Wrap is 0.5 mils, Saran Plus is 0.52 mils.
I got an email back from SCJohnson -- they now own the Dow consumer brands -- regular Saran Wrap is 0.5 mils, Saran Plus is 0.52 mils.
Twisted
What a difference compression makes. I twisted the saran/aluminum combo into a tight rectangular shape. To squeeze out as much air as possible I used a couple Jorgensen clamps and sandwiched the DIY cap between two scraps of plexiglas. The area was smaller, this time 49 square inches, but the capacitance increased to just over 68nF ! (measured with a GR 1658).
I compared this DIY cap to a 68nF Orange Drop I had, the distortion was just at the HP339's residual level for the orange drop (0.002%), but the Saran DIY cap was about 0.0035%.
What a difference compression makes. I twisted the saran/aluminum combo into a tight rectangular shape. To squeeze out as much air as possible I used a couple Jorgensen clamps and sandwiched the DIY cap between two scraps of plexiglas. The area was smaller, this time 49 square inches, but the capacitance increased to just over 68nF ! (measured with a GR 1658).
I compared this DIY cap to a 68nF Orange Drop I had, the distortion was just at the HP339's residual level for the orange drop (0.002%), but the Saran DIY cap was about 0.0035%.
DIY Capacitor parts suppliers
You can get sheet copper and teflon from:
http://www.smallparts.com/
A stcked arangement might work nicely, no iductance, a square copper piece with a 1/2 inch tab on 1 corner could be used, the teflon piece should be aprox 1/8 inch larger than the square, apply 2 drops of wax to the teflon square, add the copper piece and heat with a clothes iron, add 2 drops of wax to the copper add the teflon, heat with iron repeat.
You can get sheet copper and teflon from:
http://www.smallparts.com/
A stcked arangement might work nicely, no iductance, a square copper piece with a 1/2 inch tab on 1 corner could be used, the teflon piece should be aprox 1/8 inch larger than the square, apply 2 drops of wax to the teflon square, add the copper piece and heat with a clothes iron, add 2 drops of wax to the copper add the teflon, heat with iron repeat.
Roll your own...
I've thought about making my own caps for crossovers.
PTFE and silver would be nice but copper or aluminium and polypropylene more practical. I'd roll them as tight as
possible with the two metal foil plates extending out beyond the insulation at each end so they can be crimped to give a
low inductance/resistance connection to the full length of both foils.
The main problems I think would be getting the capacitor dimensionally stable and doing a good job of crimping (or
whatever) the extended plates.
If the capacitor is in any way loose I think you'll get two sources of distortion.
Firstly it will act like a variable capacitance microphone, which is the last thing you want in a crossover!
Secondly, the varying electrostatic force between the plates will cause them to move so you get a voltage dependent
capacitance which is no good at all.
Crimping the extended foil would require some thought. Ideally you'd compress the loose spiral cylinder of foil down
around a wire until all air is expelled and the foil has coalesced into a short solid rod with all the foils faultlessly
connecting into it. In practice the best I can imagine is clamping flat in a vice as hard as possible, but unless a clamping
force is maintained I doubt the connections would be reliable, particularly with aluminium. In the case of copper the
clamped area could be lightly tinned before use so that when crimped the soft solder cold welds together. Might work.
Best of all would be copper or silver with PTFE insulation. Then you could flux and dip each end of the capacitor in a bath
of molten solder for excellent electrical connections. A small hole or two drilled through the foil spirals near to the
capacitor bodies would allow expanding air to escape rather than blow the solder out of the joints.
I've thought about making my own caps for crossovers.
PTFE and silver would be nice but copper or aluminium and polypropylene more practical. I'd roll them as tight as
possible with the two metal foil plates extending out beyond the insulation at each end so they can be crimped to give a
low inductance/resistance connection to the full length of both foils.
The main problems I think would be getting the capacitor dimensionally stable and doing a good job of crimping (or
whatever) the extended plates.
If the capacitor is in any way loose I think you'll get two sources of distortion.
Firstly it will act like a variable capacitance microphone, which is the last thing you want in a crossover!
Secondly, the varying electrostatic force between the plates will cause them to move so you get a voltage dependent
capacitance which is no good at all.
Crimping the extended foil would require some thought. Ideally you'd compress the loose spiral cylinder of foil down
around a wire until all air is expelled and the foil has coalesced into a short solid rod with all the foils faultlessly
connecting into it. In practice the best I can imagine is clamping flat in a vice as hard as possible, but unless a clamping
force is maintained I doubt the connections would be reliable, particularly with aluminium. In the case of copper the
clamped area could be lightly tinned before use so that when crimped the soft solder cold welds together. Might work.
Best of all would be copper or silver with PTFE insulation. Then you could flux and dip each end of the capacitor in a bath
of molten solder for excellent electrical connections. A small hole or two drilled through the foil spirals near to the
capacitor bodies would allow expanding air to escape rather than blow the solder out of the joints.
Polypropylene : Cheap and Easy Source
I meant to add that a good source of Polypropylene for experimental
capacitor building is this sort of parcel/box tape:
3M Clear Polypropylene Box Sealing Tape
I figure it's best to use the clear stuff. There are lots of branded and
unbranded tapes out there (see eBay) but in my experience
everything 3M make is very good quality so personally I'd 'stick'
🙂cannotbe: ) with them. Also, if they say it's Polypropylene then it
probably is. The adhesive will probably have some effect
unfortunately so I'd only want to use it for experimentation.
Perhaps it's the sort of glue that can be removed by a long soak in
water or maybe alcohol.
Hope this helps someone 🙂
BB
I meant to add that a good source of Polypropylene for experimental
capacitor building is this sort of parcel/box tape:
3M Clear Polypropylene Box Sealing Tape
I figure it's best to use the clear stuff. There are lots of branded and
unbranded tapes out there (see eBay) but in my experience
everything 3M make is very good quality so personally I'd 'stick'
🙂cannotbe: ) with them. Also, if they say it's Polypropylene then it
probably is. The adhesive will probably have some effect
unfortunately so I'd only want to use it for experimentation.
Perhaps it's the sort of glue that can be removed by a long soak in
water or maybe alcohol.
Hope this helps someone 🙂
BB
How about using Gertz inductors for the conductor? I know it is thicker than one might want, but it would just increase the size. Then you would have a high quality conductor. With a lathe you could run at a low speed and set up 4 spindles and use the lathe to wind them. You would only have to work out tension on the last piece of dielectric as it would pull the whole thing tight.
I wonder if it is worth it? I have some gertz inductors not being used. Hmmmmm....
I wonder if it is worth it? I have some gertz inductors not being used. Hmmmmm....
I also would like to know the source of this discussion. Very interesting it could be to know, how I make film caps arround 1000 until 10000 uF for replacing elcaps (electrolytics) in new amplifier projects.
here you will find finished high capacity foil versions:
http://www.kendeil.com/pdf/K33.pdf
http://www.kendeil.com/pdf/K31.pdf
http://www.powersmartsystems.ru/files/icar/lnk/LNK-P5X.pdf
Sondertypen - FTCap Fischer & Tausche Capacitors Group
and by post #2 about
http://www.diyaudio.com/forums/soli...ter-reference-amplifier-schematic-wanted.html
You will find that making caps that big, using the film available, will turn rather big, as in huge.
Why actually do so, as you can buy a better quality product, and even cheaper.
A few 150uF caps, and you're up there.
At some point I made a 5000uF pp film cap bank, just to see what it was good for.
It turned out to have no benefit over just having a few hundred uF PP film caps, and the rest of the capacitance in electrolytics of respectable quality.
Magura 🙂
i'm gonna give this a bash, I have reams of copper foil already that I use for filling spaces for compression terminations and for rudimentary ground plains and chunky traces on perf 😉 I had planned on getting some PTFE or delrin machined for mounting some regs in my dac (wank factor I know 😉 so will pick up some PTFE film while i'm there. great links in here for that BTW.
I will go with stacked form factor and encase it in phenolic paper (or thicker sheets of PTFE) before dipping in resin. I wish silver shim was more available in thinner gauges. I can import it from the states, but the minimum order is far more than I need.
its just for kicks and I will try them out in signal coupling where value and tolerance isnt quite as vital. works out quite cheap really when compared to Duelund. I will just leave a tab out each side and cover with resin after soldering some leads on.
should be fun
I will go with stacked form factor and encase it in phenolic paper (or thicker sheets of PTFE) before dipping in resin. I wish silver shim was more available in thinner gauges. I can import it from the states, but the minimum order is far more than I need.
its just for kicks and I will try them out in signal coupling where value and tolerance isnt quite as vital. works out quite cheap really when compared to Duelund. I will just leave a tab out each side and cover with resin after soldering some leads on.
should be fun
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