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how can test the stator insulation and mylar coating?
how can test the stator insulation and mylar coating?
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Old 7th April 2011, 04:22 PM   #11
geraldfryjr is offline geraldfryjr  United States
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Here are the ones when Charlie redid his panels with the new formual.




http://www.diyaudio.com/forums/plana...ml#post2174937


http://www.diyaudio.com/forums/plana...ml#post2401985

Cheers. jer
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Old 7th April 2011, 05:30 PM   #12
lutherblisset is offline lutherblisset  Italy
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Quote:
Originally Posted by geraldfryjr View Post
Over here in the states some of us have have been using a product called licron and licron crystal.

I first discovered "LICRON" in 2003 and "LICRON CRYSTAL" hit the market in about March of last year.

I don't know if it is avaiable in your area but I'm sure that a suitable equivalent can be found.
i'm trying to find this licron in my area but nothing for now (even on ebay and local web sites) maybe it's in some antistatic spray under different name...i'll ask to somebody who know this products
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Old 7th April 2011, 08:50 PM   #13
lutherblisset is offline lutherblisset  Italy
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I am a bit scared of very high tensions and except some tube amplifier i never worked with them. For the safety its better to built a high frequency bias supply like this:

http://sound.westhost.com/p105-f5.gif

or a tipical cockcroft-walton schematic? Anyway which are the things to avoid while running the tests?
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Old 7th April 2011, 10:26 PM   #14
geraldfryjr is offline geraldfryjr  United States
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I haven't tried that circuit yet but I have been wanting to.

Most are using a 2kv to 3kv supply.
I used such a high voltage because I was maxing everything out to find the absolute maximum limits of the materials.

On an average 3kv to 4kv is very sufficient.
The D/S spacing is the final determining factor here.

Charlie's "The Jazzmans blog" describes a very good simple bias supply.

Yes ,you can get a zapp from them but on the norm the actual currents are too low to be lethal.

Although as with all high voltage circuits "proper care and precautions and rules must be practiced and hendered too".

The voltages and current comming out of the stepup transformers are much more dangerous than the bias supply when driven to a high level.

If you are familar with tube circuits then you should already know the rules and I won't ponder on them.

I will dig up the schematic of my circuit and post it as the topology is no special secret.
It is a very simple switching type supply starting with 555 timer as well.

The only reason I haven't posted it yet was because I wanted to be sure that anyone could build it and have it work the first time one fired it up.

The only problem I have with it is that the resonate frequency of the transformer is right at the edge of the maximum frequency that the 555 can oscillate.

The transformers are just some little toriod cores that I salvaged out of some dead computer power supply's and are nothing special.

I have popped a couple of chips in the design process and found some that would not oscillate at those frequency's at all( >150khz).

But once tuned it proved very relieable and is variable from 0v to 7.5kv with a load.

It will build up a charge high enough to jump a 1cm gap and hold a continous D.C. arc at around 3mm to 4mm.
I have pictures of this in another thread.

I was also thinking about adding a feedback circuit aswell to help with constant regulation although it really isn't much of an issue but the circuit would allow a point for a safe voltage measurement using a DMM or a digital panel meter module.

Regards. jer
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Old 8th April 2011, 12:06 AM   #15
geraldfryjr is offline geraldfryjr  United States
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Here is the basic schematic of my bias supply.
Most values where found thru trial and error.
But most of them are as it sits now.
And this is for any one who wishes to use it. jer
Attached Images
File Type: jpg bias supply1.0.jpg (68.2 KB, 493 views)
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Old 8th April 2011, 03:08 AM   #16
alexberg is offline alexberg
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Quote:
Originally Posted by geraldfryjr View Post
Here is the basic schematic of my bias supply.
Most values where found thru trial and error.
But most of them are as it sits now.
And this is for any one who wishes to use it. jer
Ups, lets do it hard way when the easy one is on avail?!
I would not recommend using such design.
To be totally honest with you it's an example how not to do it.
Implementation kills the idea
Why don't you use two 230/12 trafos back to back? Medical grade.
Guaranteed isolation!
If one needs regulation, just put wirewound trimpot of 5-15 W as voltage divider in between(@12V). There is no power cosumption anyway...
If you insist upon superior qualities, then I would replace 555 and accociated "driver" of yours with IR2153, half bridge power topology would be reasonable as well.
What is the recovery time of the 1N4007? Go check for your own amusement.
Changing gate voltage for regulation is plain wrong, unless it's HF amplifier stage. May that's what you've discovered.

Last edited by alexberg; 8th April 2011 at 03:17 AM. Reason: putting it polite way
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Old 8th April 2011, 03:12 AM   #17
chinsettawong is offline chinsettawong  Thailand
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Hi,

I use Staticide 6300 for coating, and it works very well.

Wachara C.
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Old 8th April 2011, 06:47 AM   #18
geraldfryjr is offline geraldfryjr  United States
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Alex,the circuit works fine as is.

I will be changing the 555 to some other type of variable oscillator that has a wider and higher range for versatility.

I would have loved to use an IR2XXX mosfet driver but that would cost money and I don't have any.

But it sure would have made the design a whole lot easier as my intention was to use PWM for regulation.

A 15 watt wire wound pot would cost more than the all of the solid state devices in the circuit.

I do have a 50 watt 100 ohm wire wound pot that I was going to use but the element is open so I couldn't use it.

The typical recovery time of a 1N4007 is 2us and my very worst case (although marginal) requirement it is 5us.

I had questioned this myself but when I tested the output with a single diode I found that it was switched just fine so then I tested them with a full wave bridge and got I perfectly uniform fullwave rectified waveform across a resistance load.

My intent was not to have such a high switching frequency but thats the way it turned out because the cores I used were pulled and used as is and unmodified from dead computer switching supply's.

This version is a far cry from my original single mosfet design which grossely over heated and was extremely inefficient.
It took every bit of the 50 watts that supply transformer could muster up and ran quite hot because of it.

This version runs relieabily and the mofets are cool to the touch, Including the power transformer.

It is made of junk box parts and cost me next to nothing to build and I have enough parts to build six more but I only need two.

Yes there are alot of improvements that can be done and what is exactly wrong with the variable gate drive class b stage anyhow it works, it serves its purpose and serves it well.

Originaly I was going to vary the voltage supplying the mosfets but when I stumbled upon the output voltage of the 555 varying with the supply feeding it while maintianing its frequency, it just made things a whole lot easier.

It runs with about 300v of ripple at 7.5kv with a load thats 4% ripple.
That can be improved with a simple filter stage.
Much simpler than if it were running at 60hz and at >100khz you can't hear it anyway.

I have built many 60hz bias supply's and is why I had suggested that one should take a look at Charlie's web site " The Jazzmans blog " which describes a simple 60hz bias supply that works and works well.

I knew that I should not have posted my design as I had already stated that it was unfinished and needed to be improved so that if one did try to build it that it would work without a hitch.

As it took some tinkering to get it right, not knowing the parameters of the cores that I used.

My design was not intended to just only power ESL's with.
It was a great learning experience of the topology and I have plenty other uses planned with the design aswell.

Trust me I didn't just pop a few 555 chips, I took out a few mosfet along the way aswell.
Luckily they were dirt cheap and readily available at the local Radio shack or electronic parts store.
You can say that about the IRxxxx stuff.

Unforunately Radioshack is the only thing In my area and shipping for mail order would cost twice as much (if not more) as the cost of the parts I need at the moment.

After all, isn't it why they call it DIY?

Best regards. jer
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Old 8th April 2011, 03:17 PM   #19
alexberg is offline alexberg
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I did not say it does not work. Neither trying to step on your throat, so to speak. I've said it's improper way of doing things.
Eastern Germany's made Trabant falls into definition of a CAR. One guy travelled across the states on lawn mower
Is it a way to go?... For for other inexperienced guys to replicate?...
For instance 150kHz period is 6.7uS, half of that is 3.3 uS.
Use of diodes with 30uS recovery time which is 10 times longer than conduction time is plain wrong.
Attached Images
File Type: png 1n4007.png (122.5 KB, 442 views)

Last edited by alexberg; 8th April 2011 at 03:35 PM.
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Old 8th April 2011, 03:17 PM   #20
alexberg is offline alexberg
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Quote:
Originally Posted by chinsettawong View Post
Hi,

I use Staticide 6300 for coating, and it works very well.

Wachara C.
Have not you said it does not dry out?
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