Here, I have used high grade, very thick long lasting packaging tape. This particular tape has a reputation for lasting quite long. I had some on the vinyl roof of my car, for almost a year. We have seasons here, too. Winter. So the tape is good enough to last. If not, simply re-wrap it. I do not expect to have an issue with this particular tape, any time soon. I'll look at the caps again, in a year, to check, but I doubt that the triple layer of tape will unwind any time soon.
The ends are filed with whatever epoxy suited my fancy, and was available. First, I used small piece of the leftover unwanted extra teflon film skin, and that was wadded up,and placed in the center hole that is at the ends of the cap. This was to seal the cap's core off so the epoxy would not creep into it. Next, I flattened the foil ends off with my fingernail, use what tools you feel you will need. This is also to prevent the epoxy from creeping in. Then, stand the caps on end, and fill with the epoxy, let dry, and do the same to the other ends. These are the 200V 0.1uf Russian teflon caps. Here they are drying, on the first end that has been filled:
The ends are filed with whatever epoxy suited my fancy, and was available. First, I used small piece of the leftover unwanted extra teflon film skin, and that was wadded up,and placed in the center hole that is at the ends of the cap. This was to seal the cap's core off so the epoxy would not creep into it. Next, I flattened the foil ends off with my fingernail, use what tools you feel you will need. This is also to prevent the epoxy from creeping in. Then, stand the caps on end, and fill with the epoxy, let dry, and do the same to the other ends. These are the 200V 0.1uf Russian teflon caps. Here they are drying, on the first end that has been filled:
An externally hosted image should be here but it was not working when we last tested it.
Those four caps in the photo, I epoxyed the other ends, and gave then to Anatech, when I visited him yesterday. He tested them on his HP cap tester at 100khz. We're still not sure they are registering any Dis. factor. Ie, it is so low ,it is virtually unmeasureable. And his HP is working, and it ain't a cheap one! Suffice it to say, as far as measurements go, the Russian Teflon caps measure nearly perfectly. I've no idea how they measure with their metal skins/can on, These ones are packaged exactly like thge ones in the photo. (they are the ones in the photo). They look very buff, and look like a standard finished commercial product. Very nice. The tape I wrapped them with, is alomost as thick as the electrical tape in the photo, and I used three layers, to be safe.
Hi KBK, thanks for the head's up on this. Until now I've prefered the Russian SSG silver micas to the teflons, feeling the latter had a bit too much artificial zing at the very top. Since a couple teflons in the pile were rusty due to improper storage they made perfect test subjects for a pin extraction.
I didn't go quiet as far as you and retained the case. The pins were extracted, the exposed wire sleeved with teflon tubing and the ends resealed with epoxy. Way too much epoxy got mixed, enough to completely flush the ends and damp the case a bit. Not only does removing almost 2" of highly magnetic steel conductor sound better (IMHO, no DBT, void where prohibited, blah, blah, blah), the 'zing' is gone and painted red the modified caps are dead ringers for 1/4 sticks of dynamite.
I didn't go quiet as far as you and retained the case. The pins were extracted, the exposed wire sleeved with teflon tubing and the ends resealed with epoxy. Way too much epoxy got mixed, enough to completely flush the ends and damp the case a bit. Not only does removing almost 2" of highly magnetic steel conductor sound better (IMHO, no DBT, void where prohibited, blah, blah, blah), the 'zing' is gone and painted red the modified caps are dead ringers for 1/4 sticks of dynamite.
The Russian teflon tweak that I linked a few pages back offers a number of advantages. One of the advantages that have not been touched on so far, but which is worth pointing out, is the elimination of the parasitic capacitance typically formed between the outer foil and the (removed) magnetic case. The capacitor that is housed inside the magnetic case is not firmly fixed to the case so it may move/vibrate, causing the value of the parasitic capacitance mentioned above to change. This may in turn result in modulations and distortions of the useful signal that passes through the capacitor - a sure no-go.
Another thing worth pointing out is that by placing the cap inside a cardboard tube we get excellent thermal and electrical isolation so the cap can be mounted onto the chassis, as shown in the picture below. Also, one should always take care to mark the end of the cap which is connected to the outer foil prior to tweaking the cap so that later, when the cap is eventually used in a circuit, that end can be connected to a lower impedance point (in most cases, this means that the cap would need to be connected to the output of the stage that precedes the cap rather than to the input of the stage that follows it).
Regards,
Milan
Another thing worth pointing out is that by placing the cap inside a cardboard tube we get excellent thermal and electrical isolation so the cap can be mounted onto the chassis, as shown in the picture below. Also, one should always take care to mark the end of the cap which is connected to the outer foil prior to tweaking the cap so that later, when the cap is eventually used in a circuit, that end can be connected to a lower impedance point (in most cases, this means that the cap would need to be connected to the output of the stage that precedes the cap rather than to the input of the stage that follows it).
Regards,
Milan
Hi Milan, thanks for the detailed shots. In return I think I can save you a ton of work. These caps just squeek into a 1 1/8" standard North American screw-feed pipe cutter like the one below. A larger size would be better but not worth more than the $12 I spent. A dozen turns and the end of the cap pops cleanly off. I cut just in the flange area to avoid contacting the internals. To save having to cut both ends work the pin loose on one side with pliers (never spinning the termninal relative to the body), desolder and pipe cut the opposite side.
For an outside sheath I'll probably go polypropylene or Teflon, both are available through McMaster-Carr.
For an outside sheath I'll probably go polypropylene or Teflon, both are available through McMaster-Carr.
Attachments
Well..that's smart! Another fine example of why they have design TEAMS, not individuals. There may be some ideas you may NOT have, whereas someone else will figure out a better way. And sooner. Using a pipe cutter. I'da never thunk of that one. Usually I'm one of the guys coming up with the 'way cool' method of doing a given thing. Not this time. 🙂
I did this a couple of months ago using PTFE tape and beeswax in the ends with teflon insulation on the leads. The adhesive used on the tape sticks to the teflon film on the Russian real well, so be careful because it won't come off without stretching it badly. I later made some purpleheart tubes for the caps for show.
John
John
KBK said:
No worries about your turf, I'm usually the guy with the clever shortcuts around effort. Forget what you've been told about neccesity, sloth is the mother of invention. 😴
rdf said:
Hi rdf:
That's a good idea!
It sent me rummaging through my plumming gear, looking for the clever thingie. And what do you know, it was right there at the bottom of the tools box! Thanks.Regards,
Milan
moamps said:
Wasn't sure about the European standards for plumbing, after all you have some pretty odd-looking porcelain bolted to the floors out there. Any further thoughts on the sheathing? I like the anti-microphonic properties of cardboard but not it's tendancy to absorb water. I also like the thought of filling most of the void with wax, epoxy, etc. and was surprised about how much empty space was in the original shell. No wonder the more extreme modders were resorting to modelling clay.
Hi Milan,
Sorry if a bit OT here... How do you like those Epcos 450V low esl/esr caps below compared to other lytics for B+ you've tried?
Great looking amp BTW. Nice chassis too.
regards,
fred
Sorry if a bit OT here... How do you like those Epcos 450V low esl/esr caps below compared to other lytics for B+ you've tried?
Great looking amp BTW. Nice chassis too.
regards,
fred
Hi rdf,
bcherry @ diyhifisupply carries some 0.1uF/500V silver micas. I don't know how they sound as I've not read any feedback yet regarding their performance. They're $56 for a pair though.
regards,
fred
rdf said:
I'm really not sure about the European standards either but I'm told we also use inches for plumbing pipes over here. I'm a radio guy like yourself, I believe (now I think I remember once having used a thing like the tube-cutter you referred to - a bit bigger, though - on an installation job, when I was setting up a huge radio and TV transmitting mast (1 7/8 inch cables). 😉
Yes, paper/cardboard is hygroscopic but I don't believe there is an actual danger here apart from your own perspiration (while laboring over the cap) or inspiration (e.g. beer). 😀
Regards,
Milan
P.S. I'm not quite sure what you meant by odd-looking porcelain. The whole thing is odd-looking if you ask me. 😀
fred76 said:
Hi fred:
In the tube (pre)amplifiers I built before the Siemox (e.g. SET6c33 etc.) I mainly used electrolytic caps salvaged from old switching power supplies. They were either Nichicons, Panasonics or Elnas and they were all very good. However, they are only rated for up to 400V and for the Siemox amplifier you just saw I needed caps rated for 450V. Epcos' turned out to be the best value for money I could find. They appear to work well too but I haven't really tried out any other caps in this particular setup so I can't tell how they would stand the comparison. I haven't been using the Siemox amplifier for long enough to be able to determine what to expect from the Epcos in the long run under such high-temperature conditions. So far so good - the amplifier works beautifully so I gather that means the Epcos can't be too bad either.
Glad you like the chassis; it's all DIY as well. Thank you for your kind words.
Regards,
Milan
moamps said:
Your memory is good, it's part of the standard RF tool kit. Ours is at a mountain-top site, otherwise I'ld still have $12!
I'm not sure I could get away with cardboard in Vancouver (4 months of continuous
in the winter) or in my home Ontario, where summer temps are given using the Humidex scale (30 C today, 42 with the Humidex.) Plus the always present inspirational fluid danger of course.
fred76 said:
Thanks Fred, a few sparse comments can be found on the diyhifisupply forum. Thorsten hinted at top-tier performance but I also recall partially rescinding that opinion of silver mica elsewhere. In my particular application, of the caps I've tried (Auricap, Wondercap, Orange Drops, K40Y9, NOS, etc.) the SSG and de-pinned Teflons are the only ones to date I liked at the high end, maintaining the natural punch and energy of real sibilance without added harshness or texture. For those inclined to risk it Ebay seller SOVCOM has the .2uF 5% 350 VDC silver micas back in stock for about $7 per. I was fortunate enough to pick up a couple dozen of the 0.3% equivalents back when they were much cheaper. Apparently the remainder have been scooped up by DIY suppliers charging way more.
My next project will see about 330 VDC across the coupling cap with another 100 VAC of swing. Much though I really like the micas I worry about them in the application. Now I have an alternative!
If you sit the cardboard tube in some melted beeswax, it should wick up the cardboard.
I have seen this done to the tubes from toilet rolls and used to raise seedings, just plant the tube in the ground it will decay in a few weeks.
Regards
James
Beeswax may work. If it's good enough for transformers, it should be good enough for caps. Come to think about it, I believe beeswax was indeed used in the old day to protect caps from moisture. It can be even more prefereable to epoxy where the operating temperature of the application allows it (I'm not sure but I think beeswax melts at about 60 degrees centigrade so extreme caution is advised).
Regards,
Milan
Regards,
Milan
Some waxes have excellent dielectric properties and I had considered using wax as filler between the cap and shell. It's not strong enough for my liking to hold the teflon tubing I use to sheath the end wires in place. Also, the two main filaments of this project each dissipate about 50 watts directly into heat. I'ld hate to find the caps puddled to the chassis bottom.
some VERY high voltage teflons have appeared on the bay, the usual sources. I've seen some of the mica caps myself, I always wondered about them. I've always been told to stay away from the mica caps. hhmmm. maybe so these folks could buy them all themselves? I've turned down many a silver/mica cap over the years, due to that comment.
As for the place the guys on ebay get their caps from, I think I found that spot. maybe. I've made contact with that guy once, about two weeks ago. The same source explains the numerical designations, so you can recognise the value/type of a cap, whereas someone else, even the seller, might not know what it is. Like the xxuf polystyrene caps. yummy!
I have about 400 of the polystyrene caps (250VDC) coming in soon. Not xxuf, mind you, but at 0.3uf(150), 0.399uf(100), 0.5uf(150) and the like, 400 of them is darn fine enough, thank you very much. I might be persuaded to share a few......
As for the place the guys on ebay get their caps from, I think I found that spot. maybe. I've made contact with that guy once, about two weeks ago. The same source explains the numerical designations, so you can recognise the value/type of a cap, whereas someone else, even the seller, might not know what it is. Like the xxuf polystyrene caps. yummy!
I have about 400 of the polystyrene caps (250VDC) coming in soon. Not xxuf, mind you, but at 0.3uf(150), 0.399uf(100), 0.5uf(150) and the like, 400 of them is darn fine enough, thank you very much. I might be persuaded to share a few......
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