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In Reply to: RE: Teflon is cool.... posted by Stephen R on January 26, 2013 at 17:24:57
Well if you have a very high impedance grid circuit, perhaps. But in most baseband audio circuits I don't see any electrical benefit.What have you experienced?
Edits: 01/26/13Follow Ups:
I've built the same circuit on bare PCB vs the same layout on teflon in a phono circuit and ESL crossover; very different applications and both times I liked the teflon better. I wish I hadn't as it's more hassle.
I've tried the exact same circuit, a voltage regulator, on fibreglass PCB and teflon PCB and liked the teflon better. Again, not what I would have wanted.
Tests were done blind in the same amp. One channel one way, the other channel the other. Listen in mono to either.
Have done this a number of time with other people. Same results every time over a period of 30 years.
I don't bother any more as I don't use circuit boards like that. I now wire things up in the style of avionic instrumentation and aviation radio gear (where I served my apprenticeship) using teflon press through turret posts into a ground plane (unetched PCB)
Anyway, we all have our way of doing things. It's a recipe that works for me.
cheers,
Stephen
.
Not so much on 9 and 7 pin tubes, but there is voltage leakage across the pins on some octal base tubes. You see manufacturers combating this by molding ridges into the sockets between the pins to create longer pathways.
Stu
Yes I am familiar with the trick of adding ridges to reduce insulator voltage leakage. Just look at any power substation.
But do you honestly think that 1/16 in ridge on some octal is doing the same? I sincerely doubt it. It's for mechanical rigidity as far as I can see. after all Bakelite and Phenolic are quite brittle.
It's just cowboy logic again to make such an extrapolation without some solid data behind it.
and he posted, now you want "It's just cowboy logic again to make such an extrapolation without some solid data behind it."
Make up your mind.!
Follow the thread more carefully. I asked Stephen R what he experienced, not Stu.
on Pete Millet's website.
stu
That is extrapolating theory without understanding it.
Yes, the base material on octal tubes has more voltage leakage than an all glass tube.
Yes, the practice of rings and ridges on high voltage terminals does retard flashover and leakage by increasing the physical distance.
However that does not mean the small ridges on an octal tune base are there for leakage reduction. That is merely your guess.
IMPO, those ridges are mechanical support between the pins so the base doesn't break from the tube insertion force. The ridges are far too small to have any beneficial electrical benefit.
Just like your previous posts about group delay in black wire insulation you have no idea what the complex engineering terms you site really mean.
Why not get more electronics education before making these outlandish claims.
Try reading the material. You may learn something. But hell if I'm going to point out what was obvious in the references. If you think you know it all, fine with me.
Stu
That site has hundreds of pages of material in the form of old tube manuals. You expect me to read through all that?Why can't you just post a link to the page(s) where it states the ridges on octal tubes are for voltage leakage reduction? You must have read it there didn't you?
Why not just show it to us?
Or is this another false appeal to other authority?
Edits: 01/28/13
hints. I waded through significant amounts of the material he had and am thankful that Pete put it up.
I gave up spoon feeding babies decades ago.
You w\ant "proof", then do the research
You make an outlandish claim about tube base construction.
I challenge it.
You direct me to a site with hundreds of pages of old documentation and tell me it's in there but I have to find it myself.
You claim to know the information supporting your claim is there but won't share it with us?
Are you for real?
Repeat: I don't spoon feed babies anymore.
You have the site but don't want to read.
Too bad, you may learn something.
Stu, you are making a fool of yourself here.If you had solid documentation that the ridges on tube bases are for the purpose of voltage leakage you would have shoved it in my face 6 post's ago.
This "I read it but I'm not going to show it to you" is just silly. Anybody can see by now it's another phony claim of yours with absolutely no backing..
Edits: 01/28/13
...Eric Barbour discusses the ridges or "dams" in tube bases in his article on the 6550 and KT88 in issue #6 of Vacuum Tube Valley (winter, 1997). On page 22, column 3, paragraph 1 he states "Thanks to the large low-loss base with molded-in dams between the pins to discourage leakage currents, the 6550 was rated for 600 volts on the plate and 400 volts on the screen." I don't believe VTV back issues are on Millett's site and you may not consider Barbour an authority (he provides no references) but it's in writing and was published.
~!
The Mind has No Firewall~ U.S. Army War College.
forgot about that article, but Barbour did get it from elsewhere.Thanks again,
Stu
Edits: 01/30/13
No, I do consider Eric an authority and thanks for some valid documentation.
But I still question the effectiveness of 1/16in of additional distance. I know this can be calculated and perhaps has some advantage however small. I guess even 50 volts of additional capacity could be significant at 500 to 1000 volts.
It just seems to me that the barriers serve more of a structural purpose to support the center locating pin.
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