Yes, I did that some time ago using PTFE tape, beeswax, and a purpleheart tube (see earlier post). I will post some pictures tomorrow or the next day.
John
moamps said:
Hey Milan, thanks for that. I don't why it flew right over my head on first read. Last night I got around to measuring the capacitance between terminals and case of another metal-clad cap. 70 pf on a 0.1 uF model! Yikes. Unfortunately the body can't be stripped from these, however it can be taken into account during mounting. It does make a difference. Thx again.
I have the choice between Solen Fast, WIMA, Orange Drop, Black Gate standard, Panasonic P-series and ELNA Cerafine, what would you take for these?
<1µF - audio path
>1µF - audio path
<1µF - PSU, etc.
>1µF - PSU, etc.
For the PSU normal ceramics and electrolytics can be an option. Maybe some OSCONs also.
<1µF - audio path
>1µF - audio path
<1µF - PSU, etc.
>1µF - PSU, etc.
For the PSU normal ceramics and electrolytics can be an option. Maybe some OSCONs also.
dsavitsk said:
Panasonic makes a F&F poly cap with O2 free copper leads that I didn't see on your list. It is the ECQP(U) series on page 1297 in the DIGIKEY catalog. The problem is they only go up to .47uF and that is in the 400v range. They might be nice for linestage/preamp duty though.
Ftoroplast with foil is the best for audio. A first, a foil has low DC resistance. Second, ftoroplast has high dielectric permeability so they are relatively small, also ftoroplast is good dielectric with low leakage. Also, what is very significant for audio, it has low dielectric absorbtion that causes low non-linearities compared to other capacitors. Also, it needs very high temperature for destruction, but exposed to very high temperatures it starts generating Fosgen, it is a very poisoned gas. I am not sure that Ftoroplast is the same as Teflon, though...
Example of Ftoroplast capacitors is type K72P-5 made in Sanct Petersburg, Russia.
Also, there are so called Metal - film ftoroplast capacitors such as K72-9, they are worse than K72P-2 for audio, because of thin film layer that has higher DC resistance and non-linearities caused by metal and oxide small parts, but anyway they are much better than oil with paper caps such as bumble-bees and other similar vintage mass production.
Example of Ftoroplast capacitors is type K72P-5 made in Sanct Petersburg, Russia.
Also, there are so called Metal - film ftoroplast capacitors such as K72-9, they are worse than K72P-2 for audio, because of thin film layer that has higher DC resistance and non-linearities caused by metal and oxide small parts, but anyway they are much better than oil with paper caps such as bumble-bees and other similar vintage mass production.
Igor;
stripping caps you expose them on open air with a moisture. Better wrap it carefully. For example, polyethylene is one of the best dielectrics, but it is underestimated because it melts in low temperatures, so is unusable for military purposes, but great for home audio insulations.
--Anatoliy
stripping caps you expose them on open air with a moisture. Better wrap it carefully. For example, polyethylene is one of the best dielectrics, but it is underestimated because it melts in low temperatures, so is unusable for military purposes, but great for home audio insulations.
--Anatoliy
igormak said:
Wavebourn said:
Anatoliy, that's correct. But we are not in the sea, are'nt we? 😀
Steel around cap is worse, but other dielectrics compromise sound too. It is not in spite people choose wood cabinets as I did on the picture. Sounds better - just devil knows why.
These caps I use aprox 1 year and didn't get moisture yet. Where from could it sneak in tube amp? 😕
igormak said:
From the air. When you switch your amp on, it heats up. When you switch is off, it cools down and adsorbs the moisture.
Wavebourn said:
Ok, sure I know where from, just joking. But I prefer that risk. Simply change cap not a problem. As I told, have'nt got wet for a while. They was parafined very thick, i melt it down but could not avoid all stuff....
Souds very rich and deep, would advise to try silver & mica. Even in original boxes. Stripping add an air in sound, getting more space. Seems to be room expands. 🙂
There are static and dynamic dielectric permeabilities for the same matherials. It means, a capacitance will be different for DC and AC on different currents and frequencies. It means, transfer characteristics of a capacitor will depend on voltage, current, frequency. It means in turn, the more dependent is dielectric permeability on current, frequency, voltage, the more distortions you will get passing a signal through a capacitor.
Mica and ftoroplast are among the best.
Mica and ftoroplast are among the best.
Hi igormak, I share your preference for the SSG and bought a couple dozen 0.22 uF 0.3% before they disappeared from Ebay. Two questions, is the case aluminum or steel? The picture suggests aluminum. Also, did you mean the entire can is filled with wax?
One thing to watch, under high voltages silver can be prone to a phenomenon know as migration. It literally creeps across the surface of the dielectric and worst case short between layers. Seeing as the Russian Teflons maintain an air dielectric between cap and case if the silver micas are filled with wax I suspect it could, in part, have been to prevent migration. You might want to consider leaving a thin layer on the cap.
One thing to watch, under high voltages silver can be prone to a phenomenon know as migration. It literally creeps across the surface of the dielectric and worst case short between layers. Seeing as the Russian Teflons maintain an air dielectric between cap and case if the silver micas are filled with wax I suspect it could, in part, have been to prevent migration. You might want to consider leaving a thin layer on the cap.
Wavebourn said:
Pity, we are don't understand phicics of what a hell going in a cap wih sound 🙂 So, science could be unusable here. In practice very often the diffferent things happened. I wonder, meanwhile I'm radio engineer. Become very cautious and suspected.
rdf said:
Hi, RDF.
SGS is in steel. I buy them in Moscow quite easy, never tryed EBay.
Yes, the entire can is filled with wax and very tought.
As about migration.. there is a thinest wax layer.
How could this effect reflect itself do u think?
Igor.
igormak said:
They were in copper when I disassembled them being a kid. 😀
Also, there were a lot of line transformers with very thin permalloy; I discarded them because they were unusable for transistor power supplies. 😀
If you don't believe in Physics... Idunno.... But if believe a little bit, the silver is conductive...
Wavebourn said:
Are you shure it was SSG? It done for war (as everything 🙂), and russian militaries always feared radiation. They are steel and
thick enought. 🙂
Wavebourn said:
I believer, amin. But with some limitations where knowledge ends.
igormak said:
I haven't seen it myself however some in the antique radio restoration forums talk of the old unecapsulated mica capacitors eventually shorting out due to it. It's not certain and subject to some debate.
igormak said:
Also, I remember some diodes from NZ, like GD-401 (I am not sure). packed in lead envelopes...
rdf said:
Sure, I used to replace such mica caps inside of RF cans. But I thought that the initial source of leakage was caused by a moisture, then boiled up metal sealed the path.
Wavebourn said:
Yeah, 401's were very sensitive. All right, thank you guys for interesting discussion.
Igor.
In the presence of moisture and a potential, silver migrates across dielectric surfaces. This is a well-known problem in the PTF industry. No doubt that's why those old unencapsulated micas are failing.
- Status
- Not open for further replies.