New PIO Capacitor!

[serengetiplains]

Hey hey, today I received prototype samples of capacitors I had wound at an American capacitor firm. They're paper in oil types using Fluorinert FC-84 as the "oil," hence paper in Fluorinert, or PIF. Fluorinert is essentially liquid teflon, and the particular type of I'm using, FC-84, has a dielectric constant of 1.8, 10% better than teflon. My hat of to SY who tipped me off to Fluorinert.

The prototypes have been tested only for dissipation factor. The caps tested at a low 0.0055%, which beats the maximum specification for teflon by a factor of 4.

I'm currently ear testing the prototypes in my system, where they're performing duties bypassing 1uF solid teflon varieties as input caps to my cheap but wonderful sounding Charlizes. Initial impressions suggest the PIF, as I reasoned they might (should!), better normal-variety teflons.

I plan to have further caps wound using a different variety of Fluorinert, FC-72, which has a dielectric constant of 1.76. This cap will be a low temperature cap only because the boiling point of FC-72 is just a hair above room temperature (56 degrees C, actually).

I'm willing to have a quantity of caps wound to share with other DIY types, purchaseable at my cost. The best version I probably will have wound will be silver-foil/FC-72, if the cost of silver foil is not so prohibitive. Note that Fluorinert is very expensive, about $500 a gallon, gulp.

I only will proceed with these caps if my ears, and others' ears, tell me they're better than (solid) teflons. I'll keep you posted. In the mean-time, feel free to send any expressions of interest to me, and to post any comments here.

Anyone know where I can obtain some silver foil?

[cotdt]

i'm interested.


... but flurinert is sooooo expensive.

[cotdt]

remember to burn them in for 100 hours before testing them.

[serengetiplains]

By the way, anyone interested possibly in purchasing the final product kindly send me a PM. I'll keep track of you that way.

I'm not sure what values we can expect from reasonably sized designs. The caps I'm currently testing are 0.15uF and are 0.6"D x almost 2"L. They're wound with a thin layer of kraft paper, so cannot withstand transmitter tube voltages, to say the least. What values do people want/need?

Leads very likely will be short and silver.

[serengetiplains]

Originally posted by cotdt
remember to burn them in for 100 hours before testing them.

Hi cotdt, absolutely, I'll be burning in the caps I have for at least a week before I get down to serious listening.

[serengetiplains]

Here's one of the caps, this one being ~0.4uF, same size as the others. Nothing special, hey?

[cotdt]

that's beautiful. what about using some cheaper foil for the larger values? i'd imagine larger values are more useful, although .4 would be very useful as input caps.

[serengetiplains]

Cheaper varieties of foil are workable. The prototypes I have are aluminum foil. Up from aluminum, performance-wise, is tin, then silver which, I admit, is a bit excessive, but *would* offer better performance.

My point in posting this thread the way I have is to allow others to have access to what might be state of the art capacitors, so I certainly don't intend to push the price so high as to render the caps unaffordable to most.

Winding and materials, excluding the Fluorinert, probably will come in at $50 per cap, perhaps less, as the Fluorinert requires hermetic sealing and is a little difficult to work with (boils if you merely look at it). The manufacturer threw that number out as a possible base winding + materials cost, but really the question of cost is not well specified.

I'll probably have two varieties wound, one using FC-72, the other FC-84. From all interested, I need to know required voltage rating and uF.

[serengetiplains]

Originally posted by cotdt
that's beautiful. what about using some cheaper foil for the larger values? i'd imagine larger values are more useful, although .4 would be very useful as input caps.

As to larger values, sure, it's all just a question of size and cost.

[rdf]

What an experiment serengetiplains, DIY**2! Mighty impressive. The DF appears to support the notion the oil's the main dielectric in a PIO cap, the paper has little electrical impact and acts mostly as a carrier.